1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice unmodified, this list of conditions, and the following
12 * disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 /*
30 * This file implements the ULE scheduler. ULE supports independent CPU
31 * run queues and fine grain locking. It has superior interactive
32 * performance under load even on uni-processor systems.
33 *
34 * etymology:
35 * ULE is the last three letters in schedule. It owes its name to a
36 * generic user created for a scheduling system by Paul Mikesell at
37 * Isilon Systems and a general lack of creativity on the part of the author.
38 */
39
40 #include <sys/cdefs.h>
41 #include "opt_hwpmc_hooks.h"
42 #include "opt_sched.h"
43
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/kdb.h>
47 #include <sys/kernel.h>
48 #include <sys/ktr.h>
49 #include <sys/limits.h>
50 #include <sys/lock.h>
51 #include <sys/mutex.h>
52 #include <sys/proc.h>
53 #include <sys/resource.h>
54 #include <sys/resourcevar.h>
55 #include <sys/sched.h>
56 #include <sys/sdt.h>
57 #include <sys/smp.h>
58 #include <sys/sx.h>
59 #include <sys/sysctl.h>
60 #include <sys/sysproto.h>
61 #include <sys/turnstile.h>
62 #include <sys/umtxvar.h>
63 #include <sys/vmmeter.h>
64 #include <sys/cpuset.h>
65 #include <sys/sbuf.h>
66
67 #ifdef HWPMC_HOOKS
68 #include <sys/pmckern.h>
69 #endif
70
71 #ifdef KDTRACE_HOOKS
72 #include <sys/dtrace_bsd.h>
73 int __read_mostly dtrace_vtime_active;
74 dtrace_vtime_switch_func_t dtrace_vtime_switch_func;
75 #endif
76
77 #include <machine/cpu.h>
78 #include <machine/smp.h>
79
80 #define KTR_ULE 0
81
82 #define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
83 #define TDQ_NAME_LEN (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU)))
84 #define TDQ_LOADNAME_LEN (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load"))
85
86 /*
87 * Thread scheduler specific section. All fields are protected
88 * by the thread lock.
89 */
90 struct td_sched {
91 struct runq *ts_runq; /* Run-queue we're queued on. */
92 short ts_flags; /* TSF_* flags. */
93 int ts_cpu; /* CPU that we have affinity for. */
94 int ts_rltick; /* Real last tick, for affinity. */
95 int ts_slice; /* Ticks of slice remaining. */
96 u_int ts_slptime; /* Number of ticks we vol. slept */
97 u_int ts_runtime; /* Number of ticks we were running */
98 int ts_ltick; /* Last tick that we were running on */
99 int ts_ftick; /* First tick that we were running on */
100 int ts_ticks; /* Tick count */
101 #ifdef KTR
102 char ts_name[TS_NAME_LEN];
103 #endif
104 };
105 /* flags kept in ts_flags */
106 #define TSF_BOUND 0x0001 /* Thread can not migrate. */
107 #define TSF_XFERABLE 0x0002 /* Thread was added as transferable. */
108
109 #define THREAD_CAN_MIGRATE(td) ((td)->td_pinned == 0)
110 #define THREAD_CAN_SCHED(td, cpu) \
111 CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
112
113 _Static_assert(sizeof(struct thread) + sizeof(struct td_sched) <=
114 sizeof(struct thread0_storage),
115 "increase struct thread0_storage.t0st_sched size");
116
117 /*
118 * Priority ranges used for interactive and non-interactive timeshare
119 * threads. The timeshare priorities are split up into four ranges.
120 * The first range handles interactive threads. The last three ranges
121 * (NHALF, x, and NHALF) handle non-interactive threads with the outer
122 * ranges supporting nice values.
123 */
124 #define PRI_TIMESHARE_RANGE (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
125 #define PRI_INTERACT_RANGE ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2)
126 #define PRI_BATCH_RANGE (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE)
127
128 #define PRI_MIN_INTERACT PRI_MIN_TIMESHARE
129 #define PRI_MAX_INTERACT (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1)
130 #define PRI_MIN_BATCH (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE)
131 #define PRI_MAX_BATCH PRI_MAX_TIMESHARE
132
133 /*
134 * Cpu percentage computation macros and defines.
135 *
136 * SCHED_TICK_SECS: Number of seconds to average the cpu usage across.
137 * SCHED_TICK_TARG: Number of hz ticks to average the cpu usage across.
138 * SCHED_TICK_MAX: Maximum number of ticks before scaling back.
139 * SCHED_TICK_SHIFT: Shift factor to avoid rounding away results.
140 * SCHED_TICK_HZ: Compute the number of hz ticks for a given ticks count.
141 * SCHED_TICK_TOTAL: Gives the amount of time we've been recording ticks.
142 */
143 #define SCHED_TICK_SECS 10
144 #define SCHED_TICK_TARG (hz * SCHED_TICK_SECS)
145 #define SCHED_TICK_MAX (SCHED_TICK_TARG + hz)
146 #define SCHED_TICK_SHIFT 10
147 #define SCHED_TICK_HZ(ts) ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
148 #define SCHED_TICK_TOTAL(ts) (max((ts)->ts_ltick - (ts)->ts_ftick, hz))
149
150 /*
151 * These macros determine priorities for non-interactive threads. They are
152 * assigned a priority based on their recent cpu utilization as expressed
153 * by the ratio of ticks to the tick total. NHALF priorities at the start
154 * and end of the MIN to MAX timeshare range are only reachable with negative
155 * or positive nice respectively.
156 *
157 * PRI_RANGE: Priority range for utilization dependent priorities.
158 * PRI_NRESV: Number of nice values.
159 * PRI_TICKS: Compute a priority in PRI_RANGE from the ticks count and total.
160 * PRI_NICE: Determines the part of the priority inherited from nice.
161 */
162 #define SCHED_PRI_NRESV (PRIO_MAX - PRIO_MIN)
163 #define SCHED_PRI_NHALF (SCHED_PRI_NRESV / 2)
164 #define SCHED_PRI_MIN (PRI_MIN_BATCH + SCHED_PRI_NHALF)
165 #define SCHED_PRI_MAX (PRI_MAX_BATCH - SCHED_PRI_NHALF)
166 #define SCHED_PRI_RANGE (SCHED_PRI_MAX - SCHED_PRI_MIN + 1)
167 #define SCHED_PRI_TICKS(ts) \
168 (SCHED_TICK_HZ((ts)) / \
169 (roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
170 #define SCHED_PRI_NICE(nice) (nice)
171
172 /*
173 * These determine the interactivity of a process. Interactivity differs from
174 * cpu utilization in that it expresses the voluntary time slept vs time ran
175 * while cpu utilization includes all time not running. This more accurately
176 * models the intent of the thread.
177 *
178 * SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
179 * before throttling back.
180 * SLP_RUN_FORK: Maximum slp+run time to inherit at fork time.
181 * INTERACT_MAX: Maximum interactivity value. Smaller is better.
182 * INTERACT_THRESH: Threshold for placement on the current runq.
183 */
184 #define SCHED_SLP_RUN_MAX ((hz * 5) << SCHED_TICK_SHIFT)
185 #define SCHED_SLP_RUN_FORK ((hz / 2) << SCHED_TICK_SHIFT)
186 #define SCHED_INTERACT_MAX (100)
187 #define SCHED_INTERACT_HALF (SCHED_INTERACT_MAX / 2)
188 #define SCHED_INTERACT_THRESH (30)
189
190 /*
191 * These parameters determine the slice behavior for batch work.
192 */
193 #define SCHED_SLICE_DEFAULT_DIVISOR 10 /* ~94 ms, 12 stathz ticks. */
194 #define SCHED_SLICE_MIN_DIVISOR 6 /* DEFAULT/MIN = ~16 ms. */
195
196 /* Flags kept in td_flags. */
197 #define TDF_PICKCPU TDF_SCHED0 /* Thread should pick new CPU. */
198 #define TDF_SLICEEND TDF_SCHED2 /* Thread time slice is over. */
199
200 /*
201 * tickincr: Converts a stathz tick into a hz domain scaled by
202 * the shift factor. Without the shift the error rate
203 * due to rounding would be unacceptably high.
204 * realstathz: stathz is sometimes 0 and run off of hz.
205 * sched_slice: Runtime of each thread before rescheduling.
206 * preempt_thresh: Priority threshold for preemption and remote IPIs.
207 */
208 static u_int __read_mostly sched_interact = SCHED_INTERACT_THRESH;
209 static int __read_mostly tickincr = 8 << SCHED_TICK_SHIFT;
210 static int __read_mostly realstathz = 127; /* reset during boot. */
211 static int __read_mostly sched_slice = 10; /* reset during boot. */
212 static int __read_mostly sched_slice_min = 1; /* reset during boot. */
213 #ifdef PREEMPTION
214 #ifdef FULL_PREEMPTION
215 static int __read_mostly preempt_thresh = PRI_MAX_IDLE;
216 #else
217 static int __read_mostly preempt_thresh = PRI_MIN_KERN;
218 #endif
219 #else
220 static int __read_mostly preempt_thresh = 0;
221 #endif
222 static int __read_mostly static_boost = PRI_MIN_BATCH;
223 static int __read_mostly sched_idlespins = 10000;
224 static int __read_mostly sched_idlespinthresh = -1;
225
226 /*
227 * tdq - per processor runqs and statistics. A mutex synchronizes access to
228 * most fields. Some fields are loaded or modified without the mutex.
229 *
230 * Locking protocols:
231 * (c) constant after initialization
232 * (f) flag, set with the tdq lock held, cleared on local CPU
233 * (l) all accesses are CPU-local
234 * (ls) stores are performed by the local CPU, loads may be lockless
235 * (t) all accesses are protected by the tdq mutex
236 * (ts) stores are serialized by the tdq mutex, loads may be lockless
237 */
238 struct tdq {
239 /*
240 * Ordered to improve efficiency of cpu_search() and switch().
241 * tdq_lock is padded to avoid false sharing with tdq_load and
242 * tdq_cpu_idle.
243 */
244 struct mtx_padalign tdq_lock; /* run queue lock. */
245 struct cpu_group *tdq_cg; /* (c) Pointer to cpu topology. */
246 struct thread *tdq_curthread; /* (t) Current executing thread. */
247 int tdq_load; /* (ts) Aggregate load. */
248 int tdq_sysload; /* (ts) For loadavg, !ITHD load. */
249 int tdq_cpu_idle; /* (ls) cpu_idle() is active. */
250 int tdq_transferable; /* (ts) Transferable thread count. */
251 short tdq_switchcnt; /* (l) Switches this tick. */
252 short tdq_oldswitchcnt; /* (l) Switches last tick. */
253 u_char tdq_lowpri; /* (ts) Lowest priority thread. */
254 u_char tdq_owepreempt; /* (f) Remote preemption pending. */
255 u_char tdq_idx; /* (t) Current insert index. */
256 u_char tdq_ridx; /* (t) Current removal index. */
257 int tdq_id; /* (c) cpuid. */
258 struct runq tdq_realtime; /* (t) real-time run queue. */
259 struct runq tdq_timeshare; /* (t) timeshare run queue. */
260 struct runq tdq_idle; /* (t) Queue of IDLE threads. */
261 char tdq_name[TDQ_NAME_LEN];
262 #ifdef KTR
263 char tdq_loadname[TDQ_LOADNAME_LEN];
264 #endif
265 };
266
267 /* Idle thread states and config. */
268 #define TDQ_RUNNING 1
269 #define TDQ_IDLE 2
270
271 /* Lockless accessors. */
272 #define TDQ_LOAD(tdq) atomic_load_int(&(tdq)->tdq_load)
273 #define TDQ_TRANSFERABLE(tdq) atomic_load_int(&(tdq)->tdq_transferable)
274 #define TDQ_SWITCHCNT(tdq) (atomic_load_short(&(tdq)->tdq_switchcnt) + \
275 atomic_load_short(&(tdq)->tdq_oldswitchcnt))
276 #define TDQ_SWITCHCNT_INC(tdq) (atomic_store_short(&(tdq)->tdq_switchcnt, \
277 atomic_load_short(&(tdq)->tdq_switchcnt) + 1))
278
279 #ifdef SMP
280 struct cpu_group __read_mostly *cpu_top; /* CPU topology */
281
282 #define SCHED_AFFINITY_DEFAULT (max(1, hz / 1000))
283 #define SCHED_AFFINITY(ts, t) ((ts)->ts_rltick > ticks - ((t) * affinity))
284
285 /*
286 * Run-time tunables.
287 */
288 static int rebalance = 1;
289 static int balance_interval = 128; /* Default set in sched_initticks(). */
290 static int __read_mostly affinity;
291 static int __read_mostly steal_idle = 1;
292 static int __read_mostly steal_thresh = 2;
293 static int __read_mostly always_steal = 0;
294 static int __read_mostly trysteal_limit = 2;
295
296 /*
297 * One thread queue per processor.
298 */
299 static struct tdq __read_mostly *balance_tdq;
300 static int balance_ticks;
301 DPCPU_DEFINE_STATIC(struct tdq, tdq);
302 DPCPU_DEFINE_STATIC(uint32_t, randomval);
303
304 #define TDQ_SELF() ((struct tdq *)PCPU_GET(sched))
305 #define TDQ_CPU(x) (DPCPU_ID_PTR((x), tdq))
306 #define TDQ_ID(x) ((x)->tdq_id)
307 #else /* !SMP */
308 static struct tdq tdq_cpu;
309
310 #define TDQ_ID(x) (0)
311 #define TDQ_SELF() (&tdq_cpu)
312 #define TDQ_CPU(x) (&tdq_cpu)
313 #endif
314
315 #define TDQ_LOCK_ASSERT(t, type) mtx_assert(TDQ_LOCKPTR((t)), (type))
316 #define TDQ_LOCK(t) mtx_lock_spin(TDQ_LOCKPTR((t)))
317 #define TDQ_LOCK_FLAGS(t, f) mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
318 #define TDQ_TRYLOCK(t) mtx_trylock_spin(TDQ_LOCKPTR((t)))
319 #define TDQ_TRYLOCK_FLAGS(t, f) mtx_trylock_spin_flags(TDQ_LOCKPTR((t)), (f))
320 #define TDQ_UNLOCK(t) mtx_unlock_spin(TDQ_LOCKPTR((t)))
321 #define TDQ_LOCKPTR(t) ((struct mtx *)(&(t)->tdq_lock))
322
323 static void sched_setpreempt(int);
324 static void sched_priority(struct thread *);
325 static void sched_thread_priority(struct thread *, u_char);
326 static int sched_interact_score(struct thread *);
327 static void sched_interact_update(struct thread *);
328 static void sched_interact_fork(struct thread *);
329 static void sched_pctcpu_update(struct td_sched *, int);
330
331 /* Operations on per processor queues */
332 static struct thread *tdq_choose(struct tdq *);
333 static void tdq_setup(struct tdq *, int i);
334 static void tdq_load_add(struct tdq *, struct thread *);
335 static void tdq_load_rem(struct tdq *, struct thread *);
336 static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
337 static __inline void tdq_runq_rem(struct tdq *, struct thread *);
338 static inline int sched_shouldpreempt(int, int, int);
339 static void tdq_print(int cpu);
340 static void runq_print(struct runq *rq);
341 static int tdq_add(struct tdq *, struct thread *, int);
342 #ifdef SMP
343 static int tdq_move(struct tdq *, struct tdq *);
344 static int tdq_idled(struct tdq *);
345 static void tdq_notify(struct tdq *, int lowpri);
346 static struct thread *tdq_steal(struct tdq *, int);
347 static struct thread *runq_steal(struct runq *, int);
348 static int sched_pickcpu(struct thread *, int);
349 static void sched_balance(void);
350 static bool sched_balance_pair(struct tdq *, struct tdq *);
351 static inline struct tdq *sched_setcpu(struct thread *, int, int);
352 static inline void thread_unblock_switch(struct thread *, struct mtx *);
353 static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
354 static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb,
355 struct cpu_group *cg, int indent);
356 #endif
357
358 static void sched_setup(void *dummy);
359 SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
360
361 static void sched_initticks(void *dummy);
362 SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
363 NULL);
364
365 SDT_PROVIDER_DEFINE(sched);
366
367 SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *",
368 "struct proc *", "uint8_t");
369 SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *",
370 "struct proc *", "void *");
371 SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *",
372 "struct proc *", "void *", "int");
373 SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *",
374 "struct proc *", "uint8_t", "struct thread *");
375 SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
376 SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *",
377 "struct proc *");
378 SDT_PROBE_DEFINE(sched, , , on__cpu);
379 SDT_PROBE_DEFINE(sched, , , remain__cpu);
380 SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *",
381 "struct proc *");
382
383 /*
384 * Print the threads waiting on a run-queue.
