1 /* 2 * Copyright (c) 1999 Peter Wemm <peter@FreeBSD.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 * 26 * $DragonFly: src/sys/kern/usched_bsd4.c,v 1.15 2006/06/20 18:44:32 dillon Exp $ 27 */ 28 29 #include <sys/param.h> 30 #include <sys/systm.h> 31 #include <sys/kernel.h> 32 #include <sys/lock.h> 33 #include <sys/queue.h> 34 #include <sys/proc.h> 35 #include <sys/rtprio.h> 36 #include <sys/uio.h> 37 #include <sys/sysctl.h> 38 #include <sys/resourcevar.h> 39 #include <sys/spinlock.h> 40 #include <machine/ipl.h> 41 #include <machine/cpu.h> 42 #include <machine/smp.h> 43 44 #include <sys/thread2.h> 45 #include <sys/spinlock2.h> 46 47 /* 48 * Priorities. Note that with 32 run queues per scheduler each queue 49 * represents four priority levels. 50 */ 51 52 #define MAXPRI 128 53 #define PRIMASK (MAXPRI - 1) 54 #define PRIBASE_REALTIME 0 55 #define PRIBASE_NORMAL MAXPRI 56 #define PRIBASE_IDLE (MAXPRI * 2) 57 #define PRIBASE_THREAD (MAXPRI * 3) 58 #define PRIBASE_NULL (MAXPRI * 4) 59 60 #define NQS 32 /* 32 run queues. */ 61 #define PPQ (MAXPRI / NQS) /* priorities per queue */ 62 #define PPQMASK (PPQ - 1) 63 64 /* 65 * NICEPPQ - number of nice units per priority queue 66 * ESTCPURAMP - number of scheduler ticks for estcpu to switch queues 67 * 68 * ESTCPUPPQ - number of estcpu units per priority queue 69 * ESTCPUMAX - number of estcpu units 70 * ESTCPUINCR - amount we have to increment p_estcpu per scheduling tick at 71 * 100% cpu. 72 */ 73 #define NICEPPQ 2 74 #define ESTCPURAMP 4 75 #define ESTCPUPPQ 512 76 #define ESTCPUMAX (ESTCPUPPQ * NQS) 77 #define ESTCPUINCR (ESTCPUPPQ / ESTCPURAMP) 78 #define PRIO_RANGE (PRIO_MAX - PRIO_MIN + 1) 79 80 #define ESTCPULIM(v) min((v), ESTCPUMAX) 81 82 TAILQ_HEAD(rq, lwp); 83 84 #define lwp_priority lwp_usdata.bsd4.priority 85 #define lwp_rqindex lwp_usdata.bsd4.rqindex 86 #define lwp_origcpu lwp_usdata.bsd4.origcpu 87 #define lwp_estcpu lwp_usdata.bsd4.estcpu 88 #define lwp_rqtype lwp_usdata.bsd4.rqtype 89 90 static void bsd4_acquire_curproc(struct lwp *lp); 91 static void bsd4_release_curproc(struct lwp *lp); 92 static void bsd4_select_curproc(globaldata_t gd); 93 static void bsd4_setrunqueue(struct lwp *lp); 94 static void bsd4_schedulerclock(struct lwp *lp, sysclock_t period, 95 sysclock_t cpstamp); 96 static void bsd4_recalculate_estcpu(struct lwp *lp); 97 static void bsd4_resetpriority(struct lwp *lp); 98 static void bsd4_forking(struct lwp *plp, struct lwp *lp); 99 static void bsd4_exiting(struct lwp *plp, struct lwp *lp); 100 101 #ifdef SMP 102 static void need_user_resched_remote(void *dummy); 103 #endif 104 static struct lwp *chooseproc_locked(struct lwp *chklp); 105 static void bsd4_remrunqueue_locked(struct lwp *lp); 106 static void bsd4_setrunqueue_locked(struct lwp *lp); 107 108 struct usched usched_bsd4 = { 109 { NULL }, 110 "bsd4", "Original DragonFly Scheduler", 111 NULL, /* default registration */ 112 NULL, /* default deregistration */ 113 bsd4_acquire_curproc, 114 bsd4_release_curproc, 115 bsd4_setrunqueue, 116 bsd4_schedulerclock, 117 bsd4_recalculate_estcpu, 118 bsd4_resetpriority, 119 bsd4_forking, 120 bsd4_exiting, 121 NULL /* setcpumask not supported */ 122 }; 123 124 struct usched_bsd4_pcpu { 125 struct thread helper_thread; 126 short rrcount; 127 short upri; 128 struct lwp *uschedcp; 129 }; 130 131 typedef struct usched_bsd4_pcpu *bsd4_pcpu_t; 132 133 /* 134 * We have NQS (32) run queues per scheduling class. For the normal 135 * class, there are 128 priorities scaled onto these 32 queues. New 136 * processes are added to the last entry in each queue, and processes 137 * are selected for running by taking them from the head and maintaining 138 * a simple FIFO arrangement. Realtime and Idle priority processes have 139 * and explicit 0-31 priority which maps directly onto their class queue 140 * index. When a queue has something in it, the corresponding bit is 141 * set in the queuebits variable, allowing a single read to determine 142 * the state of all 32 queues and then a ffs() to find the first busy 143 * queue. 