1 /*-
2 * CAM IO Scheduler Interface
3 *
4 * SPDX-License-Identifier: BSD-2-Clause
5 *
6 * Copyright (c) 2015 Netflix, Inc.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following 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 AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #include "opt_ddb.h"
31
32 #include <sys/param.h>
33 #include <sys/systm.h>
34 #include <sys/kernel.h>
35 #include <sys/bio.h>
36 #include <sys/lock.h>
37 #include <sys/malloc.h>
38 #include <sys/mutex.h>
39 #include <sys/sbuf.h>
40 #include <sys/sysctl.h>
41
42 #include <cam/cam.h>
43 #include <cam/cam_ccb.h>
44 #include <cam/cam_periph.h>
45 #include <cam/cam_xpt_periph.h>
46 #include <cam/cam_xpt_internal.h>
47 #include <cam/cam_iosched.h>
48
49 #include <ddb/ddb.h>
50
51 static MALLOC_DEFINE(M_CAMSCHED, "CAM I/O Scheduler",
52 "CAM I/O Scheduler buffers");
53
54 static SYSCTL_NODE(_kern_cam, OID_AUTO, iosched, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
55 "CAM I/O Scheduler parameters");
56
57 /*
58 * Default I/O scheduler for FreeBSD. This implementation is just a thin-vineer
59 * over the bioq_* interface, with notions of separate calls for normal I/O and
60 * for trims.
61 *
62 * When CAM_IOSCHED_DYNAMIC is defined, the scheduler is enhanced to dynamically
63 * steer the rate of one type of traffic to help other types of traffic (eg
64 * limit writes when read latency deteriorates on SSDs).
65 */
66
67 #ifdef CAM_IOSCHED_DYNAMIC
68
69 static bool do_dynamic_iosched = true;
70 SYSCTL_BOOL(_kern_cam_iosched, OID_AUTO, dynamic, CTLFLAG_RDTUN,
71 &do_dynamic_iosched, 1,
72 "Enable Dynamic I/O scheduler optimizations.");
73
74 /*
75 * For an EMA, with an alpha of alpha, we know
76 * alpha = 2 / (N + 1)
77 * or
78 * N = 1 + (2 / alpha)
79 * where N is the number of samples that 86% of the current
80 * EMA is derived from.
81 *
82 * So we invent[*] alpha_bits:
83 * alpha_bits = -log_2(alpha)
84 * alpha = 2^-alpha_bits
85 * So
86 * N = 1 + 2^(alpha_bits + 1)
87 *
88 * The default 9 gives a 1025 lookback for 86% of the data.
89 * For a brief intro: https://en.wikipedia.org/wiki/Moving_average
90 *
91 * [*] Steal from the load average code and many other places.
92 * Note: See computation of EMA and EMVAR for acceptable ranges of alpha.
93 */
94 static int alpha_bits = 9;
95 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, alpha_bits, CTLFLAG_RWTUN,
96 &alpha_bits, 1,
97 "Bits in EMA's alpha.");
98
99 /*
100 * Different parameters for the buckets of latency we keep track of. These are all
101 * published read-only since at present they are compile time constants.
102 *
103 * Bucket base is the upper bounds of the first latency bucket. It's currently 20us.
104 * With 20 buckets (see below), that leads to a geometric progression with a max size
105 * of 5.2s which is safeily larger than 1s to help diagnose extreme outliers better.
106 */
107 #ifndef BUCKET_BASE
108 #define BUCKET_BASE ((SBT_1S / 50000) + 1) /* 20us */
109 #endif
110 static sbintime_t bucket_base = BUCKET_BASE;
111 SYSCTL_SBINTIME_USEC(_kern_cam_iosched, OID_AUTO, bucket_base_us, CTLFLAG_RD,
112 &bucket_base,
113 "Size of the smallest latency bucket");
114
115 /*
116 * Bucket ratio is the geometric progression for the bucket. For a bucket b_n
117 * the size of bucket b_n+1 is b_n * bucket_ratio / 100.
118 */
119 static int bucket_ratio = 200; /* Rather hard coded at the moment */
120 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, bucket_ratio, CTLFLAG_RD,
121 &bucket_ratio, 200,
122 "Latency Bucket Ratio for geometric progression.");
123
124 /*
125 * Number of total buckets. Starting at BUCKET_BASE, each one is a power of 2.
126 */
127 #ifndef LAT_BUCKETS
128 #define LAT_BUCKETS 20 /* < 20us < 40us ... < 2^(n-1)*20us >= 2^(n-1)*20us */
129 #endif
130 static int lat_buckets = LAT_BUCKETS;
131 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, buckets, CTLFLAG_RD,
132 &lat_buckets, LAT_BUCKETS,
133 "Total number of latency buckets published");
134
135 /*
136 * Read bias: how many reads do we favor before scheduling a write
137 * when we have a choice.