385 */
386 static void
runq_print(struct runq * rq)387 runq_print(struct runq *rq)
388 {
389 struct rqhead *rqh;
390 struct thread *td;
391 int pri;
392 int j;
393 int i;
394
395 for (i = 0; i < RQB_LEN; i++) {
396 printf("\t\trunq bits %d 0x%zx\n",
397 i, rq->rq_status.rqb_bits[i]);
398 for (j = 0; j < RQB_BPW; j++)
399 if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
400 pri = j + (i << RQB_L2BPW);
401 rqh = &rq->rq_queues[pri];
402 TAILQ_FOREACH(td, rqh, td_runq) {
403 printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
404 td, td->td_name, td->td_priority,
405 td->td_rqindex, pri);
406 }
407 }
408 }
409 }
410
411 /*
412 * Print the status of a per-cpu thread queue. Should be a ddb show cmd.
413 */
414 static void __unused
tdq_print(int cpu)415 tdq_print(int cpu)
416 {
417 struct tdq *tdq;
418
419 tdq = TDQ_CPU(cpu);
420
421 printf("tdq %d:\n", TDQ_ID(tdq));
422 printf("\tlock %p\n", TDQ_LOCKPTR(tdq));
423 printf("\tLock name: %s\n", tdq->tdq_name);
424 printf("\tload: %d\n", tdq->tdq_load);
425 printf("\tswitch cnt: %d\n", tdq->tdq_switchcnt);
426 printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
427 printf("\ttimeshare idx: %d\n", tdq->tdq_idx);
428 printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
429 printf("\tload transferable: %d\n", tdq->tdq_transferable);
430 printf("\tlowest priority: %d\n", tdq->tdq_lowpri);
431 printf("\trealtime runq:\n");
432 runq_print(&tdq->tdq_realtime);
433 printf("\ttimeshare runq:\n");
434 runq_print(&tdq->tdq_timeshare);
435 printf("\tidle runq:\n");
436 runq_print(&tdq->tdq_idle);
437 }
438
439 static inline int
sched_shouldpreempt(int pri,int cpri,int remote)440 sched_shouldpreempt(int pri, int cpri, int remote)
441 {
442 /*
443 * If the new priority is not better than the current priority there is
444 * nothing to do.
445 */
446 if (pri >= cpri)
447 return (0);
448 /*
449 * Always preempt idle.
450 */
451 if (cpri >= PRI_MIN_IDLE)
452 return (1);
453 /*
454 * If preemption is disabled don't preempt others.
455 */
456 if (preempt_thresh == 0)
457 return (0);
458 /*
459 * Preempt if we exceed the threshold.
460 */
461 if (pri <= preempt_thresh)
462 return (1);
463 /*
464 * If we're interactive or better and there is non-interactive
465 * or worse running preempt only remote processors.
466 */
467 if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
468 return (1);
469 return (0);
470 }
471
472 /*
473 * Add a thread to the actual run-queue. Keeps transferable counts up to
474 * date with what is actually on the run-queue. Selects the correct
475 * queue position for timeshare threads.
476 */
477 static __inline void
tdq_runq_add(struct tdq * tdq,struct thread * td,int flags)478 tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
479 {
480 struct td_sched *ts;
481 u_char pri;
482
483 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
484 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
485
486 pri = td->td_priority;
487 ts = td_get_sched(td);
488 TD_SET_RUNQ(td);
489 if (THREAD_CAN_MIGRATE(td)) {
490 tdq->tdq_transferable++;
491 ts->ts_flags |= TSF_XFERABLE;
492 }
493 if (pri < PRI_MIN_BATCH) {
494 ts->ts_runq = &tdq->tdq_realtime;
495 } else if (pri <= PRI_MAX_BATCH) {
496 ts->ts_runq = &tdq->tdq_timeshare;
497 KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
498 ("Invalid priority %d on timeshare runq", pri));
499 /*
500 * This queue contains only priorities between MIN and MAX
501 * batch. Use the whole queue to represent these values.
502 */
503 if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
504 pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
505 pri = (pri + tdq->tdq_idx) % RQ_NQS;
506 /*
507 * This effectively shortens the queue by one so we
508 * can have a one slot difference between idx and
509 * ridx while we wait for threads to drain.
510 */
511 if (tdq->tdq_ridx != tdq->tdq_idx &&
512 pri == tdq->tdq_ridx)
513 pri = (unsigned char)(pri - 1) % RQ_NQS;
514 } else
515 pri = tdq->tdq_ridx;
516 runq_add_pri(ts->ts_runq, td, pri, flags);
517 return;
518 } else
519 ts->ts_runq = &tdq->tdq_idle;
520 runq_add(ts->ts_runq, td, flags);
521 }
522
523 /*
524 * Remove a thread from a run-queue. This typically happens when a thread
525 * is selected to run. Running threads are not on the queue and the
526 * transferable count does not reflect them.
527 */
528 static __inline void
tdq_runq_rem(struct tdq * tdq,struct thread * td)529 tdq_runq_rem(struct tdq *tdq, struct thread *td)
530 {
531 struct td_sched *ts;
532
533 ts = td_get_sched(td);
534 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
535 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
536 KASSERT(ts->ts_runq != NULL,
537 ("tdq_runq_remove: thread %p null ts_runq", td));
538 if (ts->ts_flags & TSF_XFERABLE) {
539 tdq->tdq_transferable--;
540 ts->ts_flags &= ~TSF_XFERABLE;
541 }
542 if (ts->ts_runq == &tdq->tdq_timeshare) {
543 if (tdq->tdq_idx != tdq->tdq_ridx)
544 runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
545 else
546 runq_remove_idx(ts->ts_runq, td, NULL);
547 } else
548 runq_remove(ts->ts_runq, td);
549 }
550
551 /*
552 * Load is maintained for all threads RUNNING and ON_RUNQ. Add the load
553 * for this thread to the referenced thread queue.
554 */
555 static void
tdq_load_add(struct tdq * tdq,struct thread * td)556 tdq_load_add(struct tdq *tdq, struct thread *td)
557 {
558
559 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
560 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
561
562 tdq->tdq_load++;
563 if ((td->td_flags & TDF_NOLOAD) == 0)
564 tdq->tdq_sysload++;
565 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
566 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
567 }
568
569 /*
570 * Remove the load from a thread that is transitioning to a sleep state or
571 * exiting.
572 */
573 static void
tdq_load_rem(struct tdq * tdq,struct thread * td)574 tdq_load_rem(struct tdq *tdq, struct thread *td)
575 {
576
577 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
578 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
579 KASSERT(tdq->tdq_load != 0,
580 ("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
581
582 tdq->tdq_load--;
583 if ((td->td_flags & TDF_NOLOAD) == 0)
584 tdq->tdq_sysload--;
585 KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
586 SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
587 }
588
589 /*
590 * Bound timeshare latency by decreasing slice size as load increases. We
591 * consider the maximum latency as the sum of the threads waiting to run
592 * aside from curthread and target no more than sched_slice latency but
593 * no less than sched_slice_min runtime.
594 */
595 static inline int
tdq_slice(struct tdq * tdq)596 tdq_slice(struct tdq *tdq)
597 {
598 int load;
599
600 /*
601 * It is safe to use sys_load here because this is called from
602 * contexts where timeshare threads are running and so there
603 * cannot be higher priority load in the system.
604 */
605 load = tdq->tdq_sysload - 1;
606 if (load >= SCHED_SLICE_MIN_DIVISOR)
607 return (sched_slice_min);
608 if (load <= 1)
609 return (sched_slice);
610 return (sched_slice / load);
611 }
612
613 /*
614 * Set lowpri to its exact value by searching the run-queue and
615 * evaluating curthread. curthread may be passed as an optimization.
616 */
617 static void
tdq_setlowpri(struct tdq * tdq,struct thread * ctd)618 tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
619 {
620 struct thread *td;
621
622 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
623 if (ctd == NULL)
624 ctd = tdq->tdq_curthread;
625 td = tdq_choose(tdq);
626 if (td == NULL || td->td_priority > ctd->td_priority)
627 tdq->tdq_lowpri = ctd->td_priority;
628 else
629 tdq->tdq_lowpri = td->td_priority;
630 }
631
632 #ifdef SMP
633 /*
634 * We need some randomness. Implement a classic Linear Congruential
635 * Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for
636 * m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits
637 * of the random state (in the low bits of our answer) to keep
638 * the maximum randomness.
639 */
640 static uint32_t
sched_random(void)641 sched_random(void)
642 {
643 uint32_t *rndptr;
644
645 rndptr = DPCPU_PTR(randomval);
646 *rndptr = *rndptr * 69069 + 5;
647
648 return (*rndptr >> 16);
649 }
650
651 struct cpu_search {
652 cpuset_t *cs_mask; /* The mask of allowed CPUs to choose from. */
653 int cs_prefer; /* Prefer this CPU and groups including it. */
654 int cs_running; /* The thread is now running at cs_prefer. */
655 int cs_pri; /* Min priority for low. */
656 int cs_load; /* Max load for low, min load for high. */
657 int cs_trans; /* Min transferable load for high. */
658 };
659
660 struct cpu_search_res {
661 int csr_cpu; /* The best CPU found. */
662 int csr_load; /* The load of cs_cpu. */
663 };
664
665 /*
666 * Search the tree of cpu_groups for the lowest or highest loaded CPU.
667 * These routines actually compare the load on all paths through the tree
668 * and find the least loaded cpu on the least loaded path, which may differ
669 * from the least loaded cpu in the system. This balances work among caches
670 * and buses.
671 */
672 static int
cpu_search_lowest(const struct cpu_group * cg,const struct cpu_search * s,struct cpu_search_res * r)673 cpu_search_lowest(const struct cpu_group *cg, const struct cpu_search *s,
674 struct cpu_search_res *r)
675 {
676 struct cpu_search_res lr;
677 struct tdq *tdq;
678 int c, bload, l, load, p, total;
679
680 total = 0;
681 bload = INT_MAX;
682 r->csr_cpu = -1;
683
684 /* Loop through children CPU groups if there are any. */
685 if (cg->cg_children > 0) {
686 for (c = cg->cg_children - 1; c >= 0; c--) {
687 load = cpu_search_lowest(&cg->cg_child[c], s, &lr);
688 total += load;
689
690 /*
691 * When balancing do not prefer SMT groups with load >1.
692 * It allows round-robin between SMT groups with equal
693 * load within parent group for more fair scheduling.
694 */
695 if (__predict_false(s->cs_running) &&
696 (cg->cg_child[c].cg_flags & CG_FLAG_THREAD) &&
697 load >= 128 && (load & 128) != 0)
698 load += 128;
699
700 if (lr.csr_cpu >= 0 && (load < bload ||
701 (load == bload && lr.csr_load < r->csr_load))) {
702 bload = load;
703 r->csr_cpu = lr.csr_cpu;
704 r->csr_load = lr.csr_load;
705 }
706 }
707 return (total);
708 }
709
710 /* Loop through children CPUs otherwise. */
711 for (c = cg->cg_last; c >= cg->cg_first; c--) {
712 if (!CPU_ISSET(c, &cg->cg_mask))
713 continue;
714 tdq = TDQ_CPU(c);
715 l = TDQ_LOAD(tdq);
716 if (c == s->cs_prefer) {
717 if (__predict_false(s->cs_running))
718 l--;
719 p = 128;
720 } else
721 p = 0;
722 load = l * 256;
723 total += load - p;
724
725 /*
726 * Check this CPU is acceptable.
727 * If the threads is already on the CPU, don't look on the TDQ
728 * priority, since it can be the priority of the thread itself.
729 */
730 if (l > s->cs_load ||
731 (atomic_load_char(&tdq->tdq_lowpri) <= s->cs_pri &&
732 (!s->cs_running || c != s->cs_prefer)) ||
733 !CPU_ISSET(c, s->cs_mask))
734 continue;
735
736 /*
737 * When balancing do not prefer CPUs with load > 1.
738 * It allows round-robin between CPUs with equal load
739 * within the CPU group for more fair scheduling.
740 */
741 if (__predict_false(s->cs_running) && l > 0)
742 p = 0;
743
744 load -= sched_random() % 128;
745 if (bload > load - p) {
746 bload = load - p;
747 r->csr_cpu = c;
748 r->csr_load = load;
749 }
750 }
751 return (total);
752 }
753
754 static int
cpu_search_highest(const struct cpu_group * cg,const struct cpu_search * s,struct cpu_search_res * r)755 cpu_search_highest(const struct cpu_group *cg, const struct cpu_search *s,
756 struct cpu_search_res *r)
757 {
758 struct cpu_search_res lr;
759 struct tdq *tdq;
760 int c, bload, l, load, total;
761
762 total = 0;
763 bload = INT_MIN;
764 r->csr_cpu = -1;
765
766 /* Loop through children CPU groups if there are any. */
767 if (cg->cg_children > 0) {
768 for (c = cg->cg_children - 1; c >= 0; c--) {
769 load = cpu_search_highest(&cg->cg_child[c], s, &lr);
770 total += load;
771 if (lr.csr_cpu >= 0 && (load > bload ||
772 (load == bload && lr.csr_load > r->csr_load))) {
773 bload = load;
774 r->csr_cpu = lr.csr_cpu;
775 r->csr_load = lr.csr_load;
776 }
777 }
778 return (total);
779 }
780
781 /* Loop through children CPUs otherwise. */
782 for (c = cg->cg_last; c >= cg->cg_first; c--) {
783 if (!CPU_ISSET(c, &cg->cg_mask))
784 continue;
785 tdq = TDQ_CPU(c);
786 l = TDQ_LOAD(tdq);
787 load = l * 256;
788 total += load;
789
790 /*
791 * Check this CPU is acceptable.