144 */ 145 static struct rq bsd4_queues[NQS]; 146 static struct rq bsd4_rtqueues[NQS]; 147 static struct rq bsd4_idqueues[NQS]; 148 static u_int32_t bsd4_queuebits; 149 static u_int32_t bsd4_rtqueuebits; 150 static u_int32_t bsd4_idqueuebits; 151 static cpumask_t bsd4_curprocmask = -1; /* currently running a user process */ 152 static cpumask_t bsd4_rdyprocmask; /* ready to accept a user process */ 153 static int bsd4_runqcount; 154 #ifdef SMP 155 static volatile int bsd4_scancpu; 156 #endif 157 static struct spinlock bsd4_spin; 158 static struct usched_bsd4_pcpu bsd4_pcpu[MAXCPU]; 159 160 SYSCTL_INT(_debug, OID_AUTO, bsd4_runqcount, CTLFLAG_RD, &bsd4_runqcount, 0, ""); 161 #ifdef INVARIANTS 162 static int usched_nonoptimal; 163 SYSCTL_INT(_debug, OID_AUTO, usched_nonoptimal, CTLFLAG_RW, 164 &usched_nonoptimal, 0, "acquire_curproc() was not optimal"); 165 static int usched_optimal; 166 SYSCTL_INT(_debug, OID_AUTO, usched_optimal, CTLFLAG_RW, 167 &usched_optimal, 0, "acquire_curproc() was optimal"); 168 #endif 169 static int usched_debug = -1; 170 SYSCTL_INT(_debug, OID_AUTO, scdebug, CTLFLAG_RW, &usched_debug, 0, ""); 171 #ifdef SMP 172 static int remote_resched_nonaffinity; 173 static int remote_resched_affinity; 174 static int choose_affinity; 175 SYSCTL_INT(_debug, OID_AUTO, remote_resched_nonaffinity, CTLFLAG_RD, 176 &remote_resched_nonaffinity, 0, "Number of remote rescheds"); 177 SYSCTL_INT(_debug, OID_AUTO, remote_resched_affinity, CTLFLAG_RD, 178 &remote_resched_affinity, 0, "Number of remote rescheds"); 179 SYSCTL_INT(_debug, OID_AUTO, choose_affinity, CTLFLAG_RD, 180 &choose_affinity, 0, "chooseproc() was smart"); 181 #endif 182 183 static int usched_bsd4_rrinterval = (ESTCPUFREQ + 9) / 10; 184 SYSCTL_INT(_kern, OID_AUTO, usched_bsd4_rrinterval, CTLFLAG_RW, 185 &usched_bsd4_rrinterval, 0, ""); 186 static int usched_bsd4_decay = ESTCPUINCR / 2; 187 SYSCTL_INT(_kern, OID_AUTO, usched_bsd4_decay, CTLFLAG_RW, 188 &usched_bsd4_decay, 0, ""); 189 190 /* 191 * Initialize the run queues at boot time. 192 */ 193 static void 194 rqinit(void *dummy) 195 { 196 int i; 197 198 spin_init(&bsd4_spin); 199 for (i = 0; i < NQS; i++) { 200 TAILQ_INIT(&bsd4_queues[i]); 201 TAILQ_INIT(&bsd4_rtqueues[i]); 202 TAILQ_INIT(&bsd4_idqueues[i]); 203 } 204 atomic_clear_int(&bsd4_curprocmask, 1); 205 } 206 SYSINIT(runqueue, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, rqinit, NULL) 207 208 /* 209 * BSD4_ACQUIRE_CURPROC 210 * 211 * This function is called when the kernel intends to return to userland. 212 * It is responsible for making the thread the current designated userland 213 * thread for this cpu, blocking if necessary. 214 * 215 * We are expected to handle userland reschedule requests here too. 216 * 217 * WARNING! THIS FUNCTION IS ALLOWED TO CAUSE THE CURRENT THREAD TO MIGRATE 218 * TO ANOTHER CPU! Because most of the kernel assumes that no migration will 219 * occur, this function is called only under very controlled circumstances. 220 * 221 * Basically we recalculate our estcpu to hopefully give us a more 222 * favorable disposition, setrunqueue, then wait for the curlwp 223 * designation to be handed to us (if the setrunqueue didn't do it). 224 * 225 * MPSAFE 226 */ 227 static void 228 bsd4_acquire_curproc(struct lwp *lp) 229 { 230 globaldata_t gd = mycpu; 231 bsd4_pcpu_t dd = &bsd4_pcpu[gd->gd_cpuid]; 232 233 /* 234 * Possibly select another thread, or keep the current thread. 235 */ 236 if (user_resched_wanted()) 237 bsd4_select_curproc(gd); 238 239 /* 240 * If uschedcp is still pointing to us, we're done 241 */ 242 if (dd->uschedcp == lp) 243 return; 244 245 /* 246 * If this cpu has no current thread, and the run queue is 247 * empty, we can safely select ourself. 248 */ 249 if (dd->uschedcp == NULL && bsd4_runqcount == 0) { 250 atomic_set_int(&bsd4_curprocmask, gd->gd_cpumask); 251 dd->uschedcp = lp; 252 dd->upri = lp->lwp_priority; 253 return; 254 } 255 256 /* 257 * Adjust estcpu and recalculate our priority, then put us back on 258 * the user process scheduler's runq. Only increment the involuntary 259 * context switch count if the setrunqueue call did not immediately 260 * schedule us. 261 * 262 * Loop until we become the currently scheduled process. Note that 263 * calling setrunqueue can cause us to be migrated to another cpu 264 * after we switch away. 265 */ 266 do { 267 crit_enter(); 268 bsd4_recalculate_estcpu(lp); 269 lwkt_deschedule_self(gd->gd_curthread); 270 bsd4_setrunqueue(lp); 271 if ((gd->gd_curthread->td_flags & TDF_RUNQ) == 0) 272 ++lp->lwp_stats->p_ru.ru_nivcsw; 273 lwkt_switch(); 274 crit_exit(); 275 gd = mycpu; 276 dd = &bsd4_pcpu[gd->gd_cpuid]; 277 } while (dd->uschedcp != lp); 278 KKASSERT((lp->lwp_proc->p_flag & P_ONRUNQ) == 0); 279 } 280 281 /* 282 * BSD4_RELEASE_CURPROC 283 * 284 * This routine detaches the current thread from the userland scheduler, 285 * usually because the thread needs to run in the kernel (at kernel priority) 286 * for a while. 287 * 288 * This routine is also responsible for selecting a new thread to 289 * make the current thread. 290 * 291 * NOTE: This implementation differs from the dummy example in that 292 * bsd4_select_curproc() is able to select the current process, whereas 293 * dummy_select_curproc() is not able to select the current process. 294 * This means we have to NULL out uschedcp. 