138 */
139 static int default_read_bias = 0;
140 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, read_bias, CTLFLAG_RWTUN,
141 &default_read_bias, 0,
142 "Default read bias for new devices.");
143
144 struct iop_stats;
145 struct cam_iosched_softc;
146
147 int iosched_debug = 0;
148
149 typedef enum {
150 none = 0, /* No limits */
151 queue_depth, /* Limit how many ops we queue to SIM */
152 iops, /* Limit # of IOPS to the drive */
153 bandwidth, /* Limit bandwidth to the drive */
154 limiter_max
155 } io_limiter;
156
157 static const char *cam_iosched_limiter_names[] =
158 { "none", "queue_depth", "iops", "bandwidth" };
159
160 /*
161 * Called to initialize the bits of the iop_stats structure relevant to the
162 * limiter. Called just after the limiter is set.
163 */
164 typedef int l_init_t(struct iop_stats *);
165
166 /*
167 * Called every tick.
168 */
169 typedef int l_tick_t(struct iop_stats *);
170
171 /*
172 * Called to see if the limiter thinks this IOP can be allowed to
173 * proceed. If so, the limiter assumes that the IOP proceeded
174 * and makes any accounting of it that's needed.
175 */
176 typedef int l_iop_t(struct iop_stats *, struct bio *);
177
178 /*
179 * Called when an I/O completes so the limiter can update its
180 * accounting. Pending I/Os may complete in any order (even when
181 * sent to the hardware at the same time), so the limiter may not
182 * make any assumptions other than this I/O has completed. If it
183 * returns 1, then xpt_schedule() needs to be called again.
184 */
185 typedef int l_iodone_t(struct iop_stats *, struct bio *);
186
187 static l_iop_t cam_iosched_qd_iop;
188 static l_iop_t cam_iosched_qd_caniop;
189 static l_iodone_t cam_iosched_qd_iodone;
190
191 static l_init_t cam_iosched_iops_init;
192 static l_tick_t cam_iosched_iops_tick;
193 static l_iop_t cam_iosched_iops_caniop;
194 static l_iop_t cam_iosched_iops_iop;
195
196 static l_init_t cam_iosched_bw_init;
197 static l_tick_t cam_iosched_bw_tick;
198 static l_iop_t cam_iosched_bw_caniop;
199 static l_iop_t cam_iosched_bw_iop;
200
201 struct limswitch {
202 l_init_t *l_init;
203 l_tick_t *l_tick;
204 l_iop_t *l_iop;
205 l_iop_t *l_caniop;
206 l_iodone_t *l_iodone;
207 } limsw[] =
208 {
209 { /* none */
210 .l_init = NULL,
211 .l_tick = NULL,
212 .l_iop = NULL,
213 .l_iodone= NULL,
214 },
215 { /* queue_depth */
216 .l_init = NULL,
217 .l_tick = NULL,
218 .l_caniop = cam_iosched_qd_caniop,
219 .l_iop = cam_iosched_qd_iop,
220 .l_iodone= cam_iosched_qd_iodone,
221 },
222 { /* iops */
223 .l_init = cam_iosched_iops_init,
224 .l_tick = cam_iosched_iops_tick,
225 .l_caniop = cam_iosched_iops_caniop,
226 .l_iop = cam_iosched_iops_iop,
227 .l_iodone= NULL,
228 },
229 { /* bandwidth */
230 .l_init = cam_iosched_bw_init,
231 .l_tick = cam_iosched_bw_tick,
232 .l_caniop = cam_iosched_bw_caniop,
233 .l_iop = cam_iosched_bw_iop,
234 .l_iodone= NULL,
235 },
236 };
237
238 struct iop_stats {
239 /*
240 * sysctl state for this subnode.
241 */
242 struct sysctl_ctx_list sysctl_ctx;
243 struct sysctl_oid *sysctl_tree;
244
245 /*
246 * Information about the current rate limiters, if any
247 */
248 io_limiter limiter; /* How are I/Os being limited */
249 int min; /* Low range of limit */
250 int max; /* High range of limit */
251 int current; /* Current rate limiter */
252 int l_value1; /* per-limiter scratch value 1. */
253 int l_value2; /* per-limiter scratch value 2. */
254
255 /*
256 * Debug information about counts of I/Os that have gone through the
257 * scheduler.
258 */
259 int pending; /* I/Os pending in the hardware */
260 int queued; /* number currently in the queue */
261 int total; /* Total for all time -- wraps */
262 int in; /* number queued all time -- wraps */
263 int out; /* number completed all time -- wraps */
264 int errs; /* Number of I/Os completed with error -- wraps */
265
266 /*
267 * Statistics on different bits of the process.