792 */
793 if (l < s->cs_load || TDQ_TRANSFERABLE(tdq) < s->cs_trans ||
794 !CPU_ISSET(c, s->cs_mask))
795 continue;
796
797 load -= sched_random() % 256;
798 if (load > bload) {
799 bload = load;
800 r->csr_cpu = c;
801 }
802 }
803 r->csr_load = bload;
804 return (total);
805 }
806
807 /*
808 * Find the cpu with the least load via the least loaded path that has a
809 * lowpri greater than pri pri. A pri of -1 indicates any priority is
810 * acceptable.
811 */
812 static inline int
sched_lowest(const struct cpu_group * cg,cpuset_t * mask,int pri,int maxload,int prefer,int running)813 sched_lowest(const struct cpu_group *cg, cpuset_t *mask, int pri, int maxload,
814 int prefer, int running)
815 {
816 struct cpu_search s;
817 struct cpu_search_res r;
818
819 s.cs_prefer = prefer;
820 s.cs_running = running;
821 s.cs_mask = mask;
822 s.cs_pri = pri;
823 s.cs_load = maxload;
824 cpu_search_lowest(cg, &s, &r);
825 return (r.csr_cpu);
826 }
827
828 /*
829 * Find the cpu with the highest load via the highest loaded path.
830 */
831 static inline int
sched_highest(const struct cpu_group * cg,cpuset_t * mask,int minload,int mintrans)832 sched_highest(const struct cpu_group *cg, cpuset_t *mask, int minload,
833 int mintrans)
834 {
835 struct cpu_search s;
836 struct cpu_search_res r;
837
838 s.cs_mask = mask;
839 s.cs_load = minload;
840 s.cs_trans = mintrans;
841 cpu_search_highest(cg, &s, &r);
842 return (r.csr_cpu);
843 }
844
845 static void
sched_balance_group(struct cpu_group * cg)846 sched_balance_group(struct cpu_group *cg)
847 {
848 struct tdq *tdq;
849 struct thread *td;
850 cpuset_t hmask, lmask;
851 int high, low, anylow;
852
853 CPU_FILL(&hmask);
854 for (;;) {
855 high = sched_highest(cg, &hmask, 1, 0);
856 /* Stop if there is no more CPU with transferrable threads. */
857 if (high == -1)
858 break;
859 CPU_CLR(high, &hmask);
860 CPU_COPY(&hmask, &lmask);
861 /* Stop if there is no more CPU left for low. */
862 if (CPU_EMPTY(&lmask))
863 break;
864 tdq = TDQ_CPU(high);
865 if (TDQ_LOAD(tdq) == 1) {
866 /*
867 * There is only one running thread. We can't move
868 * it from here, so tell it to pick new CPU by itself.
869 */
870 TDQ_LOCK(tdq);
871 td = tdq->tdq_curthread;
872 if (td->td_lock == TDQ_LOCKPTR(tdq) &&
873 (td->td_flags & TDF_IDLETD) == 0 &&
874 THREAD_CAN_MIGRATE(td)) {
875 td->td_flags |= TDF_PICKCPU;
876 ast_sched_locked(td, TDA_SCHED);
877 if (high != curcpu)
878 ipi_cpu(high, IPI_AST);
879 }
880 TDQ_UNLOCK(tdq);
881 break;
882 }
883 anylow = 1;
884 nextlow:
885 if (TDQ_TRANSFERABLE(tdq) == 0)
886 continue;
887 low = sched_lowest(cg, &lmask, -1, TDQ_LOAD(tdq) - 1, high, 1);
888 /* Stop if we looked well and found no less loaded CPU. */
889 if (anylow && low == -1)
890 break;
891 /* Go to next high if we found no less loaded CPU. */
892 if (low == -1)
893 continue;
894 /* Transfer thread from high to low. */
895 if (sched_balance_pair(tdq, TDQ_CPU(low))) {
896 /* CPU that got thread can no longer be a donor. */
897 CPU_CLR(low, &hmask);
898 } else {
899 /*
900 * If failed, then there is no threads on high
901 * that can run on this low. Drop low from low
902 * mask and look for different one.
903 */
904 CPU_CLR(low, &lmask);
905 anylow = 0;
906 goto nextlow;
907 }
908 }
909 }
910
911 static void
sched_balance(void)912 sched_balance(void)
913 {
914 struct tdq *tdq;
915
916 balance_ticks = max(balance_interval / 2, 1) +
917 (sched_random() % balance_interval);
918 tdq = TDQ_SELF();
919 TDQ_UNLOCK(tdq);
920 sched_balance_group(cpu_top);
921 TDQ_LOCK(tdq);
922 }
923
924 /*
925 * Lock two thread queues using their address to maintain lock order.
926 */
927 static void
tdq_lock_pair(struct tdq * one,struct tdq * two)928 tdq_lock_pair(struct tdq *one, struct tdq *two)
929 {
930 if (one < two) {
931 TDQ_LOCK(one);
932 TDQ_LOCK_FLAGS(two, MTX_DUPOK);
933 } else {
934 TDQ_LOCK(two);
935 TDQ_LOCK_FLAGS(one, MTX_DUPOK);
936 }
937 }
938
939 /*
940 * Unlock two thread queues. Order is not important here.
941 */
942 static void
tdq_unlock_pair(struct tdq * one,struct tdq * two)943 tdq_unlock_pair(struct tdq *one, struct tdq *two)
944 {
945 TDQ_UNLOCK(one);
946 TDQ_UNLOCK(two);
947 }
948
949 /*
950 * Transfer load between two imbalanced thread queues. Returns true if a thread
951 * was moved between the queues, and false otherwise.
952 */
953 static bool
sched_balance_pair(struct tdq * high,struct tdq * low)954 sched_balance_pair(struct tdq *high, struct tdq *low)
955 {
956 int cpu, lowpri;
957 bool ret;
958
959 ret = false;
960 tdq_lock_pair(high, low);
961
962 /*
963 * Transfer a thread from high to low.
964 */
965 if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load) {
966 lowpri = tdq_move(high, low);
967 if (lowpri != -1) {
968 /*
969 * In case the target isn't the current CPU notify it of
970 * the new load, possibly sending an IPI to force it to
971 * reschedule. Otherwise maybe schedule a preemption.
972 */
973 cpu = TDQ_ID(low);
974 if (cpu != PCPU_GET(cpuid))
975 tdq_notify(low, lowpri);
976 else
977 sched_setpreempt(low->tdq_lowpri);
978 ret = true;
979 }
980 }
981 tdq_unlock_pair(high, low);
982 return (ret);
983 }
984
985 /*
986 * Move a thread from one thread queue to another. Returns -1 if the source
987 * queue was empty, else returns the maximum priority of all threads in
988 * the destination queue prior to the addition of the new thread. In the latter
989 * case, this priority can be used to determine whether an IPI needs to be
990 * delivered.
991 */
992 static int
tdq_move(struct tdq * from,struct tdq * to)993 tdq_move(struct tdq *from, struct tdq *to)
994 {
995 struct thread *td;
996 int cpu;
997
998 TDQ_LOCK_ASSERT(from, MA_OWNED);
999 TDQ_LOCK_ASSERT(to, MA_OWNED);
1000
1001 cpu = TDQ_ID(to);
1002 td = tdq_steal(from, cpu);
1003 if (td == NULL)
1004 return (-1);
1005
1006 /*
1007 * Although the run queue is locked the thread may be
1008 * blocked. We can not set the lock until it is unblocked.
1009 */
1010 thread_lock_block_wait(td);
1011 sched_rem(td);
1012 THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(from));
1013 td->td_lock = TDQ_LOCKPTR(to);
1014 td_get_sched(td)->ts_cpu = cpu;
1015 return (tdq_add(to, td, SRQ_YIELDING));
1016 }
1017
1018 /*
1019 * This tdq has idled. Try to steal a thread from another cpu and switch
1020 * to it.
1021 */
1022 static int
tdq_idled(struct tdq * tdq)1023 tdq_idled(struct tdq *tdq)
1024 {
1025 struct cpu_group *cg, *parent;
1026 struct tdq *steal;
1027 cpuset_t mask;
1028 int cpu, switchcnt, goup;
1029
1030 if (smp_started == 0 || steal_idle == 0 || tdq->tdq_cg == NULL)
1031 return (1);
1032 CPU_FILL(&mask);
1033 CPU_CLR(PCPU_GET(cpuid), &mask);
1034 restart:
1035 switchcnt = TDQ_SWITCHCNT(tdq);
1036 for (cg = tdq->tdq_cg, goup = 0; ; ) {
1037 cpu = sched_highest(cg, &mask, steal_thresh, 1);
1038 /*
1039 * We were assigned a thread but not preempted. Returning
1040 * 0 here will cause our caller to switch to it.
1041 */
1042 if (TDQ_LOAD(tdq))
1043 return (0);
1044
1045 /*
1046 * We found no CPU to steal from in this group. Escalate to
1047 * the parent and repeat. But if parent has only two children
1048 * groups we can avoid searching this group again by searching
1049 * the other one specifically and then escalating two levels.
1050 */
1051 if (cpu == -1) {
1052 if (goup) {
1053 cg = cg->cg_parent;
1054 goup = 0;
1055 }
1056 parent = cg->cg_parent;
1057 if (parent == NULL)
1058 return (1);
1059 if (parent->cg_children == 2) {
1060 if (cg == &parent->cg_child[0])
1061 cg = &parent->cg_child[1];
1062 else
1063 cg = &parent->cg_child[0];
1064 goup = 1;
1065 } else
1066 cg = parent;
1067 continue;
1068 }
1069 steal = TDQ_CPU(cpu);
1070 /*
1071 * The data returned by sched_highest() is stale and
1072 * the chosen CPU no longer has an eligible thread.
1073 *
1074 * Testing this ahead of tdq_lock_pair() only catches
1075 * this situation about 20% of the time on an 8 core
1076 * 16 thread Ryzen 7, but it still helps performance.
1077 */
1078 if (TDQ_LOAD(steal) < steal_thresh ||
1079 TDQ_TRANSFERABLE(steal) == 0)
1080 goto restart;
1081 /*
1082 * Try to lock both queues. If we are assigned a thread while
1083 * waited for the lock, switch to it now instead of stealing.
1084 * If we can't get the lock, then somebody likely got there
1085 * first so continue searching.
1086 */
1087 TDQ_LOCK(tdq);
1088 if (tdq->tdq_load > 0) {
1089 mi_switch(SW_VOL | SWT_IDLE);
1090 return (0);
1091 }
1092 if (TDQ_TRYLOCK_FLAGS(steal, MTX_DUPOK) == 0) {
1093 TDQ_UNLOCK(tdq);
1094 CPU_CLR(cpu, &mask);
1095 continue;
1096 }
1097 /*
1098 * The data returned by sched_highest() is stale and
1099 * the chosen CPU no longer has an eligible thread, or
1100 * we were preempted and the CPU loading info may be out
1101 * of date. The latter is rare. In either case restart
1102 * the search.
1103 */
1104 if (TDQ_LOAD(steal) < steal_thresh ||
1105 TDQ_TRANSFERABLE(steal) == 0 ||
1106 switchcnt != TDQ_SWITCHCNT(tdq)) {
1107 tdq_unlock_pair(tdq, steal);
1108 goto restart;
1109 }
1110 /*
1111 * Steal the thread and switch to it.
1112 */
1113 if (tdq_move(steal, tdq) != -1)
1114 break;
1115 /*
1116 * We failed to acquire a thread even though it looked
1117 * like one was available. This could be due to affinity
1118 * restrictions or for other reasons. Loop again after
1119 * removing this CPU from the set. The restart logic
1120 * above does not restore this CPU to the set due to the
1121 * likelyhood of failing here again.
1122 */
1123 CPU_CLR(cpu, &mask);
1124 tdq_unlock_pair(tdq, steal);
1125 }
1126 TDQ_UNLOCK(steal);
1127 mi_switch(SW_VOL | SWT_IDLE);
1128 return (0);
1129 }
1130
1131 /*
1132 * Notify a remote cpu of new work. Sends an IPI if criteria are met.
1133 *
1134 * "lowpri" is the minimum scheduling priority among all threads on
1135 * the queue prior to the addition of the new thread.
1136 */
1137 static void
tdq_notify(struct tdq * tdq,int lowpri)1138 tdq_notify(struct tdq *tdq, int lowpri)
1139 {
1140 int cpu;
1141
1142 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
1143 KASSERT(tdq->tdq_lowpri <= lowpri,
1144 ("tdq_notify: lowpri %d > tdq_lowpri %d", lowpri, tdq->tdq_lowpri));
1145
1146 if (tdq->tdq_owepreempt)
1147 return;
1148
1149 /*
1150 * Check to see if the newly added thread should preempt the one
1151 * currently running.
1152 */
1153 if (!sched_shouldpreempt(tdq->tdq_lowpri, lowpri, 1))
1154 return;
1155
1156 /*
1157 * Make sure that our caller's earlier update to tdq_load is
1158 * globally visible before we read tdq_cpu_idle. Idle thread
1159 * accesses both of them without locks, and the order is important.
1160 */
1161 atomic_thread_fence_seq_cst();
1162
1163 /*
1164 * Try to figure out if we can signal the idle thread instead of sending
1165 * an IPI. This check is racy; at worst, we will deliever an IPI
1166 * unnecessarily.
1167 */
1168 cpu = TDQ_ID(tdq);
1169 if (TD_IS_IDLETHREAD(tdq->tdq_curthread) &&
1170 (atomic_load_int(&tdq->tdq_cpu_idle) == 0 || cpu_idle_wakeup(cpu)))
1171 return;
1172
1173 /*
1174 * The run queues have been updated, so any switch on the remote CPU
1175 * will satisfy the preemption request.
1176 */
1177 tdq->tdq_owepreempt = 1;
1178 ipi_cpu(cpu, IPI_PREEMPT);
1179 }
1180
1181 /*
1182 * Steals load from a timeshare queue. Honors the rotating queue head
1183 * index.
1184 */
1185 static struct thread *
runq_steal_from(struct runq * rq,int cpu,u_char start)1186 runq_steal_from(struct runq *rq, int cpu, u_char start)
1187 {
1188 struct rqbits *rqb;
1189 struct rqhead *rqh;
1190 struct thread *td, *first;
1191 int bit;
1192 int i;
1193
1194 rqb = &rq->rq_status;
1195 bit = start & (RQB_BPW -1);
1196 first = NULL;
1197 again:
1198 for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
1199 if (rqb->rqb_bits[i] == 0)
1200 continue;
1201 if (bit == 0)
1202 bit = RQB_FFS(rqb->rqb_bits[i]);
1203 for (; bit < RQB_BPW; bit++) {
1204 if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
1205 continue;
1206 rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
1207 TAILQ_FOREACH(td, rqh, td_runq) {
1208 if (first) {
1209 if (THREAD_CAN_MIGRATE(td) &&
1210 THREAD_CAN_SCHED(td, cpu))
1211 return (td);
1212 } else
1213 first = td;
1214 }
1215 }
1216 }
1217 if (start != 0) {
1218 start = 0;
1219 goto again;
1220 }
1221
1222 if (first && THREAD_CAN_MIGRATE(first) &&
1223 THREAD_CAN_SCHED(first, cpu))
1224 return (first);
1225 return (NULL);
1226 }
1227
1228 /*
1229 * Steals load from a standard linear queue.