295 * 296 * Additionally, note that we may already be on a run queue if releasing 297 * via the lwkt_switch() in bsd4_setrunqueue(). 298 * 299 * WARNING! The MP lock may be in an unsynchronized state due to the 300 * way get_mplock() works and the fact that this function may be called 301 * from a passive release during a lwkt_switch(). try_mplock() will deal 302 * with this for us but you should be aware that td_mpcount may not be 303 * useable. 304 * 305 * MPSAFE 306 */ 307 static void 308 bsd4_release_curproc(struct lwp *lp) 309 { 310 globaldata_t gd = mycpu; 311 bsd4_pcpu_t dd = &bsd4_pcpu[gd->gd_cpuid]; 312 313 if (dd->uschedcp == lp) { 314 /* 315 * Note: we leave ou curprocmask bit set to prevent 316 * unnecessary scheduler helper wakeups. 317 * bsd4_select_curproc() will clean it up. 318 */ 319 KKASSERT((lp->lwp_proc->p_flag & P_ONRUNQ) == 0); 320 dd->uschedcp = NULL; /* don't let lp be selected */ 321 bsd4_select_curproc(gd); 322 } 323 } 324 325 /* 326 * BSD4_SELECT_CURPROC 327 * 328 * Select a new current process for this cpu. This satisfies a user 329 * scheduler reschedule request so clear that too. 330 * 331 * This routine is also responsible for equal-priority round-robining, 332 * typically triggered from bsd4_schedulerclock(). In our dummy example 333 * all the 'user' threads are LWKT scheduled all at once and we just 334 * call lwkt_switch(). 335 * 336 * MPSAFE 337 */ 338 static 339 void 340 bsd4_select_curproc(globaldata_t gd) 341 { 342 bsd4_pcpu_t dd = &bsd4_pcpu[gd->gd_cpuid]; 343 struct lwp *nlp; 344 int cpuid = gd->gd_cpuid; 345 346 crit_enter_gd(gd); 347 clear_user_resched(); /* This satisfied the reschedule request */ 348 dd->rrcount = 0; /* Reset the round-robin counter */ 349 350 spin_lock_wr(&bsd4_spin); 351 if ((nlp = chooseproc_locked(dd->uschedcp)) != NULL) { 352 atomic_set_int(&bsd4_curprocmask, 1 << cpuid); 353 dd->upri = nlp->lwp_priority; 354 dd->uschedcp = nlp; 355 spin_unlock_wr(&bsd4_spin); 356 #ifdef SMP 357 lwkt_acquire(nlp->lwp_thread); 358 #endif 359 lwkt_schedule(nlp->lwp_thread); 360 } else if (dd->uschedcp) { 361 dd->upri = dd->uschedcp->lwp_priority; 362 spin_unlock_wr(&bsd4_spin); 363 KKASSERT(bsd4_curprocmask & (1 << cpuid)); 364 } else if (bsd4_runqcount && (bsd4_rdyprocmask & (1 << cpuid))) { 365 atomic_clear_int(&bsd4_curprocmask, 1 << cpuid); 366 atomic_clear_int(&bsd4_rdyprocmask, 1 << cpuid); 367 dd->uschedcp = NULL; 368 dd->upri = PRIBASE_NULL; 369 spin_unlock_wr(&bsd4_spin); 370 lwkt_schedule(&dd->helper_thread); 371 } else { 372 dd->uschedcp = NULL; 373 dd->upri = PRIBASE_NULL; 374 atomic_clear_int(&bsd4_curprocmask, 1 << cpuid); 375 spin_unlock_wr(&bsd4_spin); 376 } 377 crit_exit_gd(gd); 378 } 379 380 /* 381 * BSD4_SETRUNQUEUE 382 * 383 * This routine is called to schedule a new user process after a fork. 384 * 385 * The caller may set P_PASSIVE_ACQ in p_flag to indicate that we should 386 * attempt to leave the thread on the current cpu. 387 * 388 * If P_PASSIVE_ACQ is set setrunqueue() will not wakeup potential target 389 * cpus in an attempt to keep the process on the current cpu at least for 390 * a little while to take advantage of locality of reference (e.g. fork/exec 391 * or short fork/exit, and uio_yield()). 392 * 393 * CPU AFFINITY: cpu affinity is handled by attempting to either schedule 394 * or (user level) preempt on the same cpu that a process was previously 395 * scheduled to. If we cannot do this but we are at enough of a higher 396 * priority then the processes running on other cpus, we will allow the 397 * process to be stolen by another cpu. 398 * 399 * WARNING! This routine cannot block. bsd4_acquire_curproc() does 400 * a deschedule/switch interlock and we can be moved to another cpu 401 * the moment we are switched out. Our LWKT run state is the only 402 * thing preventing the transfer. 403 * 404 * The associated thread must NOT currently be scheduled (but can be the 405 * current process after it has been LWKT descheduled). It must NOT be on 406 * a bsd4 scheduler queue either. The purpose of this routine is to put 407 * it on a scheduler queue or make it the current user process and LWKT 408 * schedule it. It is possible that the thread is in the middle of a LWKT 409 * switchout on another cpu, lwkt_acquire() deals with that case. 410 * 411 * The process must be runnable. 412 * 413 * MPSAFE 414 */ 415 static void 416 bsd4_setrunqueue(struct lwp *lp) 417 { 418 globaldata_t gd; 419 bsd4_pcpu_t dd; 420 int cpuid; 421 #ifdef SMP 422 cpumask_t mask; 423 cpumask_t tmpmask; 424 #endif 425 426 /* 427 * First validate the process state relative to the current cpu. 428 * We don't need the spinlock for this, just a critical section. 429 * We are in control of the process. 