268 */
269 /* Exp Moving Average, see alpha_bits for more details */
270 sbintime_t ema;
271 sbintime_t emvar;
272 sbintime_t sd; /* Last computed sd */
273
274 uint32_t state_flags;
275 #define IOP_RATE_LIMITED 1u
276
277 uint64_t latencies[LAT_BUCKETS];
278
279 struct cam_iosched_softc *softc;
280 };
281
282 typedef enum {
283 set_max = 0, /* current = max */
284 read_latency, /* Steer read latency by throttling writes */
285 cl_max /* Keep last */
286 } control_type;
287
288 static const char *cam_iosched_control_type_names[] =
289 { "set_max", "read_latency" };
290
291 struct control_loop {
292 /*
293 * sysctl state for this subnode.
294 */
295 struct sysctl_ctx_list sysctl_ctx;
296 struct sysctl_oid *sysctl_tree;
297
298 sbintime_t next_steer; /* Time of next steer */
299 sbintime_t steer_interval; /* How often do we steer? */
300 sbintime_t lolat;
301 sbintime_t hilat;
302 int alpha;
303 control_type type; /* What type of control? */
304 int last_count; /* Last I/O count */
305
306 struct cam_iosched_softc *softc;
307 };
308
309 #endif
310
311 struct cam_iosched_softc {
312 struct bio_queue_head bio_queue;
313 struct bio_queue_head trim_queue;
314 /* scheduler flags < 16, user flags >= 16 */
315 uint32_t flags;
316 int sort_io_queue;
317 int trim_goal; /* # of trims to queue before sending */
318 int trim_ticks; /* Max ticks to hold trims */
319 int last_trim_tick; /* Last 'tick' time ld a trim */
320 int queued_trims; /* Number of trims in the queue */
321 #ifdef CAM_IOSCHED_DYNAMIC
322 int read_bias; /* Read bias setting */
323 int current_read_bias; /* Current read bias state */
324 int total_ticks;
325 int load; /* EMA of 'load average' of disk / 2^16 */
326
327 struct bio_queue_head write_queue;
328 struct iop_stats read_stats, write_stats, trim_stats;
329 struct sysctl_ctx_list sysctl_ctx;
330 struct sysctl_oid *sysctl_tree;
331
332 int quanta; /* Number of quanta per second */
333 struct callout ticker; /* Callout for our quota system */
334 struct cam_periph *periph; /* cam periph associated with this device */
335 uint32_t this_frac; /* Fraction of a second (1024ths) for this tick */
336 sbintime_t last_time; /* Last time we ticked */
337 struct control_loop cl;
338 sbintime_t max_lat; /* when != 0, if iop latency > max_lat, call max_lat_fcn */
339 cam_iosched_latfcn_t latfcn;
340 void *latarg;
341 #endif
342 };
343
344 #ifdef CAM_IOSCHED_DYNAMIC
345 /*
346 * helper functions to call the limsw functions.
347 */
348 static int
cam_iosched_limiter_init(struct iop_stats * ios)349 cam_iosched_limiter_init(struct iop_stats *ios)
350 {
351 int lim = ios->limiter;
352
353 /* maybe this should be a kassert */
354 if (lim < none || lim >= limiter_max)
355 return EINVAL;
356
357 if (limsw[lim].l_init)
358 return limsw[lim].l_init(ios);
359
360 return 0;
361 }
362
363 static int
cam_iosched_limiter_tick(struct iop_stats * ios)364 cam_iosched_limiter_tick(struct iop_stats *ios)
365 {
366 int lim = ios->limiter;
367
368 /* maybe this should be a kassert */
369 if (lim < none || lim >= limiter_max)
370 return EINVAL;
371
372 if (limsw[lim].l_tick)
373 return limsw[lim].l_tick(ios);
374
375 return 0;
376 }
377
378 static int
cam_iosched_limiter_iop(struct iop_stats * ios,struct bio * bp)379 cam_iosched_limiter_iop(struct iop_stats *ios, struct bio *bp)
380 {
381 int lim = ios->limiter;
382
383 /* maybe this should be a kassert */
384 if (lim < none || lim >= limiter_max)
385 return EINVAL;
386
387 if (limsw[lim].l_iop)
388 return limsw[lim].l_iop(ios, bp);
389
390 return 0;
391 }
392
393 static int
cam_iosched_limiter_caniop(struct iop_stats * ios,struct bio * bp)394 cam_iosched_limiter_caniop(struct iop_stats *ios, struct bio *bp)
395 {
396 int lim = ios->limiter;
397
398 /* maybe this should be a kassert */