1230 */
1231 static struct thread *
runq_steal(struct runq * rq,int cpu)1232 runq_steal(struct runq *rq, int cpu)
1233 {
1234 struct rqhead *rqh;
1235 struct rqbits *rqb;
1236 struct thread *td;
1237 int word;
1238 int bit;
1239
1240 rqb = &rq->rq_status;
1241 for (word = 0; word < RQB_LEN; word++) {
1242 if (rqb->rqb_bits[word] == 0)
1243 continue;
1244 for (bit = 0; bit < RQB_BPW; bit++) {
1245 if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
1246 continue;
1247 rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
1248 TAILQ_FOREACH(td, rqh, td_runq)
1249 if (THREAD_CAN_MIGRATE(td) &&
1250 THREAD_CAN_SCHED(td, cpu))
1251 return (td);
1252 }
1253 }
1254 return (NULL);
1255 }
1256
1257 /*
1258 * Attempt to steal a thread in priority order from a thread queue.
1259 */
1260 static struct thread *
tdq_steal(struct tdq * tdq,int cpu)1261 tdq_steal(struct tdq *tdq, int cpu)
1262 {
1263 struct thread *td;
1264
1265 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
1266 if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
1267 return (td);
1268 if ((td = runq_steal_from(&tdq->tdq_timeshare,
1269 cpu, tdq->tdq_ridx)) != NULL)
1270 return (td);
1271 return (runq_steal(&tdq->tdq_idle, cpu));
1272 }
1273
1274 /*
1275 * Sets the thread lock and ts_cpu to match the requested cpu. Unlocks the
1276 * current lock and returns with the assigned queue locked.
1277 */
1278 static inline struct tdq *
sched_setcpu(struct thread * td,int cpu,int flags)1279 sched_setcpu(struct thread *td, int cpu, int flags)
1280 {
1281
1282 struct tdq *tdq;
1283 struct mtx *mtx;
1284
1285 THREAD_LOCK_ASSERT(td, MA_OWNED);
1286 tdq = TDQ_CPU(cpu);
1287 td_get_sched(td)->ts_cpu = cpu;
1288 /*
1289 * If the lock matches just return the queue.
1290 */
1291 if (td->td_lock == TDQ_LOCKPTR(tdq)) {
1292 KASSERT((flags & SRQ_HOLD) == 0,
1293 ("sched_setcpu: Invalid lock for SRQ_HOLD"));
1294 return (tdq);
1295 }
1296
1297 /*
1298 * The hard case, migration, we need to block the thread first to
1299 * prevent order reversals with other cpus locks.
1300 */
1301 spinlock_enter();
1302 mtx = thread_lock_block(td);
1303 if ((flags & SRQ_HOLD) == 0)
1304 mtx_unlock_spin(mtx);
1305 TDQ_LOCK(tdq);
1306 thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
1307 spinlock_exit();
1308 return (tdq);
1309 }
1310
1311 SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
1312 SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
1313 SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
1314 SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
1315 SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
1316 SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
1317
1318 static int
sched_pickcpu(struct thread * td,int flags)1319 sched_pickcpu(struct thread *td, int flags)
1320 {
1321 struct cpu_group *cg, *ccg;
1322 struct td_sched *ts;
1323 struct tdq *tdq;
1324 cpuset_t *mask;
1325 int cpu, pri, r, self, intr;
1326
1327 self = PCPU_GET(cpuid);
1328 ts = td_get_sched(td);
1329 KASSERT(!CPU_ABSENT(ts->ts_cpu), ("sched_pickcpu: Start scheduler on "
1330 "absent CPU %d for thread %s.", ts->ts_cpu, td->td_name));
1331 if (smp_started == 0)
1332 return (self);
1333 /*
1334 * Don't migrate a running thread from sched_switch().
1335 */
1336 if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
1337 return (ts->ts_cpu);
1338 /*
1339 * Prefer to run interrupt threads on the processors that generate
1340 * the interrupt.
1341 */
1342 if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
1343 curthread->td_intr_nesting_level) {
1344 tdq = TDQ_SELF();
1345 if (tdq->tdq_lowpri >= PRI_MIN_IDLE) {
1346 SCHED_STAT_INC(pickcpu_idle_affinity);
1347 return (self);
1348 }
1349 ts->ts_cpu = self;
1350 intr = 1;
1351 cg = tdq->tdq_cg;
1352 goto llc;
1353 } else {
1354 intr = 0;
1355 tdq = TDQ_CPU(ts->ts_cpu);
1356 cg = tdq->tdq_cg;
1357 }
1358 /*
1359 * If the thread can run on the last cpu and the affinity has not
1360 * expired and it is idle, run it there.
1361 */
1362 if (THREAD_CAN_SCHED(td, ts->ts_cpu) &&
1363 atomic_load_char(&tdq->tdq_lowpri) >= PRI_MIN_IDLE &&
1364 SCHED_AFFINITY(ts, CG_SHARE_L2)) {
1365 if (cg->cg_flags & CG_FLAG_THREAD) {
1366 /* Check all SMT threads for being idle. */
1367 for (cpu = cg->cg_first; cpu <= cg->cg_last; cpu++) {
1368 pri =
1369 atomic_load_char(&TDQ_CPU(cpu)->tdq_lowpri);
1370 if (CPU_ISSET(cpu, &cg->cg_mask) &&
1371 pri < PRI_MIN_IDLE)
1372 break;
1373 }
1374 if (cpu > cg->cg_last) {
1375 SCHED_STAT_INC(pickcpu_idle_affinity);
1376 return (ts->ts_cpu);
1377 }
1378 } else {
1379 SCHED_STAT_INC(pickcpu_idle_affinity);
1380 return (ts->ts_cpu);
1381 }
1382 }
1383 llc:
1384 /*
1385 * Search for the last level cache CPU group in the tree.
1386 * Skip SMT, identical groups and caches with expired affinity.
1387 * Interrupt threads affinity is explicit and never expires.
1388 */
1389 for (ccg = NULL; cg != NULL; cg = cg->cg_parent) {
1390 if (cg->cg_flags & CG_FLAG_THREAD)
1391 continue;
1392 if (cg->cg_children == 1 || cg->cg_count == 1)
1393 continue;
1394 if (cg->cg_level == CG_SHARE_NONE ||
1395 (!intr && !SCHED_AFFINITY(ts, cg->cg_level)))
1396 continue;
1397 ccg = cg;
1398 }
1399 /* Found LLC shared by all CPUs, so do a global search. */
1400 if (ccg == cpu_top)
1401 ccg = NULL;
1402 cpu = -1;
1403 mask = &td->td_cpuset->cs_mask;
1404 pri = td->td_priority;
1405 r = TD_IS_RUNNING(td);
1406 /*
1407 * Try hard to keep interrupts within found LLC. Search the LLC for
1408 * the least loaded CPU we can run now. For NUMA systems it should
1409 * be within target domain, and it also reduces scheduling overhead.
1410 */
1411 if (ccg != NULL && intr) {
1412 cpu = sched_lowest(ccg, mask, pri, INT_MAX, ts->ts_cpu, r);
1413 if (cpu >= 0)
1414 SCHED_STAT_INC(pickcpu_intrbind);
1415 } else
1416 /* Search the LLC for the least loaded idle CPU we can run now. */
1417 if (ccg != NULL) {
1418 cpu = sched_lowest(ccg, mask, max(pri, PRI_MAX_TIMESHARE),
1419 INT_MAX, ts->ts_cpu, r);
1420 if (cpu >= 0)
1421 SCHED_STAT_INC(pickcpu_affinity);
1422 }
1423 /* Search globally for the least loaded CPU we can run now. */
1424 if (cpu < 0) {
1425 cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu, r);
1426 if (cpu >= 0)
1427 SCHED_STAT_INC(pickcpu_lowest);
1428 }
1429 /* Search globally for the least loaded CPU. */
1430 if (cpu < 0) {
1431 cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu, r);
1432 if (cpu >= 0)
1433 SCHED_STAT_INC(pickcpu_lowest);
1434 }
1435 KASSERT(cpu >= 0, ("sched_pickcpu: Failed to find a cpu."));
1436 KASSERT(!CPU_ABSENT(cpu), ("sched_pickcpu: Picked absent CPU %d.", cpu));
1437 /*
1438 * Compare the lowest loaded cpu to current cpu.
1439 */
1440 tdq = TDQ_CPU(cpu);
1441 if (THREAD_CAN_SCHED(td, self) && TDQ_SELF()->tdq_lowpri > pri &&
1442 atomic_load_char(&tdq->tdq_lowpri) < PRI_MIN_IDLE &&
1443 TDQ_LOAD(TDQ_SELF()) <= TDQ_LOAD(tdq) + 1) {
1444 SCHED_STAT_INC(pickcpu_local);
1445 cpu = self;
1446 }
1447 if (cpu != ts->ts_cpu)
1448 SCHED_STAT_INC(pickcpu_migration);
1449 return (cpu);
1450 }
1451 #endif
1452
1453 /*
1454 * Pick the highest priority task we have and return it.
1455 */
1456 static struct thread *
tdq_choose(struct tdq * tdq)1457 tdq_choose(struct tdq *tdq)
1458 {
1459 struct thread *td;
1460
1461 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
1462 td = runq_choose(&tdq->tdq_realtime);
1463 if (td != NULL)
1464 return (td);
1465 td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
1466 if (td != NULL) {
1467 KASSERT(td->td_priority >= PRI_MIN_BATCH,
1468 ("tdq_choose: Invalid priority on timeshare queue %d",
1469 td->td_priority));
1470 return (td);
1471 }
1472 td = runq_choose(&tdq->tdq_idle);
1473 if (td != NULL) {
1474 KASSERT(td->td_priority >= PRI_MIN_IDLE,
1475 ("tdq_choose: Invalid priority on idle queue %d",
1476 td->td_priority));
1477 return (td);
1478 }
1479
1480 return (NULL);
1481 }
1482
1483 /*
1484 * Initialize a thread queue.
1485 */
1486 static void
tdq_setup(struct tdq * tdq,int id)1487 tdq_setup(struct tdq *tdq, int id)
1488 {
1489
1490 if (bootverbose)
1491 printf("ULE: setup cpu %d\n", id);
1492 runq_init(&tdq->tdq_realtime);
1493 runq_init(&tdq->tdq_timeshare);
1494 runq_init(&tdq->tdq_idle);
1495 tdq->tdq_id = id;
1496 snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
1497 "sched lock %d", (int)TDQ_ID(tdq));
1498 mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock", MTX_SPIN);
1499 #ifdef KTR
1500 snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
1501 "CPU %d load", (int)TDQ_ID(tdq));
1502 #endif
1503 }
1504
1505 #ifdef SMP
1506 static void
sched_setup_smp(void)1507 sched_setup_smp(void)
1508 {
1509 struct tdq *tdq;
1510 int i;
1511
1512 cpu_top = smp_topo();
1513 CPU_FOREACH(i) {
1514 tdq = DPCPU_ID_PTR(i, tdq);
1515 tdq_setup(tdq, i);
1516 tdq->tdq_cg = smp_topo_find(cpu_top, i);
1517 if (tdq->tdq_cg == NULL)
1518 panic("Can't find cpu group for %d\n", i);
1519 DPCPU_ID_SET(i, randomval, i * 69069 + 5);
1520 }
1521 PCPU_SET(sched, DPCPU_PTR(tdq));
1522 balance_tdq = TDQ_SELF();
1523 }
1524 #endif
1525
1526 /*
1527 * Setup the thread queues and initialize the topology based on MD
1528 * information.
1529 */
1530 static void
sched_setup(void * dummy)1531 sched_setup(void *dummy)
1532 {
1533 struct tdq *tdq;
1534
1535 #ifdef SMP
1536 sched_setup_smp();
1537 #else
1538 tdq_setup(TDQ_SELF(), 0);
1539 #endif
1540 tdq = TDQ_SELF();
1541
1542 /* Add thread0's load since it's running. */
1543 TDQ_LOCK(tdq);
1544 thread0.td_lock = TDQ_LOCKPTR(tdq);
1545 tdq_load_add(tdq, &thread0);
1546 tdq->tdq_curthread = &thread0;
1547 tdq->tdq_lowpri = thread0.td_priority;
1548 TDQ_UNLOCK(tdq);
1549 }
1550
1551 /*
1552 * This routine determines time constants after stathz and hz are setup.
1553 */
1554 /* ARGSUSED */
1555 static void
sched_initticks(void * dummy)1556 sched_initticks(void *dummy)
1557 {
1558 int incr;
1559
1560 realstathz = stathz ? stathz : hz;
1561 sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR;
1562 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
1563 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
1564 realstathz);
1565
1566 /*
1567 * tickincr is shifted out by 10 to avoid rounding errors due to
1568 * hz not being evenly divisible by stathz on all platforms.
1569 */
1570 incr = (hz << SCHED_TICK_SHIFT) / realstathz;
1571 /*
1572 * This does not work for values of stathz that are more than
1573 * 1 << SCHED_TICK_SHIFT * hz. In practice this does not happen.
1574 */
1575 if (incr == 0)
1576 incr = 1;
1577 tickincr = incr;
1578 #ifdef SMP
1579 /*
1580 * Set the default balance interval now that we know
1581 * what realstathz is.
1582 */
1583 balance_interval = realstathz;
1584 balance_ticks = balance_interval;
1585 affinity = SCHED_AFFINITY_DEFAULT;
1586 #endif
1587 if (sched_idlespinthresh < 0)
1588 sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz;
1589 }
1590
1591 /*
1592 * This is the core of the interactivity algorithm. Determines a score based
1593 * on past behavior. It is the ratio of sleep time to run time scaled to
1594 * a [0, 100] integer. This is the voluntary sleep time of a process, which
1595 * differs from the cpu usage because it does not account for time spent
1596 * waiting on a run-queue. Would be prettier if we had floating point.
1597 *
1598 * When a thread's sleep time is greater than its run time the
1599 * calculation is:
1600 *
1601 * scaling factor
1602 * interactivity score = ---------------------
1603 * sleep time / run time
1604 *
1605 *
1606 * When a thread's run time is greater than its sleep time the
1607 * calculation is:
1608 *
1609 * scaling factor
1610 * interactivity score = 2 * scaling factor - ---------------------
1611 * run time / sleep time
1612 */
1613 static int
sched_interact_score(struct thread * td)1614 sched_interact_score(struct thread *td)
1615 {
1616 struct td_sched *ts;
1617 int div;
1618
1619 ts = td_get_sched(td);
1620 /*
1621 * The score is only needed if this is likely to be an interactive
1622 * task. Don't go through the expense of computing it if there's
1623 * no chance.
1624 */
1625 if (sched_interact <= SCHED_INTERACT_HALF &&
1626 ts->ts_runtime >= ts->ts_slptime)
1627 return (SCHED_INTERACT_HALF);
1628
1629 if (ts->ts_runtime > ts->ts_slptime) {
1630 div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
1631 return (SCHED_INTERACT_HALF +
1632 (SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
1633 }
1634 if (ts->ts_slptime > ts->ts_runtime) {
1635 div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
1636 return (ts->ts_runtime / div);
1637 }
1638 /* runtime == slptime */
1639 if (ts->ts_runtime)
1640 return (SCHED_INTERACT_HALF);
1641
1642 /*
1643 * This can happen if slptime and runtime are 0.