430 */ 431 crit_enter(); 432 KASSERT(lp->lwp_proc->p_stat == SRUN, ("setrunqueue: proc not SRUN")); 433 KASSERT((lp->lwp_proc->p_flag & P_ONRUNQ) == 0, 434 ("lwp %d/%d already on runq! flag %08x", lp->lwp_proc->p_pid, 435 lp->lwp_tid, lp->lwp_proc->p_flag)); 436 KKASSERT((lp->lwp_thread->td_flags & TDF_RUNQ) == 0); 437 438 /* 439 * Note: gd and dd are relative to the target thread's last cpu, 440 * NOT our current cpu. 441 */ 442 gd = lp->lwp_thread->td_gd; 443 dd = &bsd4_pcpu[gd->gd_cpuid]; 444 445 /* 446 * If setrunqueue is being called due to being woken up, verses 447 * being called when aquiring the current process, recalculate 448 * estcpu. 449 * 450 * Because recalculate is only called once or twice for long sleeps, 451 * not every second forever while the process is sleeping, we have 452 * to manually call it to resynchronize p_cpbase on wakeup or it 453 * will wrap if the process was sleeping long enough (e.g. ~10 min 454 * with the ACPI timer) and really mess up the nticks calculation. 455 * 456 * NOTE: because P_ONRUNQ is not set, bsd4_recalculate_estcpu()'s 457 * calls to resetpriority will just play with the processes priority 458 * fields and not mess with any queues, so it is MPSAFE in this 459 * context. 460 */ 461 if (lp->lwp_slptime && (lp->lwp_thread->td_flags & TDF_RUNNING) == 0) { 462 bsd4_recalculate_estcpu(lp); 463 lp->lwp_slptime = 0; 464 } 465 466 /* 467 * This process is not supposed to be scheduled anywhere or assigned 468 * as the current process anywhere. Assert the condition. 469 */ 470 KKASSERT(dd->uschedcp != lp); 471 472 /* 473 * Check local cpu affinity. The associated thread is stable at 474 * the moment. Note that we may be checking another cpu here so we 475 * have to be careful. We can only assign uschedcp on OUR cpu. 476 * 477 * This allows us to avoid actually queueing the process. 478 * acquire_curproc() will handle any threads we mistakenly schedule. 479 */ 480 cpuid = gd->gd_cpuid; 481 if (gd == mycpu && (bsd4_curprocmask & (1 << cpuid)) == 0) { 482 atomic_set_int(&bsd4_curprocmask, 1 << cpuid); 483 dd->uschedcp = lp; 484 dd->upri = lp->lwp_priority; 485 lwkt_schedule(lp->lwp_thread); 486 crit_exit(); 487 return; 488 } 489 490 /* 491 * gd and cpuid may still 'hint' at another cpu. Even so we have 492 * to place this process on the userland scheduler's run queue for 493 * action by the target cpu. 494 */ 495 #ifdef SMP 496 /* 497 * XXX fixme. Could be part of a remrunqueue/setrunqueue 498 * operation when the priority is recalculated, so TDF_MIGRATING 499 * may already be set. 500 */ 501 if ((lp->lwp_thread->td_flags & TDF_MIGRATING) == 0) 502 lwkt_giveaway(lp->lwp_thread); 503 #endif 504 505 /* 506 * We lose control of lp the moment we release the spinlock after 507 * having placed lp on the queue. i.e. another cpu could pick it 508 * up and it could exit, or its priority could be further adjusted, 509 * or something like that. 510 */ 511 spin_lock_wr(&bsd4_spin); 512 bsd4_setrunqueue_locked(lp); 513 514 /* 515 * gd, dd, and cpuid are still our target cpu 'hint', not our current 516 * cpu info. 517 * 518 * We always try to schedule a LWP to its original cpu first. It 519 * is possible for the scheduler helper or setrunqueue to assign 520 * the LWP to a different cpu before the one we asked for wakes 521 * up. 522 * 523 * If the LWP has higher priority (lower lwp_priority value) on 524 * its target cpu, reschedule on that cpu. 525 */ 526 if ((lp->lwp_thread->td_flags & TDF_NORESCHED) == 0) { 527 if ((dd->upri & ~PRIMASK) > (lp->lwp_priority & ~PRIMASK)) { 528 dd->upri = lp->lwp_priority; 529 spin_unlock_wr(&bsd4_spin); 530 #ifdef SMP 531 if (gd == mycpu) { 532 need_user_resched(); 533 } else { 534 lwkt_send_ipiq(gd, need_user_resched_remote, 535 NULL); 536 } 537 #else 538 need_user_resched(); 539 #endif 540 crit_exit(); 541 return; 542 } 543 } 544 spin_unlock_wr(&bsd4_spin); 545 546 #ifdef SMP 547 /* 548 * Otherwise the LWP has a lower priority or we were asked not 549 * to reschedule. Look for an idle cpu whos scheduler helper 550 * is ready to accept more work. 551 * 552 * Look for an idle cpu starting at our rotator (bsd4_scancpu). 553 * 554 * If no cpus are ready to accept work, just return. 555 * 556 * XXX P_PASSIVE_ACQ 557 */ 558 mask = ~bsd4_curprocmask & bsd4_rdyprocmask & mycpu->gd_other_cpus & 559 lp->lwp_cpumask; 560 if (mask) { 561 cpuid = bsd4_scancpu; 562 if (++cpuid == ncpus) 563 cpuid = 0; 564 tmpmask = ~((1 << cpuid) - 1); 565 if (mask & tmpmask) 566 cpuid = bsfl(mask & tmpmask); 567 else 568 cpuid = bsfl(mask); 569 atomic_clear_int(&bsd4_rdyprocmask, 1 << cpuid); 570 bsd4_scancpu = cpuid; 571 lwkt_schedule(&bsd4_pcpu[cpuid].helper_thread); 572 } 573 #endif 574 crit_exit(); 575 } 576 577 /* 578 * This routine is called from a systimer IPI. It MUST be MP-safe and 579 * the BGL IS NOT HELD ON ENTRY. This routine is called at ESTCPUFREQ on 580 * each cpu. 581 * 582 * Because this is effectively a 'fast' interrupt, we cannot safely 583 * use spinlocks unless gd_spinlock_rd is NULL and gd_spinlocks_wr is 0, 584 * even if the spinlocks are 'non conflicting'. This is due to the way 585 * spinlock conflicts against cached read locks are handled. 