399 if (lim < none || lim >= limiter_max)
400 return EINVAL;
401
402 if (limsw[lim].l_caniop)
403 return limsw[lim].l_caniop(ios, bp);
404
405 return 0;
406 }
407
408 static int
cam_iosched_limiter_iodone(struct iop_stats * ios,struct bio * bp)409 cam_iosched_limiter_iodone(struct iop_stats *ios, struct bio *bp)
410 {
411 int lim = ios->limiter;
412
413 /* maybe this should be a kassert */
414 if (lim < none || lim >= limiter_max)
415 return 0;
416
417 if (limsw[lim].l_iodone)
418 return limsw[lim].l_iodone(ios, bp);
419
420 return 0;
421 }
422
423 /*
424 * Functions to implement the different kinds of limiters
425 */
426
427 static int
cam_iosched_qd_iop(struct iop_stats * ios,struct bio * bp)428 cam_iosched_qd_iop(struct iop_stats *ios, struct bio *bp)
429 {
430
431 if (ios->current <= 0 || ios->pending < ios->current)
432 return 0;
433
434 return EAGAIN;
435 }
436
437 static int
cam_iosched_qd_caniop(struct iop_stats * ios,struct bio * bp)438 cam_iosched_qd_caniop(struct iop_stats *ios, struct bio *bp)
439 {
440
441 if (ios->current <= 0 || ios->pending < ios->current)
442 return 0;
443
444 return EAGAIN;
445 }
446
447 static int
cam_iosched_qd_iodone(struct iop_stats * ios,struct bio * bp)448 cam_iosched_qd_iodone(struct iop_stats *ios, struct bio *bp)
449 {
450
451 if (ios->current <= 0 || ios->pending != ios->current)
452 return 0;
453
454 return 1;
455 }
456
457 static int
cam_iosched_iops_init(struct iop_stats * ios)458 cam_iosched_iops_init(struct iop_stats *ios)
459 {
460
461 ios->l_value1 = ios->current / ios->softc->quanta;
462 if (ios->l_value1 <= 0)
463 ios->l_value1 = 1;
464 ios->l_value2 = 0;
465
466 return 0;
467 }
468
469 static int
cam_iosched_iops_tick(struct iop_stats * ios)470 cam_iosched_iops_tick(struct iop_stats *ios)
471 {
472 int new_ios;
473
474 /*
475 * Allow at least one IO per tick until all
476 * the IOs for this interval have been spent.
477 */
478 new_ios = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16);
479 if (new_ios < 1 && ios->l_value2 < ios->current) {
480 new_ios = 1;
481 ios->l_value2++;
482 }
483
484 /*
485 * If this a new accounting interval, discard any "unspent" ios
486 * granted in the previous interval. Otherwise add the new ios to
487 * the previously granted ones that haven't been spent yet.
488 */
489 if ((ios->softc->total_ticks % ios->softc->quanta) == 0) {
490 ios->l_value1 = new_ios;
491 ios->l_value2 = 1;
492 } else {
493 ios->l_value1 += new_ios;
494 }
495
496 return 0;
497 }
498
499 static int
cam_iosched_iops_caniop(struct iop_stats * ios,struct bio * bp)500 cam_iosched_iops_caniop(struct iop_stats *ios, struct bio *bp)
501 {
502
503 /*
504 * So if we have any more IOPs left, allow it,
505 * otherwise wait. If current iops is 0, treat that
506 * as unlimited as a failsafe.
507 */
508 if (ios->current > 0 && ios->l_value1 <= 0)
509 return EAGAIN;
510 return 0;
511 }
512
513 static int
cam_iosched_iops_iop(struct iop_stats * ios,struct bio * bp)514 cam_iosched_iops_iop(struct iop_stats *ios, struct bio *bp)
515 {
516 int rv;
517
518 rv = cam_iosched_limiter_caniop(ios, bp);
519 if (rv == 0)
520 ios->l_value1--;
521
522 return rv;
523 }
524
525 static int
cam_iosched_bw_init(struct iop_stats * ios)526 cam_iosched_bw_init(struct iop_stats *ios)
527 {
528
529 /* ios->current is in kB/s, so scale to bytes */
530 ios->l_value1 = ios->current * 1000 / ios->softc->quanta;
531
532 return 0;
533 }
534
535 static int
cam_iosched_bw_tick(struct iop_stats * ios)536 cam_iosched_bw_tick(struct iop_stats *ios)
537 {
538 int bw;
539
540 /*
541 * If we're in the hole for available quota from
542 * the last time, then add the quantum for this.
543 * If we have any left over from last quantum,
544 * then too bad, that's lost. Also, ios->current
545 * is in kB/s, so scale.