1644 */
1645 return (0);
1646
1647 }
1648
1649 /*
1650 * Scale the scheduling priority according to the "interactivity" of this
1651 * process.
1652 */
1653 static void
sched_priority(struct thread * td)1654 sched_priority(struct thread *td)
1655 {
1656 u_int pri, score;
1657
1658 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
1659 return;
1660 /*
1661 * If the score is interactive we place the thread in the realtime
1662 * queue with a priority that is less than kernel and interrupt
1663 * priorities. These threads are not subject to nice restrictions.
1664 *
1665 * Scores greater than this are placed on the normal timeshare queue
1666 * where the priority is partially decided by the most recent cpu
1667 * utilization and the rest is decided by nice value.
1668 *
1669 * The nice value of the process has a linear effect on the calculated
1670 * score. Negative nice values make it easier for a thread to be
1671 * considered interactive.
1672 */
1673 score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
1674 if (score < sched_interact) {
1675 pri = PRI_MIN_INTERACT;
1676 pri += (PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) * score /
1677 sched_interact;
1678 KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
1679 ("sched_priority: invalid interactive priority %u score %u",
1680 pri, score));
1681 } else {
1682 pri = SCHED_PRI_MIN;
1683 if (td_get_sched(td)->ts_ticks)
1684 pri += min(SCHED_PRI_TICKS(td_get_sched(td)),
1685 SCHED_PRI_RANGE - 1);
1686 pri += SCHED_PRI_NICE(td->td_proc->p_nice);
1687 KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
1688 ("sched_priority: invalid priority %u: nice %d, "
1689 "ticks %d ftick %d ltick %d tick pri %d",
1690 pri, td->td_proc->p_nice, td_get_sched(td)->ts_ticks,
1691 td_get_sched(td)->ts_ftick, td_get_sched(td)->ts_ltick,
1692 SCHED_PRI_TICKS(td_get_sched(td))));
1693 }
1694 sched_user_prio(td, pri);
1695
1696 return;
1697 }
1698
1699 /*
1700 * This routine enforces a maximum limit on the amount of scheduling history
1701 * kept. It is called after either the slptime or runtime is adjusted. This
1702 * function is ugly due to integer math.
1703 */
1704 static void
sched_interact_update(struct thread * td)1705 sched_interact_update(struct thread *td)
1706 {
1707 struct td_sched *ts;
1708 u_int sum;
1709
1710 ts = td_get_sched(td);
1711 sum = ts->ts_runtime + ts->ts_slptime;
1712 if (sum < SCHED_SLP_RUN_MAX)
1713 return;
1714 /*
1715 * This only happens from two places:
1716 * 1) We have added an unusual amount of run time from fork_exit.
1717 * 2) We have added an unusual amount of sleep time from sched_sleep().
1718 */
1719 if (sum > SCHED_SLP_RUN_MAX * 2) {
1720 if (ts->ts_runtime > ts->ts_slptime) {
1721 ts->ts_runtime = SCHED_SLP_RUN_MAX;
1722 ts->ts_slptime = 1;
1723 } else {
1724 ts->ts_slptime = SCHED_SLP_RUN_MAX;
1725 ts->ts_runtime = 1;
1726 }
1727 return;
1728 }
1729 /*
1730 * If we have exceeded by more than 1/5th then the algorithm below
1731 * will not bring us back into range. Dividing by two here forces
1732 * us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
1733 */
1734 if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
1735 ts->ts_runtime /= 2;
1736 ts->ts_slptime /= 2;
1737 return;
1738 }
1739 ts->ts_runtime = (ts->ts_runtime / 5) * 4;
1740 ts->ts_slptime = (ts->ts_slptime / 5) * 4;
1741 }
1742
1743 /*
1744 * Scale back the interactivity history when a child thread is created. The
1745 * history is inherited from the parent but the thread may behave totally
1746 * differently. For example, a shell spawning a compiler process. We want
1747 * to learn that the compiler is behaving badly very quickly.
1748 */
1749 static void
sched_interact_fork(struct thread * td)1750 sched_interact_fork(struct thread *td)
1751 {
1752 struct td_sched *ts;
1753 int ratio;
1754 int sum;
1755
1756 ts = td_get_sched(td);
1757 sum = ts->ts_runtime + ts->ts_slptime;
1758 if (sum > SCHED_SLP_RUN_FORK) {
1759 ratio = sum / SCHED_SLP_RUN_FORK;
1760 ts->ts_runtime /= ratio;
1761 ts->ts_slptime /= ratio;
1762 }
1763 }
1764
1765 /*
1766 * Called from proc0_init() to setup the scheduler fields.
1767 */
1768 void
schedinit(void)1769 schedinit(void)
1770 {
1771 struct td_sched *ts0;
1772
1773 /*
1774 * Set up the scheduler specific parts of thread0.
1775 */
1776 ts0 = td_get_sched(&thread0);
1777 ts0->ts_ltick = ticks;
1778 ts0->ts_ftick = ticks;
1779 ts0->ts_slice = 0;
1780 ts0->ts_cpu = curcpu; /* set valid CPU number */
1781 }
1782
1783 /*
1784 * schedinit_ap() is needed prior to calling sched_throw(NULL) to ensure that
1785 * the pcpu requirements are met for any calls in the period between curthread
1786 * initialization and sched_throw(). One can safely add threads to the queue
1787 * before sched_throw(), for instance, as long as the thread lock is setup
1788 * correctly.
1789 *
1790 * TDQ_SELF() relies on the below sched pcpu setting; it may be used only
1791 * after schedinit_ap().
1792 */
1793 void
schedinit_ap(void)1794 schedinit_ap(void)
1795 {
1796
1797 #ifdef SMP
1798 PCPU_SET(sched, DPCPU_PTR(tdq));
1799 #endif
1800 PCPU_GET(idlethread)->td_lock = TDQ_LOCKPTR(TDQ_SELF());
1801 }
1802
1803 /*
1804 * This is only somewhat accurate since given many processes of the same
1805 * priority they will switch when their slices run out, which will be
1806 * at most sched_slice stathz ticks.
1807 */
1808 int
sched_rr_interval(void)1809 sched_rr_interval(void)
1810 {
1811
1812 /* Convert sched_slice from stathz to hz. */
1813 return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
1814 }
1815
1816 /*
1817 * Update the percent cpu tracking information when it is requested or
1818 * the total history exceeds the maximum. We keep a sliding history of
1819 * tick counts that slowly decays. This is less precise than the 4BSD
1820 * mechanism since it happens with less regular and frequent events.
1821 */
1822 static void
sched_pctcpu_update(struct td_sched * ts,int run)1823 sched_pctcpu_update(struct td_sched *ts, int run)
1824 {
1825 int t = ticks;
1826
1827 /*
1828 * The signed difference may be negative if the thread hasn't run for
1829 * over half of the ticks rollover period.
1830 */
1831 if ((u_int)(t - ts->ts_ltick) >= SCHED_TICK_TARG) {
1832 ts->ts_ticks = 0;
1833 ts->ts_ftick = t - SCHED_TICK_TARG;
1834 } else if (t - ts->ts_ftick >= SCHED_TICK_MAX) {
1835 ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) *
1836 (ts->ts_ltick - (t - SCHED_TICK_TARG));
1837 ts->ts_ftick = t - SCHED_TICK_TARG;
1838 }
1839 if (run)
1840 ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT;
1841 ts->ts_ltick = t;
1842 }
1843
1844 /*
1845 * Adjust the priority of a thread. Move it to the appropriate run-queue
1846 * if necessary. This is the back-end for several priority related
1847 * functions.
1848 */
1849 static void
sched_thread_priority(struct thread * td,u_char prio)1850 sched_thread_priority(struct thread *td, u_char prio)
1851 {
1852 struct tdq *tdq;
1853 int oldpri;
1854
1855 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
1856 "prio:%d", td->td_priority, "new prio:%d", prio,
1857 KTR_ATTR_LINKED, sched_tdname(curthread));
1858 SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
1859 if (td != curthread && prio < td->td_priority) {
1860 KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
1861 "lend prio", "prio:%d", td->td_priority, "new prio:%d",
1862 prio, KTR_ATTR_LINKED, sched_tdname(td));
1863 SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio,
1864 curthread);
1865 }
1866 THREAD_LOCK_ASSERT(td, MA_OWNED);
1867 if (td->td_priority == prio)
1868 return;
1869 /*
1870 * If the priority has been elevated due to priority
1871 * propagation, we may have to move ourselves to a new
1872 * queue. This could be optimized to not re-add in some
1873 * cases.
1874 */
1875 if (TD_ON_RUNQ(td) && prio < td->td_priority) {
1876 sched_rem(td);
1877 td->td_priority = prio;
1878 sched_add(td, SRQ_BORROWING | SRQ_HOLDTD);
1879 return;
1880 }
1881 /*
1882 * If the thread is currently running we may have to adjust the lowpri
1883 * information so other cpus are aware of our current priority.
1884 */
1885 if (TD_IS_RUNNING(td)) {
1886 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu);
1887 oldpri = td->td_priority;
1888 td->td_priority = prio;
1889 if (prio < tdq->tdq_lowpri)
1890 tdq->tdq_lowpri = prio;
1891 else if (tdq->tdq_lowpri == oldpri)
1892 tdq_setlowpri(tdq, td);
1893 return;
1894 }
1895 td->td_priority = prio;
1896 }
1897
1898 /*
1899 * Update a thread's priority when it is lent another thread's
1900 * priority.
1901 */
1902 void
sched_lend_prio(struct thread * td,u_char prio)1903 sched_lend_prio(struct thread *td, u_char prio)
1904 {
1905
1906 td->td_flags |= TDF_BORROWING;
1907 sched_thread_priority(td, prio);
1908 }
1909
1910 /*
1911 * Restore a thread's priority when priority propagation is
1912 * over. The prio argument is the minimum priority the thread
1913 * needs to have to satisfy other possible priority lending
1914 * requests. If the thread's regular priority is less
1915 * important than prio, the thread will keep a priority boost
1916 * of prio.
1917 */
1918 void
sched_unlend_prio(struct thread * td,u_char prio)1919 sched_unlend_prio(struct thread *td, u_char prio)
1920 {
1921 u_char base_pri;
1922
1923 if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
1924 td->td_base_pri <= PRI_MAX_TIMESHARE)
1925 base_pri = td->td_user_pri;
1926 else
1927 base_pri = td->td_base_pri;
1928 if (prio >= base_pri) {
1929 td->td_flags &= ~TDF_BORROWING;
1930 sched_thread_priority(td, base_pri);
1931 } else
1932 sched_lend_prio(td, prio);
1933 }
1934
1935 /*
1936 * Standard entry for setting the priority to an absolute value.
1937 */
1938 void
sched_prio(struct thread * td,u_char prio)1939 sched_prio(struct thread *td, u_char prio)
1940 {
1941 u_char oldprio;
1942
1943 /* First, update the base priority. */
1944 td->td_base_pri = prio;
1945
1946 /*
1947 * If the thread is borrowing another thread's priority, don't
1948 * ever lower the priority.
1949 */
1950 if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
1951 return;
1952
1953 /* Change the real priority. */
1954 oldprio = td->td_priority;
1955 sched_thread_priority(td, prio);
1956
1957 /*
1958 * If the thread is on a turnstile, then let the turnstile update
1959 * its state.
1960 */
1961 if (TD_ON_LOCK(td) && oldprio != prio)
1962 turnstile_adjust(td, oldprio);
1963 }
1964
1965 /*
1966 * Set the base interrupt thread priority.
1967 */
1968 void
sched_ithread_prio(struct thread * td,u_char prio)1969 sched_ithread_prio(struct thread *td, u_char prio)
1970 {
1971 THREAD_LOCK_ASSERT(td, MA_OWNED);
1972 MPASS(td->td_pri_class == PRI_ITHD);
1973 td->td_base_ithread_pri = prio;
1974 sched_prio(td, prio);
1975 }
1976
1977 /*
1978 * Set the base user priority, does not effect current running priority.
1979 */
1980 void
sched_user_prio(struct thread * td,u_char prio)1981 sched_user_prio(struct thread *td, u_char prio)
1982 {
1983
1984 td->td_base_user_pri = prio;
1985 if (td->td_lend_user_pri <= prio)
1986 return;
1987 td->td_user_pri = prio;
1988 }
1989
1990 void
sched_lend_user_prio(struct thread * td,u_char prio)1991 sched_lend_user_prio(struct thread *td, u_char prio)
1992 {
1993
1994 THREAD_LOCK_ASSERT(td, MA_OWNED);
1995 td->td_lend_user_pri = prio;
1996 td->td_user_pri = min(prio, td->td_base_user_pri);
1997 if (td->td_priority > td->td_user_pri)
1998 sched_prio(td, td->td_user_pri);
1999 else if (td->td_priority != td->td_user_pri)
2000 ast_sched_locked(td, TDA_SCHED);
2001 }
2002
2003 /*
2004 * Like the above but first check if there is anything to do.
2005 */
2006 void
sched_lend_user_prio_cond(struct thread * td,u_char prio)2007 sched_lend_user_prio_cond(struct thread *td, u_char prio)
2008 {
2009
2010 if (td->td_lend_user_pri == prio)
2011 return;
2012
2013 thread_lock(td);
2014 sched_lend_user_prio(td, prio);
2015 thread_unlock(td);
2016 }
2017
2018 #ifdef SMP
2019 /*
2020 * This tdq is about to idle. Try to steal a thread from another CPU before
2021 * choosing the idle thread.
2022 */
2023 static void
tdq_trysteal(struct tdq * tdq)2024 tdq_trysteal(struct tdq *tdq)
2025 {
2026 struct cpu_group *cg, *parent;
2027 struct tdq *steal;
2028 cpuset_t mask;
2029 int cpu, i, goup;
2030
2031 if (smp_started == 0 || steal_idle == 0 || trysteal_limit == 0 ||
2032 tdq->tdq_cg == NULL)
2033 return;
2034 CPU_FILL(&mask);
2035 CPU_CLR(PCPU_GET(cpuid), &mask);
2036 /* We don't want to be preempted while we're iterating. */
2037 spinlock_enter();
2038 TDQ_UNLOCK(tdq);
2039 for (i = 1, cg = tdq->tdq_cg, goup = 0; ; ) {
2040 cpu = sched_highest(cg, &mask, steal_thresh, 1);
2041 /*
2042 * If a thread was added while interrupts were disabled don't
2043 * steal one here.
2044 */
2045 if (TDQ_LOAD(tdq) > 0) {
2046 TDQ_LOCK(tdq);
2047 break;
2048 }
2049
2050 /*
2051 * We found no CPU to steal from in this group. Escalate to
2052 * the parent and repeat. But if parent has only two children
2053 * groups we can avoid searching this group again by searching
2054 * the other one specifically and then escalating two levels.