586 * 587 * MPSAFE 588 */ 589 static 590 void 591 bsd4_schedulerclock(struct lwp *lp, sysclock_t period, sysclock_t cpstamp) 592 { 593 globaldata_t gd = mycpu; 594 bsd4_pcpu_t dd = &bsd4_pcpu[gd->gd_cpuid]; 595 596 /* 597 * Do we need to round-robin? We round-robin 10 times a second. 598 * This should only occur for cpu-bound batch processes. 599 */ 600 if (++dd->rrcount >= usched_bsd4_rrinterval) { 601 dd->rrcount = 0; 602 need_user_resched(); 603 } 604 605 /* 606 * As the process accumulates cpu time p_estcpu is bumped and may 607 * push the process into another scheduling queue. It typically 608 * takes 4 ticks to bump the queue. 609 */ 610 lp->lwp_estcpu = ESTCPULIM(lp->lwp_estcpu + ESTCPUINCR); 611 612 /* 613 * Reducing p_origcpu over time causes more of our estcpu to be 614 * returned to the parent when we exit. This is a small tweak 615 * for the batch detection heuristic. 616 */ 617 if (lp->lwp_origcpu) 618 --lp->lwp_origcpu; 619 620 /* 621 * We can only safely call bsd4_resetpriority(), which uses spinlocks, 622 * if we aren't interrupting a thread that is using spinlocks. 623 * Otherwise we can deadlock with another cpu waiting for our read 624 * spinlocks to clear. 625 */ 626 if (gd->gd_spinlock_rd == NULL && gd->gd_spinlocks_wr == 0) 627 bsd4_resetpriority(lp); 628 else 629 need_user_resched(); 630 } 631 632 /* 633 * Called from acquire and from kern_synch's one-second timer (one of the 634 * callout helper threads) with a critical section held. 635 * 636 * Decay p_estcpu based on the number of ticks we haven't been running 637 * and our p_nice. As the load increases each process observes a larger 638 * number of idle ticks (because other processes are running in them). 639 * This observation leads to a larger correction which tends to make the 640 * system more 'batchy'. 641 * 642 * Note that no recalculation occurs for a process which sleeps and wakes 643 * up in the same tick. That is, a system doing thousands of context 644 * switches per second will still only do serious estcpu calculations 645 * ESTCPUFREQ times per second. 646 * 647 * MPSAFE 648 */ 649 static 650 void 651 bsd4_recalculate_estcpu(struct lwp *lp) 652 { 653 globaldata_t gd = mycpu; 654 sysclock_t cpbase; 655 int loadfac; 656 int ndecay; 657 int nticks; 658 int nleft; 659 660 /* 661 * We have to subtract periodic to get the last schedclock 662 * timeout time, otherwise we would get the upcoming timeout. 663 * Keep in mind that a process can migrate between cpus and 664 * while the scheduler clock should be very close, boundary 665 * conditions could lead to a small negative delta. 666 */ 667 cpbase = gd->gd_schedclock.time - gd->gd_schedclock.periodic; 668 669 if (lp->lwp_slptime > 1) { 670 /* 671 * Too much time has passed, do a coarse correction. 672 */ 673 lp->lwp_estcpu = lp->lwp_estcpu >> 1; 674 bsd4_resetpriority(lp); 675 lp->lwp_cpbase = cpbase; 676 lp->lwp_cpticks = 0; 677 } else if (lp->lwp_cpbase != cpbase) { 678 /* 679 * Adjust estcpu if we are in a different tick. Don't waste 680 * time if we are in the same tick. 681 * 682 * First calculate the number of ticks in the measurement 683 * interval. The nticks calculation can wind up 0 due to 684 * a bug in the handling of lwp_slptime (as yet not found), 685 * so make sure we do not get a divide by 0 panic. 686 */ 687 nticks = (cpbase - lp->lwp_cpbase) / gd->gd_schedclock.periodic; 688 if (nticks <= 0) 689 nticks = 1; 690 updatepcpu(lp, lp->lwp_cpticks, nticks); 691 692 if ((nleft = nticks - lp->lwp_cpticks) < 0) 693 nleft = 0; 694 if (usched_debug == lp->lwp_proc->p_pid) { 695 printf("pid %d tid %d estcpu %d cpticks %d nticks %d nleft %d", 696 lp->lwp_proc->p_pid, lp->lwp_tid, lp->lwp_estcpu, 697 lp->lwp_cpticks, nticks, nleft); 698 } 699 700 /* 701 * Calculate a decay value based on ticks remaining scaled 702 * down by the instantanious load and p_nice. 703 */ 704 if ((loadfac = bsd4_runqcount) < 2) 705 loadfac = 2; 706 ndecay = nleft * usched_bsd4_decay * 2 * 707 (PRIO_MAX * 2 - lp->lwp_proc->p_nice) / (loadfac * PRIO_MAX * 2); 708 709 /* 710 * Adjust p_estcpu. Handle a border case where batch jobs 711 * can get stalled long enough to decay to zero when they 712 * shouldn't. 713 */ 714 if (lp->lwp_estcpu > ndecay * 2) 715 lp->lwp_estcpu -= ndecay; 716 else 717 lp->lwp_estcpu >>= 1; 718 719 if (usched_debug == lp->lwp_proc->p_pid) 720 printf(" ndecay %d estcpu %d\n", ndecay, lp->lwp_estcpu); 721 bsd4_resetpriority(lp); 722 lp->lwp_cpbase = cpbase; 723 lp->lwp_cpticks = 0; 724 } 725 } 726 727 /* 728 * Compute the priority of a process when running in user mode. 729 * Arrange to reschedule if the resulting priority is better 730 * than that of the current process. 