546 *
547 * We also allow up to 4 quanta of credits to
548 * accumulate to deal with burstiness. 4 is extremely
549 * arbitrary.
550 */
551 bw = (int)((ios->current * 1000ull * (uint64_t)ios->softc->this_frac) >> 16);
552 if (ios->l_value1 < bw * 4)
553 ios->l_value1 += bw;
554
555 return 0;
556 }
557
558 static int
cam_iosched_bw_caniop(struct iop_stats * ios,struct bio * bp)559 cam_iosched_bw_caniop(struct iop_stats *ios, struct bio *bp)
560 {
561 /*
562 * So if we have any more bw quota left, allow it,
563 * otherwise wait. Note, we'll go negative and that's
564 * OK. We'll just get a little less next quota.
565 *
566 * Note on going negative: that allows us to process
567 * requests in order better, since we won't allow
568 * shorter reads to get around the long one that we
569 * don't have the quota to do just yet. It also prevents
570 * starvation by being a little more permissive about
571 * what we let through this quantum (to prevent the
572 * starvation), at the cost of getting a little less
573 * next quantum.
574 *
575 * Also note that if the current limit is <= 0,
576 * we treat it as unlimited as a failsafe.
577 */
578 if (ios->current > 0 && ios->l_value1 <= 0)
579 return EAGAIN;
580
581 return 0;
582 }
583
584 static int
cam_iosched_bw_iop(struct iop_stats * ios,struct bio * bp)585 cam_iosched_bw_iop(struct iop_stats *ios, struct bio *bp)
586 {
587 int rv;
588
589 rv = cam_iosched_limiter_caniop(ios, bp);
590 if (rv == 0)
591 ios->l_value1 -= bp->bio_length;
592
593 return rv;
594 }
595
596 static void cam_iosched_cl_maybe_steer(struct control_loop *clp);
597
598 static void
cam_iosched_ticker(void * arg)599 cam_iosched_ticker(void *arg)
600 {
601 struct cam_iosched_softc *isc = arg;
602 sbintime_t now, delta;
603 int pending;
604
605 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc);
606
607 now = sbinuptime();
608 delta = now - isc->last_time;
609 isc->this_frac = (uint32_t)delta >> 16; /* Note: discards seconds -- should be 0 harmless if not */
610 isc->last_time = now;
611
612 cam_iosched_cl_maybe_steer(&isc->cl);
613
614 cam_iosched_limiter_tick(&isc->read_stats);
615 cam_iosched_limiter_tick(&isc->write_stats);
616 cam_iosched_limiter_tick(&isc->trim_stats);
617
618 cam_iosched_schedule(isc, isc->periph);
619
620 /*
621 * isc->load is an EMA of the pending I/Os at each tick. The number of
622 * pending I/Os is the sum of the I/Os queued to the hardware, and those
623 * in the software queue that could be queued to the hardware if there
624 * were slots.
625 *
626 * ios_stats.pending is a count of requests in the SIM right now for
627 * each of these types of I/O. So the total pending count is the sum of
628 * these I/Os and the sum of the queued I/Os still in the software queue
629 * for those operations that aren't being rate limited at the moment.
630 *
631 * The reason for the rate limiting bit is because those I/Os
632 * aren't part of the software queued load (since we could
633 * give them to hardware, but choose not to).
634 *
635 * Note: due to a bug in counting pending TRIM in the device, we
636 * don't include them in this count. We count each BIO_DELETE in
637 * the pending count, but the periph drivers collapse them down
638 * into one TRIM command. That one trim command gets the completion
639 * so the counts get off.