2055 */
2056 if (cpu == -1) {
2057 if (goup) {
2058 cg = cg->cg_parent;
2059 goup = 0;
2060 }
2061 if (++i > trysteal_limit) {
2062 TDQ_LOCK(tdq);
2063 break;
2064 }
2065 parent = cg->cg_parent;
2066 if (parent == NULL) {
2067 TDQ_LOCK(tdq);
2068 break;
2069 }
2070 if (parent->cg_children == 2) {
2071 if (cg == &parent->cg_child[0])
2072 cg = &parent->cg_child[1];
2073 else
2074 cg = &parent->cg_child[0];
2075 goup = 1;
2076 } else
2077 cg = parent;
2078 continue;
2079 }
2080 steal = TDQ_CPU(cpu);
2081 /*
2082 * The data returned by sched_highest() is stale and
2083 * the chosen CPU no longer has an eligible thread.
2084 * At this point unconditionally exit the loop to bound
2085 * the time spent in the critcal section.
2086 */
2087 if (TDQ_LOAD(steal) < steal_thresh ||
2088 TDQ_TRANSFERABLE(steal) == 0)
2089 continue;
2090 /*
2091 * Try to lock both queues. If we are assigned a thread while
2092 * waited for the lock, switch to it now instead of stealing.
2093 * If we can't get the lock, then somebody likely got there
2094 * first.
2095 */
2096 TDQ_LOCK(tdq);
2097 if (tdq->tdq_load > 0)
2098 break;
2099 if (TDQ_TRYLOCK_FLAGS(steal, MTX_DUPOK) == 0)
2100 break;
2101 /*
2102 * The data returned by sched_highest() is stale and
2103 * the chosen CPU no longer has an eligible thread.
2104 */
2105 if (TDQ_LOAD(steal) < steal_thresh ||
2106 TDQ_TRANSFERABLE(steal) == 0) {
2107 TDQ_UNLOCK(steal);
2108 break;
2109 }
2110 /*
2111 * If we fail to acquire one due to affinity restrictions,
2112 * bail out and let the idle thread to a more complete search
2113 * outside of a critical section.
2114 */
2115 if (tdq_move(steal, tdq) == -1) {
2116 TDQ_UNLOCK(steal);
2117 break;
2118 }
2119 TDQ_UNLOCK(steal);
2120 break;
2121 }
2122 spinlock_exit();
2123 }
2124 #endif
2125
2126 /*
2127 * Handle migration from sched_switch(). This happens only for
2128 * cpu binding.
2129 */
2130 static struct mtx *
sched_switch_migrate(struct tdq * tdq,struct thread * td,int flags)2131 sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
2132 {
2133 struct tdq *tdn;
2134 #ifdef SMP
2135 int lowpri;
2136 #endif
2137
2138 KASSERT(THREAD_CAN_MIGRATE(td) ||
2139 (td_get_sched(td)->ts_flags & TSF_BOUND) != 0,
2140 ("Thread %p shouldn't migrate", td));
2141 KASSERT(!CPU_ABSENT(td_get_sched(td)->ts_cpu), ("sched_switch_migrate: "
2142 "thread %s queued on absent CPU %d.", td->td_name,
2143 td_get_sched(td)->ts_cpu));
2144 tdn = TDQ_CPU(td_get_sched(td)->ts_cpu);
2145 #ifdef SMP
2146 tdq_load_rem(tdq, td);
2147 /*
2148 * Do the lock dance required to avoid LOR. We have an
2149 * extra spinlock nesting from sched_switch() which will
2150 * prevent preemption while we're holding neither run-queue lock.
2151 */
2152 TDQ_UNLOCK(tdq);
2153 TDQ_LOCK(tdn);
2154 lowpri = tdq_add(tdn, td, flags);
2155 tdq_notify(tdn, lowpri);
2156 TDQ_UNLOCK(tdn);
2157 TDQ_LOCK(tdq);
2158 #endif
2159 return (TDQ_LOCKPTR(tdn));
2160 }
2161
2162 /*
2163 * thread_lock_unblock() that does not assume td_lock is blocked.
2164 */
2165 static inline void
thread_unblock_switch(struct thread * td,struct mtx * mtx)2166 thread_unblock_switch(struct thread *td, struct mtx *mtx)
2167 {
2168 atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
2169 (uintptr_t)mtx);
2170 }
2171
2172 /*
2173 * Switch threads. This function has to handle threads coming in while
2174 * blocked for some reason, running, or idle. It also must deal with
2175 * migrating a thread from one queue to another as running threads may
2176 * be assigned elsewhere via binding.
2177 */
2178 void
sched_switch(struct thread * td,int flags)2179 sched_switch(struct thread *td, int flags)
2180 {
2181 struct thread *newtd;
2182 struct tdq *tdq;
2183 struct td_sched *ts;
2184 struct mtx *mtx;
2185 int srqflag;
2186 int cpuid, preempted;
2187 #ifdef SMP
2188 int pickcpu;
2189 #endif
2190
2191 THREAD_LOCK_ASSERT(td, MA_OWNED);
2192
2193 cpuid = PCPU_GET(cpuid);
2194 tdq = TDQ_SELF();
2195 ts = td_get_sched(td);
2196 sched_pctcpu_update(ts, 1);
2197 #ifdef SMP
2198 pickcpu = (td->td_flags & TDF_PICKCPU) != 0;
2199 if (pickcpu)
2200 ts->ts_rltick = ticks - affinity * MAX_CACHE_LEVELS;
2201 else
2202 ts->ts_rltick = ticks;
2203 #endif
2204 td->td_lastcpu = td->td_oncpu;
2205 preempted = (td->td_flags & TDF_SLICEEND) == 0 &&
2206 (flags & SW_PREEMPT) != 0;
2207 td->td_flags &= ~(TDF_PICKCPU | TDF_SLICEEND);
2208 ast_unsched_locked(td, TDA_SCHED);
2209 td->td_owepreempt = 0;
2210 atomic_store_char(&tdq->tdq_owepreempt, 0);
2211 if (!TD_IS_IDLETHREAD(td))
2212 TDQ_SWITCHCNT_INC(tdq);
2213
2214 /*
2215 * Always block the thread lock so we can drop the tdq lock early.
2216 */
2217 mtx = thread_lock_block(td);
2218 spinlock_enter();
2219 if (TD_IS_IDLETHREAD(td)) {
2220 MPASS(mtx == TDQ_LOCKPTR(tdq));
2221 TD_SET_CAN_RUN(td);
2222 } else if (TD_IS_RUNNING(td)) {
2223 MPASS(mtx == TDQ_LOCKPTR(tdq));
2224 srqflag = SRQ_OURSELF | SRQ_YIELDING |
2225 (preempted ? SRQ_PREEMPTED : 0);
2226 #ifdef SMP
2227 if (THREAD_CAN_MIGRATE(td) && (!THREAD_CAN_SCHED(td, ts->ts_cpu)
2228 || pickcpu))
2229 ts->ts_cpu = sched_pickcpu(td, 0);
2230 #endif
2231 if (ts->ts_cpu == cpuid)
2232 tdq_runq_add(tdq, td, srqflag);
2233 else
2234 mtx = sched_switch_migrate(tdq, td, srqflag);
2235 } else {
2236 /* This thread must be going to sleep. */
2237 if (mtx != TDQ_LOCKPTR(tdq)) {
2238 mtx_unlock_spin(mtx);
2239 TDQ_LOCK(tdq);
2240 }
2241 tdq_load_rem(tdq, td);
2242 #ifdef SMP
2243 if (tdq->tdq_load == 0)
2244 tdq_trysteal(tdq);
2245 #endif
2246 }
2247
2248 #if (KTR_COMPILE & KTR_SCHED) != 0
2249 if (TD_IS_IDLETHREAD(td))
2250 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
2251 "prio:%d", td->td_priority);
2252 else
2253 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
2254 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
2255 "lockname:\"%s\"", td->td_lockname);
2256 #endif
2257
2258 /*
2259 * We enter here with the thread blocked and assigned to the
2260 * appropriate cpu run-queue or sleep-queue and with the current
2261 * thread-queue locked.
2262 */
2263 TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
2264 MPASS(td == tdq->tdq_curthread);
2265 newtd = choosethread();
2266 sched_pctcpu_update(td_get_sched(newtd), 0);
2267 TDQ_UNLOCK(tdq);
2268
2269 /*
2270 * Call the MD code to switch contexts if necessary.
2271 */
2272 if (td != newtd) {
2273 #ifdef HWPMC_HOOKS
2274 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
2275 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
2276 #endif
2277 SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
2278
2279 #ifdef KDTRACE_HOOKS
2280 /*
2281 * If DTrace has set the active vtime enum to anything
2282 * other than INACTIVE (0), then it should have set the
2283 * function to call.
2284 */
2285 if (dtrace_vtime_active)
2286 (*dtrace_vtime_switch_func)(newtd);
2287 #endif
2288 td->td_oncpu = NOCPU;
2289 cpu_switch(td, newtd, mtx);
2290 cpuid = td->td_oncpu = PCPU_GET(cpuid);
2291
2292 SDT_PROBE0(sched, , , on__cpu);
2293 #ifdef HWPMC_HOOKS
2294 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
2295 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
2296 #endif
2297 } else {
2298 thread_unblock_switch(td, mtx);
2299 SDT_PROBE0(sched, , , remain__cpu);
2300 }
2301 KASSERT(curthread->td_md.md_spinlock_count == 1,
2302 ("invalid count %d", curthread->td_md.md_spinlock_count));
2303
2304 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
2305 "prio:%d", td->td_priority);
2306 }
2307
2308 /*
2309 * Adjust thread priorities as a result of a nice request.
2310 */
2311 void
sched_nice(struct proc * p,int nice)2312 sched_nice(struct proc *p, int nice)
2313 {
2314 struct thread *td;
2315
2316 PROC_LOCK_ASSERT(p, MA_OWNED);
2317
2318 p->p_nice = nice;
2319 FOREACH_THREAD_IN_PROC(p, td) {
2320 thread_lock(td);
2321 sched_priority(td);
2322 sched_prio(td, td->td_base_user_pri);
2323 thread_unlock(td);
2324 }
2325 }
2326
2327 /*
2328 * Record the sleep time for the interactivity scorer.
2329 */
2330 void
sched_sleep(struct thread * td,int prio)2331 sched_sleep(struct thread *td, int prio)
2332 {
2333
2334 THREAD_LOCK_ASSERT(td, MA_OWNED);
2335
2336 td->td_slptick = ticks;
2337 if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
2338 return;
2339 if (static_boost == 1 && prio)
2340 sched_prio(td, prio);
2341 else if (static_boost && td->td_priority > static_boost)
2342 sched_prio(td, static_boost);
2343 }
2344
2345 /*
2346 * Schedule a thread to resume execution and record how long it voluntarily
2347 * slept. We also update the pctcpu, interactivity, and priority.
2348 *
2349 * Requires the thread lock on entry, drops on exit.
2350 */
2351 void
sched_wakeup(struct thread * td,int srqflags)2352 sched_wakeup(struct thread *td, int srqflags)
2353 {
2354 struct td_sched *ts;
2355 int slptick;
2356
2357 THREAD_LOCK_ASSERT(td, MA_OWNED);
2358 ts = td_get_sched(td);
2359
2360 /*
2361 * If we slept for more than a tick update our interactivity and
2362 * priority.
2363 */
2364 slptick = td->td_slptick;
2365 td->td_slptick = 0;
2366 if (slptick && slptick != ticks) {
2367 ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT;
2368 sched_interact_update(td);
2369 sched_pctcpu_update(ts, 0);
2370 }
2371
2372 /*
2373 * When resuming an idle ithread, restore its base ithread
2374 * priority.
2375 */
2376 if (PRI_BASE(td->td_pri_class) == PRI_ITHD &&
2377 td->td_priority != td->td_base_ithread_pri)
2378 sched_prio(td, td->td_base_ithread_pri);
2379
2380 /*
2381 * Reset the slice value since we slept and advanced the round-robin.
2382 */
2383 ts->ts_slice = 0;
2384 sched_add(td, SRQ_BORING | srqflags);
2385 }
2386
2387 /*
2388 * Penalize the parent for creating a new child and initialize the child's
2389 * priority.
2390 */
2391 void
sched_fork(struct thread * td,struct thread * child)2392 sched_fork(struct thread *td, struct thread *child)
2393 {
2394 THREAD_LOCK_ASSERT(td, MA_OWNED);
2395 sched_pctcpu_update(td_get_sched(td), 1);
2396 sched_fork_thread(td, child);
2397 /*
2398 * Penalize the parent and child for forking.
2399 */
2400 sched_interact_fork(child);
2401 sched_priority(child);
2402 td_get_sched(td)->ts_runtime += tickincr;
2403 sched_interact_update(td);
2404 sched_priority(td);
2405 }
2406
2407 /*
2408 * Fork a new thread, may be within the same process.
2409 */
2410 void
sched_fork_thread(struct thread * td,struct thread * child)2411 sched_fork_thread(struct thread *td, struct thread *child)
2412 {
2413 struct td_sched *ts;
2414 struct td_sched *ts2;
2415 struct tdq *tdq;
2416
2417 tdq = TDQ_SELF();
2418 THREAD_LOCK_ASSERT(td, MA_OWNED);
2419 /*
2420 * Initialize child.
2421 */
2422 ts = td_get_sched(td);
2423 ts2 = td_get_sched(child);
2424 child->td_oncpu = NOCPU;
2425 child->td_lastcpu = NOCPU;
2426 child->td_lock = TDQ_LOCKPTR(tdq);
2427 child->td_cpuset = cpuset_ref(td->td_cpuset);
2428 child->td_domain.dr_policy = td->td_cpuset->cs_domain;
2429 ts2->ts_cpu = ts->ts_cpu;
2430 ts2->ts_flags = 0;
2431 /*
2432 * Grab our parents cpu estimation information.
2433 */
2434 ts2->ts_ticks = ts->ts_ticks;
2435 ts2->ts_ltick = ts->ts_ltick;
2436 ts2->ts_ftick = ts->ts_ftick;
2437 /*
2438 * Do not inherit any borrowed priority from the parent.
2439 */
2440 child->td_priority = child->td_base_pri;
2441 /*
2442 * And update interactivity score.
2443 */
2444 ts2->ts_slptime = ts->ts_slptime;
2445 ts2->ts_runtime = ts->ts_runtime;
2446 /* Attempt to quickly learn interactivity. */
2447 ts2->ts_slice = tdq_slice(tdq) - sched_slice_min;
2448 #ifdef KTR
2449 bzero(ts2->ts_name, sizeof(ts2->ts_name));
2450 #endif
2451 }
2452
2453 /*
2454 * Adjust the priority class of a thread.
2455 */
2456 void
sched_class(struct thread * td,int class)2457 sched_class(struct thread *td, int class)
2458 {
2459
2460 THREAD_LOCK_ASSERT(td, MA_OWNED);
2461 if (td->td_pri_class == class)
2462 return;
2463 td->td_pri_class = class;
2464 }
2465
2466 /*
2467 * Return some of the child's priority and interactivity to the parent.