731 * 732 * This routine may be called with any process. 733 * 734 * This routine is called by fork1() for initial setup with the process 735 * of the run queue, and also may be called normally with the process on or 736 * off the run queue. 737 * 738 * MPSAFE 739 */ 740 static void 741 bsd4_resetpriority(struct lwp *lp) 742 { 743 bsd4_pcpu_t dd; 744 int newpriority; 745 u_short newrqtype; 746 int reschedcpu; 747 748 /* 749 * Calculate the new priority and queue type 750 */ 751 crit_enter(); 752 spin_lock_wr(&bsd4_spin); 753 754 newrqtype = lp->lwp_rtprio.type; 755 756 switch(newrqtype) { 757 case RTP_PRIO_REALTIME: 758 case RTP_PRIO_FIFO: 759 newpriority = PRIBASE_REALTIME + 760 (lp->lwp_rtprio.prio & PRIMASK); 761 break; 762 case RTP_PRIO_NORMAL: 763 newpriority = (lp->lwp_proc->p_nice - PRIO_MIN) * PPQ / NICEPPQ; 764 newpriority += lp->lwp_estcpu * PPQ / ESTCPUPPQ; 765 newpriority = newpriority * MAXPRI / (PRIO_RANGE * PPQ / 766 NICEPPQ + ESTCPUMAX * PPQ / ESTCPUPPQ); 767 newpriority = PRIBASE_NORMAL + (newpriority & PRIMASK); 768 break; 769 case RTP_PRIO_IDLE: 770 newpriority = PRIBASE_IDLE + (lp->lwp_rtprio.prio & PRIMASK); 771 break; 772 case RTP_PRIO_THREAD: 773 newpriority = PRIBASE_THREAD + (lp->lwp_rtprio.prio & PRIMASK); 774 break; 775 default: 776 panic("Bad RTP_PRIO %d", newrqtype); 777 /* NOT REACHED */ 778 } 779 780 /* 781 * The newpriority incorporates the queue type so do a simple masked 782 * check to determine if the process has moved to another queue. If 783 * it has, and it is currently on a run queue, then move it. 784 */ 785 if ((lp->lwp_priority ^ newpriority) & ~PPQMASK) { 786 lp->lwp_priority = newpriority; 787 if (lp->lwp_proc->p_flag & P_ONRUNQ) { 788 bsd4_remrunqueue_locked(lp); 789 lp->lwp_rqtype = newrqtype; 790 lp->lwp_rqindex = (newpriority & PRIMASK) / PPQ; 791 bsd4_setrunqueue_locked(lp); 792 reschedcpu = lp->lwp_thread->td_gd->gd_cpuid; 793 } else { 794 lp->lwp_rqtype = newrqtype; 795 lp->lwp_rqindex = (newpriority & PRIMASK) / PPQ; 796 reschedcpu = -1; 797 } 798 } else { 799 lp->lwp_priority = newpriority; 800 reschedcpu = -1; 801 } 802 spin_unlock_wr(&bsd4_spin); 803 804 /* 805 * Determine if we need to reschedule the target cpu. This only 806 * occurs if the LWP is already on a scheduler queue, which means 807 * that idle cpu notification has already occured. At most we 808 * need only issue a need_user_resched() on the appropriate cpu. 809 */ 810 if (reschedcpu >= 0) { 811 dd = &bsd4_pcpu[reschedcpu]; 812 KKASSERT(dd->uschedcp != lp); 813 if ((dd->upri & ~PRIMASK) > (lp->lwp_priority & ~PRIMASK)) { 814 dd->upri = lp->lwp_priority; 815 #ifdef SMP 816 if (reschedcpu == mycpu->gd_cpuid) { 817 need_user_resched(); 818 } else { 819 lwkt_send_ipiq(lp->lwp_thread->td_gd, 820 need_user_resched_remote, NULL); 821 } 822 #else 823 need_user_resched(); 824 #endif 825 } 826 } 827 crit_exit(); 828 } 829 830 /* 831 * Called from fork1() when a new child process is being created. 832 * 833 * Give the child process an initial estcpu that is more batch then 834 * its parent and dock the parent for the fork (but do not 835 * reschedule the parent). This comprises the main part of our batch 836 * detection heuristic for both parallel forking and sequential execs. 837 * 838 * Interactive processes will decay the boosted estcpu quickly while batch 839 * processes will tend to compound it. 840 * XXX lwp should be "spawning" instead of "forking" 841 * 842 * MPSAFE 843 */ 844 static void 845 bsd4_forking(struct lwp *plp, struct lwp *lp) 846 { 847 lp->lwp_estcpu = ESTCPULIM(plp->lwp_estcpu + ESTCPUPPQ); 848 lp->lwp_origcpu = lp->lwp_estcpu; 849 plp->lwp_estcpu = ESTCPULIM(plp->lwp_estcpu + ESTCPUPPQ); 850 } 851 852 /* 853 * Called when the parent reaps a child. Propogate cpu use by the child 854 * back to the parent. 855 * 856 * MPSAFE 857 */ 858 static void 859 bsd4_exiting(struct lwp *plp, struct lwp *lp) 860 { 861 int delta; 862 863 if (plp->lwp_proc->p_pid != 1) { 864 delta = lp->lwp_estcpu - lp->lwp_origcpu; 865 if (delta > 0) 866 plp->lwp_estcpu = ESTCPULIM(plp->lwp_estcpu + delta); 867 } 868 } 869 870 871 /* 872 * chooseproc() is called when a cpu needs a user process to LWKT schedule, 873 * it selects a user process and returns it. If chklp is non-NULL and chklp 874 * has a better or equal priority then the process that would otherwise be 875 * chosen, NULL is returned. 