640 */
641 pending = isc->read_stats.pending + isc->write_stats.pending /* + isc->trim_stats.pending */;
642 pending += !!(isc->read_stats.state_flags & IOP_RATE_LIMITED) * isc->read_stats.queued +
643 !!(isc->write_stats.state_flags & IOP_RATE_LIMITED) * isc->write_stats.queued /* +
644 !!(isc->trim_stats.state_flags & IOP_RATE_LIMITED) * isc->trim_stats.queued */ ;
645 pending <<= 16;
646 pending /= isc->periph->path->device->ccbq.total_openings;
647
648 isc->load = (pending + (isc->load << 13) - isc->load) >> 13; /* see above: 13 -> 16139 / 200/s = ~81s ~1 minute */
649
650 isc->total_ticks++;
651 }
652
653 static void
cam_iosched_cl_init(struct control_loop * clp,struct cam_iosched_softc * isc)654 cam_iosched_cl_init(struct control_loop *clp, struct cam_iosched_softc *isc)
655 {
656
657 clp->next_steer = sbinuptime();
658 clp->softc = isc;
659 clp->steer_interval = SBT_1S * 5; /* Let's start out steering every 5s */
660 clp->lolat = 5 * SBT_1MS;
661 clp->hilat = 15 * SBT_1MS;
662 clp->alpha = 20; /* Alpha == gain. 20 = .2 */
663 clp->type = set_max;
664 }
665
666 static void
cam_iosched_cl_maybe_steer(struct control_loop * clp)667 cam_iosched_cl_maybe_steer(struct control_loop *clp)
668 {
669 struct cam_iosched_softc *isc;
670 sbintime_t now, lat;
671 int old;
672
673 isc = clp->softc;
674 now = isc->last_time;
675 if (now < clp->next_steer)
676 return;
677
678 clp->next_steer = now + clp->steer_interval;
679 switch (clp->type) {
680 case set_max:
681 if (isc->write_stats.current != isc->write_stats.max)
682 printf("Steering write from %d kBps to %d kBps\n",
683 isc->write_stats.current, isc->write_stats.max);
684 isc->read_stats.current = isc->read_stats.max;
685 isc->write_stats.current = isc->write_stats.max;
686 isc->trim_stats.current = isc->trim_stats.max;
687 break;
688 case read_latency:
689 old = isc->write_stats.current;
690 lat = isc->read_stats.ema;
691 /*
692 * Simple PLL-like engine. Since we're steering to a range for
693 * the SP (set point) that makes things a little more
694 * complicated. In addition, we're not directly controlling our
695 * PV (process variable), the read latency, but instead are
696 * manipulating the write bandwidth limit for our MV
697 * (manipulation variable), analysis of this code gets a bit
698 * messy. Also, the MV is a very noisy control surface for read
699 * latency since it is affected by many hidden processes inside
700 * the device which change how responsive read latency will be
701 * in reaction to changes in write bandwidth. Unlike the classic
702 * boiler control PLL. this may result in over-steering while
703 * the SSD takes its time to react to the new, lower load. This
704 * is why we use a relatively low alpha of between .1 and .25 to
705 * compensate for this effect. At .1, it takes ~22 steering
706 * intervals to back off by a factor of 10. At .2 it only takes
707 * ~10. At .25 it only takes ~8. However some preliminary data
708 * from the SSD drives suggests a reasponse time in 10's of
709 * seconds before latency drops regardless of the new write
710 * rate. Careful observation will be required to tune this
711 * effectively.
712 *
713 * Also, when there's no read traffic, we jack up the write
714 * limit too regardless of the last read latency. 10 is
715 * somewhat arbitrary.
716 */
717 if (lat < clp->lolat || isc->read_stats.total - clp->last_count < 10)
718 isc->write_stats.current = isc->write_stats.current *
719 (100 + clp->alpha) / 100; /* Scale up */
720 else if (lat > clp->hilat)
721 isc->write_stats.current = isc->write_stats.current *
722 (100 - clp->alpha) / 100; /* Scale down */
723 clp->last_count = isc->read_stats.total;
724
725 /*
726 * Even if we don't steer, per se, enforce the min/max limits as
727 * those may have changed.
728 */
729 if (isc->write_stats.current < isc->write_stats.min)
730 isc->write_stats.current = isc->write_stats.min;
731 if (isc->write_stats.current > isc->write_stats.max)
732 isc->write_stats.current = isc->write_stats.max;
733 if (old != isc->write_stats.current && iosched_debug)
734 printf("Steering write from %d kBps to %d kBps due to latency of %jdus\n",
735 old, isc->write_stats.current,
736 (uintmax_t)((uint64_t)1000000 * (uint32_t)lat) >> 32);
737 break;
738 case cl_max:
739 break;
740 }
741 }
742 #endif
743
744 /*
745 * Trim or similar currently pending completion. Should only be set for
746 * those drivers wishing only one Trim active at a time.