2468 */
2469 void
sched_exit(struct proc * p,struct thread * child)2470 sched_exit(struct proc *p, struct thread *child)
2471 {
2472 struct thread *td;
2473
2474 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
2475 "prio:%d", child->td_priority);
2476 PROC_LOCK_ASSERT(p, MA_OWNED);
2477 td = FIRST_THREAD_IN_PROC(p);
2478 sched_exit_thread(td, child);
2479 }
2480
2481 /*
2482 * Penalize another thread for the time spent on this one. This helps to
2483 * worsen the priority and interactivity of processes which schedule batch
2484 * jobs such as make. This has little effect on the make process itself but
2485 * causes new processes spawned by it to receive worse scores immediately.
2486 */
2487 void
sched_exit_thread(struct thread * td,struct thread * child)2488 sched_exit_thread(struct thread *td, struct thread *child)
2489 {
2490
2491 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
2492 "prio:%d", child->td_priority);
2493 /*
2494 * Give the child's runtime to the parent without returning the
2495 * sleep time as a penalty to the parent. This causes shells that
2496 * launch expensive things to mark their children as expensive.
2497 */
2498 thread_lock(td);
2499 td_get_sched(td)->ts_runtime += td_get_sched(child)->ts_runtime;
2500 sched_interact_update(td);
2501 sched_priority(td);
2502 thread_unlock(td);
2503 }
2504
2505 void
sched_preempt(struct thread * td)2506 sched_preempt(struct thread *td)
2507 {
2508 struct tdq *tdq;
2509 int flags;
2510
2511 SDT_PROBE2(sched, , , surrender, td, td->td_proc);
2512
2513 thread_lock(td);
2514 tdq = TDQ_SELF();
2515 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2516 if (td->td_priority > tdq->tdq_lowpri) {
2517 if (td->td_critnest == 1) {
2518 flags = SW_INVOL | SW_PREEMPT;
2519 flags |= TD_IS_IDLETHREAD(td) ? SWT_REMOTEWAKEIDLE :
2520 SWT_REMOTEPREEMPT;
2521 mi_switch(flags);
2522 /* Switch dropped thread lock. */
2523 return;
2524 }
2525 td->td_owepreempt = 1;
2526 } else {
2527 tdq->tdq_owepreempt = 0;
2528 }
2529 thread_unlock(td);
2530 }
2531
2532 /*
2533 * Fix priorities on return to user-space. Priorities may be elevated due
2534 * to static priorities in msleep() or similar.
2535 */
2536 void
sched_userret_slowpath(struct thread * td)2537 sched_userret_slowpath(struct thread *td)
2538 {
2539
2540 thread_lock(td);
2541 td->td_priority = td->td_user_pri;
2542 td->td_base_pri = td->td_user_pri;
2543 tdq_setlowpri(TDQ_SELF(), td);
2544 thread_unlock(td);
2545 }
2546
2547 SCHED_STAT_DEFINE(ithread_demotions, "Interrupt thread priority demotions");
2548 SCHED_STAT_DEFINE(ithread_preemptions,
2549 "Interrupt thread preemptions due to time-sharing");
2550
2551 /*
2552 * Return time slice for a given thread. For ithreads this is
2553 * sched_slice. For other threads it is tdq_slice(tdq).
2554 */
2555 static inline int
td_slice(struct thread * td,struct tdq * tdq)2556 td_slice(struct thread *td, struct tdq *tdq)
2557 {
2558 if (PRI_BASE(td->td_pri_class) == PRI_ITHD)
2559 return (sched_slice);
2560 return (tdq_slice(tdq));
2561 }
2562
2563 /*
2564 * Handle a stathz tick. This is really only relevant for timeshare
2565 * and interrupt threads.
2566 */
2567 void
sched_clock(struct thread * td,int cnt)2568 sched_clock(struct thread *td, int cnt)
2569 {
2570 struct tdq *tdq;
2571 struct td_sched *ts;
2572
2573 THREAD_LOCK_ASSERT(td, MA_OWNED);
2574 tdq = TDQ_SELF();
2575 #ifdef SMP
2576 /*
2577 * We run the long term load balancer infrequently on the first cpu.
2578 */
2579 if (balance_tdq == tdq && smp_started != 0 && rebalance != 0 &&
2580 balance_ticks != 0) {
2581 balance_ticks -= cnt;
2582 if (balance_ticks <= 0)
2583 sched_balance();
2584 }
2585 #endif
2586 /*
2587 * Save the old switch count so we have a record of the last ticks
2588 * activity. Initialize the new switch count based on our load.
2589 * If there is some activity seed it to reflect that.
2590 */
2591 tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
2592 tdq->tdq_switchcnt = tdq->tdq_load;
2593
2594 /*
2595 * Advance the insert index once for each tick to ensure that all
2596 * threads get a chance to run.
2597 */
2598 if (tdq->tdq_idx == tdq->tdq_ridx) {
2599 tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
2600 if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
2601 tdq->tdq_ridx = tdq->tdq_idx;
2602 }
2603 ts = td_get_sched(td);
2604 sched_pctcpu_update(ts, 1);
2605 if ((td->td_pri_class & PRI_FIFO_BIT) || TD_IS_IDLETHREAD(td))
2606 return;
2607
2608 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
2609 /*
2610 * We used a tick; charge it to the thread so
2611 * that we can compute our interactivity.
2612 */
2613 td_get_sched(td)->ts_runtime += tickincr * cnt;
2614 sched_interact_update(td);
2615 sched_priority(td);
2616 }
2617
2618 /*
2619 * Force a context switch if the current thread has used up a full
2620 * time slice (default is 100ms).
2621 */
2622 ts->ts_slice += cnt;
2623 if (ts->ts_slice >= td_slice(td, tdq)) {
2624 ts->ts_slice = 0;
2625
2626 /*
2627 * If an ithread uses a full quantum, demote its
2628 * priority and preempt it.
2629 */
2630 if (PRI_BASE(td->td_pri_class) == PRI_ITHD) {
2631 SCHED_STAT_INC(ithread_preemptions);
2632 td->td_owepreempt = 1;
2633 if (td->td_base_pri + RQ_PPQ < PRI_MAX_ITHD) {
2634 SCHED_STAT_INC(ithread_demotions);
2635 sched_prio(td, td->td_base_pri + RQ_PPQ);
2636 }
2637 } else {
2638 ast_sched_locked(td, TDA_SCHED);
2639 td->td_flags |= TDF_SLICEEND;
2640 }
2641 }
2642 }
2643
2644 u_int
sched_estcpu(struct thread * td __unused)2645 sched_estcpu(struct thread *td __unused)
2646 {
2647
2648 return (0);
2649 }
2650
2651 /*
2652 * Return whether the current CPU has runnable tasks. Used for in-kernel
2653 * cooperative idle threads.
2654 */
2655 int
sched_runnable(void)2656 sched_runnable(void)
2657 {
2658 struct tdq *tdq;
2659 int load;
2660
2661 load = 1;
2662
2663 tdq = TDQ_SELF();
2664 if ((curthread->td_flags & TDF_IDLETD) != 0) {
2665 if (TDQ_LOAD(tdq) > 0)
2666 goto out;
2667 } else
2668 if (TDQ_LOAD(tdq) - 1 > 0)
2669 goto out;
2670 load = 0;
2671 out:
2672 return (load);
2673 }
2674
2675 /*
2676 * Choose the highest priority thread to run. The thread is removed from
2677 * the run-queue while running however the load remains.
2678 */
2679 struct thread *
sched_choose(void)2680 sched_choose(void)
2681 {
2682 struct thread *td;
2683 struct tdq *tdq;
2684
2685 tdq = TDQ_SELF();
2686 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2687 td = tdq_choose(tdq);
2688 if (td != NULL) {
2689 tdq_runq_rem(tdq, td);
2690 tdq->tdq_lowpri = td->td_priority;
2691 } else {
2692 tdq->tdq_lowpri = PRI_MAX_IDLE;
2693 td = PCPU_GET(idlethread);
2694 }
2695 tdq->tdq_curthread = td;
2696 return (td);
2697 }
2698
2699 /*
2700 * Set owepreempt if the currently running thread has lower priority than "pri".
2701 * Preemption never happens directly in ULE, we always request it once we exit a
2702 * critical section.
2703 */
2704 static void
sched_setpreempt(int pri)2705 sched_setpreempt(int pri)
2706 {
2707 struct thread *ctd;
2708 int cpri;
2709
2710 ctd = curthread;
2711 THREAD_LOCK_ASSERT(ctd, MA_OWNED);
2712
2713 cpri = ctd->td_priority;
2714 if (pri < cpri)
2715 ast_sched_locked(ctd, TDA_SCHED);
2716 if (KERNEL_PANICKED() || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
2717 return;
2718 if (!sched_shouldpreempt(pri, cpri, 0))
2719 return;
2720 ctd->td_owepreempt = 1;
2721 }
2722
2723 /*
2724 * Add a thread to a thread queue. Select the appropriate runq and add the
2725 * thread to it. This is the internal function called when the tdq is
2726 * predetermined.
2727 */
2728 static int
tdq_add(struct tdq * tdq,struct thread * td,int flags)2729 tdq_add(struct tdq *tdq, struct thread *td, int flags)
2730 {
2731 int lowpri;
2732
2733 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2734 THREAD_LOCK_BLOCKED_ASSERT(td, MA_OWNED);
2735 KASSERT((td->td_inhibitors == 0),
2736 ("sched_add: trying to run inhibited thread"));
2737 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
2738 ("sched_add: bad thread state"));
2739 KASSERT(td->td_flags & TDF_INMEM,
2740 ("sched_add: thread swapped out"));
2741
2742 lowpri = tdq->tdq_lowpri;
2743 if (td->td_priority < lowpri)
2744 tdq->tdq_lowpri = td->td_priority;
2745 tdq_runq_add(tdq, td, flags);
2746 tdq_load_add(tdq, td);
2747 return (lowpri);
2748 }
2749
2750 /*
2751 * Select the target thread queue and add a thread to it. Request
2752 * preemption or IPI a remote processor if required.
2753 *
2754 * Requires the thread lock on entry, drops on exit.
2755 */
2756 void
sched_add(struct thread * td,int flags)2757 sched_add(struct thread *td, int flags)
2758 {
2759 struct tdq *tdq;
2760 #ifdef SMP
2761 int cpu, lowpri;
2762 #endif
2763
2764 KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
2765 "prio:%d", td->td_priority, KTR_ATTR_LINKED,
2766 sched_tdname(curthread));
2767 KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
2768 KTR_ATTR_LINKED, sched_tdname(td));
2769 SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
2770 flags & SRQ_PREEMPTED);
2771 THREAD_LOCK_ASSERT(td, MA_OWNED);
2772 /*
2773 * Recalculate the priority before we select the target cpu or
2774 * run-queue.
2775 */
2776 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
2777 sched_priority(td);
2778 #ifdef SMP
2779 /*
2780 * Pick the destination cpu and if it isn't ours transfer to the
2781 * target cpu.
2782 */
2783 cpu = sched_pickcpu(td, flags);
2784 tdq = sched_setcpu(td, cpu, flags);
2785 lowpri = tdq_add(tdq, td, flags);
2786 if (cpu != PCPU_GET(cpuid))
2787 tdq_notify(tdq, lowpri);
2788 else if (!(flags & SRQ_YIELDING))
2789 sched_setpreempt(td->td_priority);
2790 #else
2791 tdq = TDQ_SELF();
2792 /*
2793 * Now that the thread is moving to the run-queue, set the lock
2794 * to the scheduler's lock.
2795 */
2796 if (td->td_lock != TDQ_LOCKPTR(tdq)) {
2797 TDQ_LOCK(tdq);
2798 if ((flags & SRQ_HOLD) != 0)
2799 td->td_lock = TDQ_LOCKPTR(tdq);
2800 else
2801 thread_lock_set(td, TDQ_LOCKPTR(tdq));
2802 }
2803 (void)tdq_add(tdq, td, flags);
2804 if (!(flags & SRQ_YIELDING))
2805 sched_setpreempt(td->td_priority);
2806 #endif
2807 if (!(flags & SRQ_HOLDTD))
2808 thread_unlock(td);
2809 }
2810
2811 /*
2812 * Remove a thread from a run-queue without running it. This is used
2813 * when we're stealing a thread from a remote queue. Otherwise all threads
2814 * exit by calling sched_exit_thread() and sched_throw() themselves.
2815 */
2816 void
sched_rem(struct thread * td)2817 sched_rem(struct thread *td)
2818 {
2819 struct tdq *tdq;
2820
2821 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
2822 "prio:%d", td->td_priority);
2823 SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
2824 tdq = TDQ_CPU(td_get_sched(td)->ts_cpu);
2825 TDQ_LOCK_ASSERT(tdq, MA_OWNED);
2826 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
2827 KASSERT(TD_ON_RUNQ(td),
2828 ("sched_rem: thread not on run queue"));
2829 tdq_runq_rem(tdq, td);
2830 tdq_load_rem(tdq, td);
2831 TD_SET_CAN_RUN(td);
2832 if (td->td_priority == tdq->tdq_lowpri)
2833 tdq_setlowpri(tdq, NULL);
2834 }
2835
2836 /*
2837 * Fetch cpu utilization information. Updates on demand.
2838 */
2839 fixpt_t
sched_pctcpu(struct thread * td)2840 sched_pctcpu(struct thread *td)
2841 {
2842 fixpt_t pctcpu;
2843 struct td_sched *ts;
2844
2845 pctcpu = 0;
2846 ts = td_get_sched(td);
2847
2848 THREAD_LOCK_ASSERT(td, MA_OWNED);
2849 sched_pctcpu_update(ts, TD_IS_RUNNING(td));
2850 if (ts->ts_ticks) {
2851 int rtick;
2852
2853 /* How many rtick per second ? */
2854 rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
2855 pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
2856 }
2857
2858 return (pctcpu);
2859 }
2860
2861 /*
2862 * Enforce affinity settings for a thread. Called after adjustments to
2863 * cpumask.
2864 */
2865 void
sched_affinity(struct thread * td)2866 sched_affinity(struct thread *td)
2867 {
2868 #ifdef SMP
2869 struct td_sched *ts;
2870
2871 THREAD_LOCK_ASSERT(td, MA_OWNED);
2872 ts = td_get_sched(td);
2873 if (THREAD_CAN_SCHED(td, ts->ts_cpu))
2874 return;
2875 if (TD_ON_RUNQ(td)) {
2876 sched_rem(td);
2877 sched_add(td, SRQ_BORING | SRQ_HOLDTD);
2878 return;
2879 }
2880 if (!TD_IS_RUNNING(td))
2881 return;
2882 /*
2883 * Force a switch before returning to userspace. If the
2884 * target thread is not running locally send an ipi to force
2885 * the issue.
2886 */
2887 ast_sched_locked(td, TDA_SCHED);
2888 if (td != curthread)
2889 ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
2890 #endif
2891 }
2892
2893 /*
2894 * Bind a thread to a target cpu.
2895 */
2896 void
sched_bind(struct thread * td,int cpu)2897 sched_bind(struct thread *td, int cpu)
2898 {
2899 struct td_sched *ts;
2900
2901 THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
2902 KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
2903 ts = td_get_sched(td);
2904 if (ts->ts_flags & TSF_BOUND)
2905 sched_unbind(td);
2906 KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
2907 ts->ts_flags |= TSF_BOUND;
2908 sched_pin();
2909 if (PCPU_GET(cpuid) == cpu)
2910 return;
2911 ts->ts_cpu = cpu;
2912 /* When we return from mi_switch we'll be on the correct cpu. */
2913 mi_switch(SW_VOL | SWT_BIND);
2914 thread_lock(td);
2915 }
2916
2917 /*
2918 * Release a bound thread.