876 * 877 * Until we fix the RUNQ code the chklp test has to be strict or we may 878 * bounce between processes trying to acquire the current process designation. 879 * 880 * MPSAFE - must be called with bsd4_spin exclusive held. The spinlock is 881 * left intact through the entire routine. 882 */ 883 static 884 struct lwp * 885 chooseproc_locked(struct lwp *chklp) 886 { 887 struct lwp *lp; 888 struct rq *q; 889 u_int32_t *which, *which2; 890 u_int32_t pri; 891 u_int32_t rtqbits; 892 u_int32_t tsqbits; 893 u_int32_t idqbits; 894 cpumask_t cpumask; 895 896 rtqbits = bsd4_rtqueuebits; 897 tsqbits = bsd4_queuebits; 898 idqbits = bsd4_idqueuebits; 899 cpumask = mycpu->gd_cpumask; 900 901 #ifdef SMP 902 again: 903 #endif 904 if (rtqbits) { 905 pri = bsfl(rtqbits); 906 q = &bsd4_rtqueues[pri]; 907 which = &bsd4_rtqueuebits; 908 which2 = &rtqbits; 909 } else if (tsqbits) { 910 pri = bsfl(tsqbits); 911 q = &bsd4_queues[pri]; 912 which = &bsd4_queuebits; 913 which2 = &tsqbits; 914 } else if (idqbits) { 915 pri = bsfl(idqbits); 916 q = &bsd4_idqueues[pri]; 917 which = &bsd4_idqueuebits; 918 which2 = &idqbits; 919 } else { 920 return NULL; 921 } 922 lp = TAILQ_FIRST(q); 923 KASSERT(lp, ("chooseproc: no lwp on busy queue")); 924 925 #ifdef SMP 926 while ((lp->lwp_cpumask & cpumask) == 0) { 927 lp = TAILQ_NEXT(lp, lwp_procq); 928 if (lp == NULL) { 929 *which2 &= ~(1 << pri); 930 goto again; 931 } 932 } 933 #endif 934 935 /* 936 * If the passed lwp <chklp> is reasonably close to the selected 937 * lwp <lp>, return NULL (indicating that <chklp> should be kept). 938 * 939 * Note that we must error on the side of <chklp> to avoid bouncing 940 * between threads in the acquire code. 941 */ 942 if (chklp) { 943 if (chklp->lwp_priority < lp->lwp_priority + PPQ) 944 return(NULL); 945 } 946 947 #ifdef SMP 948 /* 949 * If the chosen lwp does not reside on this cpu spend a few 950 * cycles looking for a better candidate at the same priority level. 951 * This is a fallback check, setrunqueue() tries to wakeup the 952 * correct cpu and is our front-line affinity. 953 */ 954 if (lp->lwp_thread->td_gd != mycpu && 955 (chklp = TAILQ_NEXT(lp, lwp_procq)) != NULL 956 ) { 957 if (chklp->lwp_thread->td_gd == mycpu) { 958 ++choose_affinity; 959 lp = chklp; 960 } 961 } 962 #endif 963 964 TAILQ_REMOVE(q, lp, lwp_procq); 965 --bsd4_runqcount; 966 if (TAILQ_EMPTY(q)) 967 *which &= ~(1 << pri); 968 KASSERT((lp->lwp_proc->p_flag & P_ONRUNQ) != 0, ("not on runq6!")); 969 lp->lwp_proc->p_flag &= ~P_ONRUNQ; 970 return lp; 971 } 972 973 #ifdef SMP 974 /* 975 * Called via an ipi message to reschedule on another cpu. 976 * 977 * MPSAFE 978 */ 979 static 980 void 981 need_user_resched_remote(void *dummy) 982 { 983 need_user_resched(); 984 } 985 986 #endif 987 988 989 /* 990 * bsd4_remrunqueue_locked() removes a given process from the run queue 991 * that it is on, clearing the queue busy bit if it becomes empty. 992 * 993 * Note that user process scheduler is different from the LWKT schedule. 994 * The user process scheduler only manages user processes but it uses LWKT 995 * underneath, and a user process operating in the kernel will often be 996 * 'released' from our management. 997 * 998 * MPSAFE - bsd4_spin must be held exclusively on call 999 */ 1000 static void 1001 bsd4_remrunqueue_locked(struct lwp *lp) 1002 { 1003 struct rq *q; 1004 u_int32_t *which; 1005 u_int8_t pri; 1006 1007 KKASSERT(lp->lwp_proc->p_flag & P_ONRUNQ); 1008 lp->lwp_proc->p_flag &= ~P_ONRUNQ; 1009 --bsd4_runqcount; 1010 KKASSERT(bsd4_runqcount >= 0); 1011 1012 pri = lp->lwp_rqindex; 1013 switch(lp->lwp_rqtype) { 1014 case RTP_PRIO_NORMAL: 1015 q = &bsd4_queues[pri]; 1016 which = &bsd4_queuebits; 1017 break; 1018 case RTP_PRIO_REALTIME: 1019 case RTP_PRIO_FIFO: 1020 q = &bsd4_rtqueues[pri]; 1021 which = &bsd4_rtqueuebits; 1022 break; 1023 case RTP_PRIO_IDLE: 1024 q = &bsd4_idqueues[pri]; 1025 which = &bsd4_idqueuebits; 1026 break; 1027 default: 1028 panic("remrunqueue: invalid rtprio type"); 1029 /* NOT REACHED */ 1030 } 1031 TAILQ_REMOVE(q, lp, lwp_procq); 1032 if (TAILQ_EMPTY(q)) { 1033 KASSERT((*which & (1 << pri)) != 0, 1034 ("remrunqueue: remove from empty queue")); 1035 *which &= ~(1 << pri); 1036 } 1037 } 1038 1039 /* 1040 * bsd4_setrunqueue_locked() 1041 * 1042 * Add a process whos rqtype and rqindex had previously been calculated 1043 * onto the appropriate run queue. Determine if the addition requires 1044 * a reschedule on a cpu and return the cpuid or -1. 1045 * 1046 * NOTE: Lower priorities are better priorities. 