747 */
748 #define CAM_IOSCHED_FLAG_TRIM_ACTIVE (1ul << 0)
749 /* Callout active, and needs to be torn down */
750 #define CAM_IOSCHED_FLAG_CALLOUT_ACTIVE (1ul << 1)
751
752 /* Periph drivers set these flags to indicate work */
753 #define CAM_IOSCHED_FLAG_WORK_FLAGS ((0xffffu) << 16)
754
755 #ifdef CAM_IOSCHED_DYNAMIC
756 static void
757 cam_iosched_io_metric_update(struct cam_iosched_softc *isc,
758 sbintime_t sim_latency, int cmd, size_t size);
759 #endif
760
761 static inline bool
cam_iosched_has_flagged_work(struct cam_iosched_softc * isc)762 cam_iosched_has_flagged_work(struct cam_iosched_softc *isc)
763 {
764 return !!(isc->flags & CAM_IOSCHED_FLAG_WORK_FLAGS);
765 }
766
767 static inline bool
cam_iosched_has_io(struct cam_iosched_softc * isc)768 cam_iosched_has_io(struct cam_iosched_softc *isc)
769 {
770 #ifdef CAM_IOSCHED_DYNAMIC
771 if (do_dynamic_iosched) {
772 struct bio *rbp = bioq_first(&isc->bio_queue);
773 struct bio *wbp = bioq_first(&isc->write_queue);
774 bool can_write = wbp != NULL &&
775 cam_iosched_limiter_caniop(&isc->write_stats, wbp) == 0;
776 bool can_read = rbp != NULL &&
777 cam_iosched_limiter_caniop(&isc->read_stats, rbp) == 0;
778 if (iosched_debug > 2) {
779 printf("can write %d: pending_writes %d max_writes %d\n", can_write, isc->write_stats.pending, isc->write_stats.max);
780 printf("can read %d: read_stats.pending %d max_reads %d\n", can_read, isc->read_stats.pending, isc->read_stats.max);
781 printf("Queued reads %d writes %d\n", isc->read_stats.queued, isc->write_stats.queued);
782 }
783 return can_read || can_write;
784 }
785 #endif
786 return bioq_first(&isc->bio_queue) != NULL;
787 }
788
789 static inline bool
cam_iosched_has_more_trim(struct cam_iosched_softc * isc)790 cam_iosched_has_more_trim(struct cam_iosched_softc *isc)
791 {
792 struct bio *bp;
793
794 bp = bioq_first(&isc->trim_queue);
795 #ifdef CAM_IOSCHED_DYNAMIC
796 if (do_dynamic_iosched) {
797 /*
798 * If we're limiting trims, then defer action on trims
799 * for a bit.
800 */
801 if (bp == NULL || cam_iosched_limiter_caniop(&isc->trim_stats, bp) != 0)
802 return false;
803 }
804 #endif
805
806 /*
807 * If we've set a trim_goal, then if we exceed that allow trims
808 * to be passed back to the driver. If we've also set a tick timeout
809 * allow trims back to the driver. Otherwise, don't allow trims yet.
810 */
811 if (isc->trim_goal > 0) {
812 if (isc->queued_trims >= isc->trim_goal)
813 return true;
814 if (isc->queued_trims > 0 &&
815 isc->trim_ticks > 0 &&
816 ticks - isc->last_trim_tick > isc->trim_ticks)
817 return true;
818 return false;
819 }
820
821 /* NB: Should perhaps have a max trim active independent of I/O limiters */
822 return !(isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) && bp != NULL;
823 }
824
825 #define cam_iosched_sort_queue(isc) ((isc)->sort_io_queue >= 0 ? \
826 (isc)->sort_io_queue : cam_sort_io_queues)
827
828 static inline bool
cam_iosched_has_work(struct cam_iosched_softc * isc)829 cam_iosched_has_work(struct cam_iosched_softc *isc)
830 {
831 #ifdef CAM_IOSCHED_DYNAMIC
832 if (iosched_debug > 2)
833 printf("has work: %d %d %d\n", cam_iosched_has_io(isc),
834 cam_iosched_has_more_trim(isc),
835 cam_iosched_has_flagged_work(isc));
836 #endif
837
838 return cam_iosched_has_io(isc) ||
839 cam_iosched_has_more_trim(isc) ||
840 cam_iosched_has_flagged_work(isc);
841 }
842
843 #ifdef CAM_IOSCHED_DYNAMIC
844 static void
cam_iosched_iop_stats_init(struct cam_iosched_softc * isc,struct iop_stats * ios)845 cam_iosched_iop_stats_init(struct cam_iosched_softc *isc, struct iop_stats *ios)
846 {
847
848 ios->limiter = none;
849 ios->in = 0;
850 ios->max = ios->current = 300000;
851 ios->min = 1;
852 ios->out = 0;
853 ios->errs = 0;
854 ios->pending = 0;
855 ios->queued = 0;
856 ios->total = 0;
857 ios->ema = 0;
858 ios->emvar = 0;
859 ios->softc = isc;
860 cam_iosched_limiter_init(ios);
861 }
862
863 static int
cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS)864 cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS)
865 {
866 char buf[16];
867 struct iop_stats *ios;
868 struct cam_iosched_softc *isc;
869 int value, i, error;