2919 */
2920 void
sched_unbind(struct thread * td)2921 sched_unbind(struct thread *td)
2922 {
2923 struct td_sched *ts;
2924
2925 THREAD_LOCK_ASSERT(td, MA_OWNED);
2926 KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
2927 ts = td_get_sched(td);
2928 if ((ts->ts_flags & TSF_BOUND) == 0)
2929 return;
2930 ts->ts_flags &= ~TSF_BOUND;
2931 sched_unpin();
2932 }
2933
2934 int
sched_is_bound(struct thread * td)2935 sched_is_bound(struct thread *td)
2936 {
2937 THREAD_LOCK_ASSERT(td, MA_OWNED);
2938 return (td_get_sched(td)->ts_flags & TSF_BOUND);
2939 }
2940
2941 /*
2942 * Basic yield call.
2943 */
2944 void
sched_relinquish(struct thread * td)2945 sched_relinquish(struct thread *td)
2946 {
2947 thread_lock(td);
2948 mi_switch(SW_VOL | SWT_RELINQUISH);
2949 }
2950
2951 /*
2952 * Return the total system load.
2953 */
2954 int
sched_load(void)2955 sched_load(void)
2956 {
2957 #ifdef SMP
2958 int total;
2959 int i;
2960
2961 total = 0;
2962 CPU_FOREACH(i)
2963 total += atomic_load_int(&TDQ_CPU(i)->tdq_sysload);
2964 return (total);
2965 #else
2966 return (atomic_load_int(&TDQ_SELF()->tdq_sysload));
2967 #endif
2968 }
2969
2970 int
sched_sizeof_proc(void)2971 sched_sizeof_proc(void)
2972 {
2973 return (sizeof(struct proc));
2974 }
2975
2976 int
sched_sizeof_thread(void)2977 sched_sizeof_thread(void)
2978 {
2979 return (sizeof(struct thread) + sizeof(struct td_sched));
2980 }
2981
2982 #ifdef SMP
2983 #define TDQ_IDLESPIN(tdq) \
2984 ((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
2985 #else
2986 #define TDQ_IDLESPIN(tdq) 1
2987 #endif
2988
2989 /*
2990 * The actual idle process.
2991 */
2992 void
sched_idletd(void * dummy)2993 sched_idletd(void *dummy)
2994 {
2995 struct thread *td;
2996 struct tdq *tdq;
2997 int oldswitchcnt, switchcnt;
2998 int i;
2999
3000 mtx_assert(&Giant, MA_NOTOWNED);
3001 td = curthread;
3002 tdq = TDQ_SELF();
3003 THREAD_NO_SLEEPING();
3004 oldswitchcnt = -1;
3005 for (;;) {
3006 if (TDQ_LOAD(tdq)) {
3007 thread_lock(td);
3008 mi_switch(SW_VOL | SWT_IDLE);
3009 }
3010 switchcnt = TDQ_SWITCHCNT(tdq);
3011 #ifdef SMP
3012 if (always_steal || switchcnt != oldswitchcnt) {
3013 oldswitchcnt = switchcnt;
3014 if (tdq_idled(tdq) == 0)
3015 continue;
3016 }
3017 switchcnt = TDQ_SWITCHCNT(tdq);
3018 #else
3019 oldswitchcnt = switchcnt;
3020 #endif
3021 /*
3022 * If we're switching very frequently, spin while checking
3023 * for load rather than entering a low power state that
3024 * may require an IPI. However, don't do any busy
3025 * loops while on SMT machines as this simply steals
3026 * cycles from cores doing useful work.
3027 */
3028 if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
3029 for (i = 0; i < sched_idlespins; i++) {
3030 if (TDQ_LOAD(tdq))
3031 break;
3032 cpu_spinwait();
3033 }
3034 }
3035
3036 /* If there was context switch during spin, restart it. */
3037 switchcnt = TDQ_SWITCHCNT(tdq);
3038 if (TDQ_LOAD(tdq) != 0 || switchcnt != oldswitchcnt)
3039 continue;
3040
3041 /* Run main MD idle handler. */
3042 atomic_store_int(&tdq->tdq_cpu_idle, 1);
3043 /*
3044 * Make sure that the tdq_cpu_idle update is globally visible
3045 * before cpu_idle() reads tdq_load. The order is important
3046 * to avoid races with tdq_notify().
3047 */
3048 atomic_thread_fence_seq_cst();
3049 /*
3050 * Checking for again after the fence picks up assigned
3051 * threads often enough to make it worthwhile to do so in
3052 * order to avoid calling cpu_idle().
3053 */
3054 if (TDQ_LOAD(tdq) != 0) {
3055 atomic_store_int(&tdq->tdq_cpu_idle, 0);
3056 continue;
3057 }
3058 cpu_idle(switchcnt * 4 > sched_idlespinthresh);
3059 atomic_store_int(&tdq->tdq_cpu_idle, 0);
3060
3061 /*
3062 * Account thread-less hardware interrupts and
3063 * other wakeup reasons equal to context switches.
3064 */
3065 switchcnt = TDQ_SWITCHCNT(tdq);
3066 if (switchcnt != oldswitchcnt)
3067 continue;
3068 TDQ_SWITCHCNT_INC(tdq);
3069 oldswitchcnt++;
3070 }
3071 }
3072
3073 /*
3074 * sched_throw_grab() chooses a thread from the queue to switch to
3075 * next. It returns with the tdq lock dropped in a spinlock section to
3076 * keep interrupts disabled until the CPU is running in a proper threaded
3077 * context.
3078 */
3079 static struct thread *
sched_throw_grab(struct tdq * tdq)3080 sched_throw_grab(struct tdq *tdq)
3081 {
3082 struct thread *newtd;
3083
3084 newtd = choosethread();
3085 spinlock_enter();
3086 TDQ_UNLOCK(tdq);
3087 KASSERT(curthread->td_md.md_spinlock_count == 1,
3088 ("invalid count %d", curthread->td_md.md_spinlock_count));
3089 return (newtd);
3090 }
3091
3092 /*
3093 * A CPU is entering for the first time.
3094 */
3095 void
sched_ap_entry(void)3096 sched_ap_entry(void)
3097 {
3098 struct thread *newtd;
3099 struct tdq *tdq;
3100
3101 tdq = TDQ_SELF();
3102
3103 /* This should have been setup in schedinit_ap(). */
3104 THREAD_LOCKPTR_ASSERT(curthread, TDQ_LOCKPTR(tdq));
3105
3106 TDQ_LOCK(tdq);
3107 /* Correct spinlock nesting. */
3108 spinlock_exit();
3109 PCPU_SET(switchtime, cpu_ticks());
3110 PCPU_SET(switchticks, ticks);
3111
3112 newtd = sched_throw_grab(tdq);
3113
3114 /* doesn't return */
3115 cpu_throw(NULL, newtd);
3116 }
3117
3118 /*
3119 * A thread is exiting.
3120 */
3121 void
sched_throw(struct thread * td)3122 sched_throw(struct thread *td)
3123 {
3124 struct thread *newtd;
3125 struct tdq *tdq;
3126
3127 tdq = TDQ_SELF();
3128
3129 MPASS(td != NULL);
3130 THREAD_LOCK_ASSERT(td, MA_OWNED);
3131 THREAD_LOCKPTR_ASSERT(td, TDQ_LOCKPTR(tdq));
3132
3133 tdq_load_rem(tdq, td);
3134 td->td_lastcpu = td->td_oncpu;
3135 td->td_oncpu = NOCPU;
3136 thread_lock_block(td);
3137
3138 newtd = sched_throw_grab(tdq);
3139
3140 /* doesn't return */
3141 cpu_switch(td, newtd, TDQ_LOCKPTR(tdq));
3142 }
3143
3144 /*
3145 * This is called from fork_exit(). Just acquire the correct locks and
3146 * let fork do the rest of the work.
3147 */
3148 void
sched_fork_exit(struct thread * td)3149 sched_fork_exit(struct thread *td)
3150 {
3151 struct tdq *tdq;
3152 int cpuid;
3153
3154 /*
3155 * Finish setting up thread glue so that it begins execution in a
3156 * non-nested critical section with the scheduler lock held.
3157 */
3158 KASSERT(curthread->td_md.md_spinlock_count == 1,
3159 ("invalid count %d", curthread->td_md.md_spinlock_count));
3160 cpuid = PCPU_GET(cpuid);
3161 tdq = TDQ_SELF();
3162 TDQ_LOCK(tdq);
3163 spinlock_exit();
3164 MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
3165 td->td_oncpu = cpuid;
3166 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
3167 "prio:%d", td->td_priority);
3168 SDT_PROBE0(sched, , , on__cpu);
3169 }
3170
3171 /*
3172 * Create on first use to catch odd startup conditions.
3173 */
3174 char *
sched_tdname(struct thread * td)3175 sched_tdname(struct thread *td)
3176 {
3177 #ifdef KTR
3178 struct td_sched *ts;
3179
3180 ts = td_get_sched(td);
3181 if (ts->ts_name[0] == '\0')
3182 snprintf(ts->ts_name, sizeof(ts->ts_name),
3183 "%s tid %d", td->td_name, td->td_tid);
3184 return (ts->ts_name);
3185 #else
3186 return (td->td_name);
3187 #endif
3188 }
3189
3190 #ifdef KTR
3191 void
sched_clear_tdname(struct thread * td)3192 sched_clear_tdname(struct thread *td)
3193 {
3194 struct td_sched *ts;
3195
3196 ts = td_get_sched(td);
3197 ts->ts_name[0] = '\0';
3198 }
3199 #endif
3200
3201 #ifdef SMP
3202
3203 /*
3204 * Build the CPU topology dump string. Is recursively called to collect
3205 * the topology tree.
3206 */
3207 static int
sysctl_kern_sched_topology_spec_internal(struct sbuf * sb,struct cpu_group * cg,int indent)3208 sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
3209 int indent)
3210 {
3211 char cpusetbuf[CPUSETBUFSIZ];
3212 int i, first;
3213
3214 sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
3215 "", 1 + indent / 2, cg->cg_level);
3216 sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "",
3217 cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask));
3218 first = TRUE;
3219 for (i = cg->cg_first; i <= cg->cg_last; i++) {
3220 if (CPU_ISSET(i, &cg->cg_mask)) {
3221 if (!first)
3222 sbuf_cat(sb, ", ");
3223 else
3224 first = FALSE;
3225 sbuf_printf(sb, "%d", i);
3226 }
3227 }
3228 sbuf_cat(sb, "</cpu>\n");
3229
3230 if (cg->cg_flags != 0) {
3231 sbuf_printf(sb, "%*s <flags>", indent, "");
3232 if ((cg->cg_flags & CG_FLAG_HTT) != 0)
3233 sbuf_cat(sb, "<flag name=\"HTT\">HTT group</flag>");
3234 if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
3235 sbuf_cat(sb, "<flag name=\"THREAD\">THREAD group</flag>");
3236 if ((cg->cg_flags & CG_FLAG_SMT) != 0)
3237 sbuf_cat(sb, "<flag name=\"SMT\">SMT group</flag>");
3238 if ((cg->cg_flags & CG_FLAG_NODE) != 0)
3239 sbuf_cat(sb, "<flag name=\"NODE\">NUMA node</flag>");
3240 sbuf_cat(sb, "</flags>\n");
3241 }
3242
3243 if (cg->cg_children > 0) {
3244 sbuf_printf(sb, "%*s <children>\n", indent, "");
3245 for (i = 0; i < cg->cg_children; i++)
3246 sysctl_kern_sched_topology_spec_internal(sb,
3247 &cg->cg_child[i], indent+2);
3248 sbuf_printf(sb, "%*s </children>\n", indent, "");
3249 }
3250 sbuf_printf(sb, "%*s</group>\n", indent, "");
3251 return (0);
3252 }
3253
3254 /*
3255 * Sysctl handler for retrieving topology dump. It's a wrapper for
3256 * the recursive sysctl_kern_smp_topology_spec_internal().
3257 */
3258 static int
sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)3259 sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
3260 {
3261 struct sbuf *topo;
3262 int err;
3263
3264 KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
3265
3266 topo = sbuf_new_for_sysctl(NULL, NULL, 512, req);
3267 if (topo == NULL)
3268 return (ENOMEM);
3269
3270 sbuf_cat(topo, "<groups>\n");
3271 err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
3272 sbuf_cat(topo, "</groups>\n");
3273
3274 if (err == 0) {
3275 err = sbuf_finish(topo);
3276 }
3277 sbuf_delete(topo);
3278 return (err);
3279 }
3280
3281 #endif
3282
3283 static int
sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)3284 sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
3285 {
3286 int error, new_val, period;
3287
3288 period = 1000000 / realstathz;
3289 new_val = period * sched_slice;
3290 error = sysctl_handle_int(oidp, &new_val, 0, req);
3291 if (error != 0 || req->newptr == NULL)
3292 return (error);
3293 if (new_val <= 0)
3294 return (EINVAL);
3295 sched_slice = imax(1, (new_val + period / 2) / period);
3296 sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
3297 hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
3298 realstathz);
3299 return (0);
3300 }
3301
3302 SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
3303 "Scheduler");
3304 SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
3305 "Scheduler name");
3306 SYSCTL_PROC(_kern_sched, OID_AUTO, quantum,
3307 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
3308 sysctl_kern_quantum, "I",
3309 "Quantum for timeshare threads in microseconds");
3310 SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
3311 "Quantum for timeshare threads in stathz ticks");
3312 SYSCTL_UINT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
3313 "Interactivity score threshold");
3314 SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW,
3315 &preempt_thresh, 0,
3316 "Maximal (lowest) priority for preemption");
3317 SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0,
3318 "Assign static kernel priorities to sleeping threads");
3319 SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0,
3320 "Number of times idle thread will spin waiting for new work");
3321 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW,
3322 &sched_idlespinthresh, 0,
3323 "Threshold before we will permit idle thread spinning");
3324 #ifdef SMP
3325 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
3326 "Number of hz ticks to keep thread affinity for");
3327 SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
3328 "Enables the long-term load balancer");
3329 SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
3330 &balance_interval, 0,
3331 "Average period in stathz ticks to run the long-term balancer");
3332 SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
3333 "Attempts to steal work from other cores before idling");
3334 SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
3335 "Minimum load on remote CPU before we'll steal");
3336 SYSCTL_INT(_kern_sched, OID_AUTO, trysteal_limit, CTLFLAG_RW, &trysteal_limit,
3337 0, "Topological distance limit for stealing threads in sched_switch()");
3338 SYSCTL_INT(_kern_sched, OID_AUTO, always_steal, CTLFLAG_RW, &always_steal, 0,
3339 "Always run the stealer from the idle thread");
3340 SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
3341 CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
3342 "XML dump of detected CPU topology");
3343 #endif
3344
3345 /* ps compat. All cpu percentages from ULE are weighted. */
3346 static int ccpu = 0;
3347 SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0,
3348 "Decay factor used for updating %CPU in 4BSD scheduler");
3349