1047 * 1048 * MPSAFE - bsd4_spin must be held exclusively on call 1049 */ 1050 static void 1051 bsd4_setrunqueue_locked(struct lwp *lp) 1052 { 1053 struct rq *q; 1054 u_int32_t *which; 1055 int pri; 1056 1057 KKASSERT((lp->lwp_proc->p_flag & P_ONRUNQ) == 0); 1058 lp->lwp_proc->p_flag |= P_ONRUNQ; 1059 ++bsd4_runqcount; 1060 1061 pri = lp->lwp_rqindex; 1062 1063 switch(lp->lwp_rqtype) { 1064 case RTP_PRIO_NORMAL: 1065 q = &bsd4_queues[pri]; 1066 which = &bsd4_queuebits; 1067 break; 1068 case RTP_PRIO_REALTIME: 1069 case RTP_PRIO_FIFO: 1070 q = &bsd4_rtqueues[pri]; 1071 which = &bsd4_rtqueuebits; 1072 break; 1073 case RTP_PRIO_IDLE: 1074 q = &bsd4_idqueues[pri]; 1075 which = &bsd4_idqueuebits; 1076 break; 1077 default: 1078 panic("remrunqueue: invalid rtprio type"); 1079 /* NOT REACHED */ 1080 } 1081 1082 /* 1083 * Add to the correct queue and set the appropriate bit. If no 1084 * lower priority (i.e. better) processes are in the queue then 1085 * we want a reschedule, calculate the best cpu for the job. 1086 * 1087 * Always run reschedules on the LWPs original cpu. 1088 */ 1089 TAILQ_INSERT_TAIL(q, lp, lwp_procq); 1090 *which |= 1 << pri; 1091 } 1092 1093 #ifdef SMP 1094 1095 /* 1096 * For SMP systems a user scheduler helper thread is created for each 1097 * cpu and is used to allow one cpu to wakeup another for the purposes of 1098 * scheduling userland threads from setrunqueue(). UP systems do not 1099 * need the helper since there is only one cpu. We can't use the idle 1100 * thread for this because we need to hold the MP lock. Additionally, 1101 * doing things this way allows us to HLT idle cpus on MP systems. 1102 * 1103 * MPSAFE 1104 */ 1105 static void 1106 sched_thread(void *dummy) 1107 { 1108 globaldata_t gd; 1109 bsd4_pcpu_t dd; 1110 struct lwp *nlp; 1111 cpumask_t cpumask; 1112 cpumask_t tmpmask; 1113 int cpuid; 1114 int tmpid; 1115 1116 gd = mycpu; 1117 cpuid = gd->gd_cpuid; /* doesn't change */ 1118 cpumask = 1 << cpuid; /* doesn't change */ 1119 dd = &bsd4_pcpu[cpuid]; 1120 1121 /* 1122 * The scheduler thread does not need to hold the MP lock. Since we 1123 * are woken up only when no user processes are scheduled on a cpu, we 1124 * can run at an ultra low priority. 1125 */ 1126 rel_mplock(); 1127 lwkt_setpri_self(TDPRI_USER_SCHEDULER); 1128 1129 for (;;) { 1130 /* 1131 * We use the LWKT deschedule-interlock trick to avoid racing 1132 * bsd4_rdyprocmask. This means we cannot block through to the 1133 * manual lwkt_switch() call we make below. 1134 */ 1135 crit_enter_gd(gd); 1136 lwkt_deschedule_self(gd->gd_curthread); 1137 spin_lock_wr(&bsd4_spin); 1138 atomic_set_int(&bsd4_rdyprocmask, cpumask); 1139 if ((bsd4_curprocmask & cpumask) == 0) { 1140 if ((nlp = chooseproc_locked(NULL)) != NULL) { 1141 atomic_set_int(&bsd4_curprocmask, cpumask); 1142 dd->upri = nlp->lwp_priority; 1143 dd->uschedcp = nlp; 1144 spin_unlock_wr(&bsd4_spin); 1145 lwkt_acquire(nlp->lwp_thread); 1146 lwkt_schedule(nlp->lwp_thread); 1147 } else { 1148 spin_unlock_wr(&bsd4_spin); 1149 } 1150 } else { 1151 /* 1152 * Someone scheduled us but raced. In order to not lose 1153 * track of the fact that there may be a LWP ready to go, 1154 * forward the request to another cpu if available. 1155 * 1156 * Rotate through cpus starting with cpuid + 1. Since cpuid 1157 * is already masked out by gd_other_cpus, just use ~cpumask. 1158 */ 1159 tmpmask = ~bsd4_curprocmask & bsd4_rdyprocmask & 1160 mycpu->gd_other_cpus; 1161 if (tmpmask) { 1162 if (tmpmask & ~(cpumask - 1)) 1163 tmpid = bsfl(tmpmask & ~(cpumask - 1)); 1164 else 1165 tmpid = bsfl(tmpmask); 1166 bsd4_scancpu = tmpid; 1167 atomic_clear_int(&bsd4_rdyprocmask, 1 << tmpid); 1168 spin_unlock_wr(&bsd4_spin); 1169 lwkt_schedule(&bsd4_pcpu[tmpid].helper_thread); 1170 } else { 1171 spin_unlock_wr(&bsd4_spin); 1172 } 1173 } 1174 crit_exit_gd(gd); 1175 lwkt_switch(); 1176 } 1177 } 1178 1179 /* 1180 * Setup our scheduler helpers. Note that curprocmask bit 0 has already 1181 * been cleared by rqinit() and we should not mess with it further. 1182 */ 1183 static void 1184 sched_thread_cpu_init(void) 1185 { 1186 int i; 1187 1188 if (bootverbose) 1189 printf("start scheduler helpers on cpus:"); 1190 1191 for (i = 0; i < ncpus; ++i) { 1192 bsd4_pcpu_t dd = &bsd4_pcpu[i]; 1193 cpumask_t mask = 1 << i; 1194 1195 if ((mask & smp_active_mask) == 0) 1196 continue; 1197 1198 if (bootverbose) 1199 printf(" %d", i); 1200 1201 lwkt_create(sched_thread, NULL, NULL, &dd->helper_thread, 1202 TDF_STOPREQ, i, "usched %d", i); 1203 1204 /* 1205 * Allow user scheduling on the target cpu. cpu #0 has already 1206 * been enabled in rqinit(). 1207 */ 1208 if (i) 1209 atomic_clear_int(&bsd4_curprocmask, mask); 1210 atomic_set_int(&bsd4_rdyprocmask, mask); 1211 } 1212 if (bootverbose) 1213 printf("\n"); 1214 } 1215 SYSINIT(uschedtd, SI_SUB_FINISH_SMP, SI_ORDER_ANY, sched_thread_cpu_init, NULL) 1216 1217 #endif 1218 1219