870 const char *p;
871
872 ios = arg1;
873 isc = ios->softc;
874 value = ios->limiter;
875 if (value < none || value >= limiter_max)
876 p = "UNKNOWN";
877 else
878 p = cam_iosched_limiter_names[value];
879
880 strlcpy(buf, p, sizeof(buf));
881 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
882 if (error != 0 || req->newptr == NULL)
883 return error;
884
885 cam_periph_lock(isc->periph);
886
887 for (i = none; i < limiter_max; i++) {
888 if (strcmp(buf, cam_iosched_limiter_names[i]) != 0)
889 continue;
890 ios->limiter = i;
891 error = cam_iosched_limiter_init(ios);
892 if (error != 0) {
893 ios->limiter = value;
894 cam_periph_unlock(isc->periph);
895 return error;
896 }
897 /* Note: disk load averate requires ticker to be always running */
898 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc);
899 isc->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
900
901 cam_periph_unlock(isc->periph);
902 return 0;
903 }
904
905 cam_periph_unlock(isc->periph);
906 return EINVAL;
907 }
908
909 static int
cam_iosched_control_type_sysctl(SYSCTL_HANDLER_ARGS)910 cam_iosched_control_type_sysctl(SYSCTL_HANDLER_ARGS)
911 {
912 char buf[16];
913 struct control_loop *clp;
914 struct cam_iosched_softc *isc;
915 int value, i, error;
916 const char *p;
917
918 clp = arg1;
919 isc = clp->softc;
920 value = clp->type;
921 if (value < none || value >= cl_max)
922 p = "UNKNOWN";
923 else
924 p = cam_iosched_control_type_names[value];
925
926 strlcpy(buf, p, sizeof(buf));
927 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
928 if (error != 0 || req->newptr == NULL)
929 return error;
930
931 for (i = set_max; i < cl_max; i++) {
932 if (strcmp(buf, cam_iosched_control_type_names[i]) != 0)
933 continue;
934 cam_periph_lock(isc->periph);
935 clp->type = i;
936 cam_periph_unlock(isc->periph);
937 return 0;
938 }
939
940 return EINVAL;
941 }
942
943 static int
cam_iosched_sbintime_sysctl(SYSCTL_HANDLER_ARGS)944 cam_iosched_sbintime_sysctl(SYSCTL_HANDLER_ARGS)
945 {
946 char buf[16];
947 sbintime_t value;
948 int error;
949 uint64_t us;
950
951 value = *(sbintime_t *)arg1;
952 us = (uint64_t)value / SBT_1US;
953 snprintf(buf, sizeof(buf), "%ju", (intmax_t)us);
954 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
955 if (error != 0 || req->newptr == NULL)
956 return error;
957 us = strtoul(buf, NULL, 10);
958 if (us == 0)
959 return EINVAL;
960 *(sbintime_t *)arg1 = us * SBT_1US;
961 return 0;
962 }
963
964 static int
cam_iosched_sysctl_latencies(SYSCTL_HANDLER_ARGS)965 cam_iosched_sysctl_latencies(SYSCTL_HANDLER_ARGS)
966 {
967 int i, error;
968 struct sbuf sb;
969 uint64_t *latencies;
970
971 latencies = arg1;
972 sbuf_new_for_sysctl(&sb, NULL, LAT_BUCKETS * 16, req);
973
974 for (i = 0; i < LAT_BUCKETS - 1; i++)
975 sbuf_printf(&sb, "%jd,", (intmax_t)latencies[i]);
976 sbuf_printf(&sb, "%jd", (intmax_t)latencies[LAT_BUCKETS - 1]);
977 error = sbuf_finish(&sb);
978 sbuf_delete(&sb);
979
980 return (error);
981 }
982
983 static int
cam_iosched_quanta_sysctl(SYSCTL_HANDLER_ARGS)984 cam_iosched_quanta_sysctl(SYSCTL_HANDLER_ARGS)
985 {
986 int *quanta;
987 int error, value;
988
989 quanta = (unsigned *)arg1;
990 value = *quanta;
991
992 error = sysctl_handle_int(oidp, (int *)&value, 0, req);
993 if ((error != 0) || (req->newptr == NULL))
994 return (error);
995
996 if (value < 1 || value > hz)
997 return (EINVAL);
998
999 *quanta = value;
1000
1001 return (0);
1002 }
1003
1004 static void
cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc * isc,struct iop_stats * ios,char * name)1005 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct iop_stats *ios, char *name)
1006 {
1007 struct sysctl_oid_list *n;
1008 struct sysctl_ctx_list *ctx;
1009
1010 ios->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx,
1011 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, name,
1012 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, name);
1013 n = SYSCTL_CHILDREN(ios->sysctl_tree);
1014 ctx = &ios->sysctl_ctx;
1015
1016 SYSCTL_ADD_UQUAD(ctx, n,
1017 OID_AUTO, "ema", CTLFLAG_RD,
1018 &ios->ema,
1019 "Fast Exponentially Weighted Moving Average");
1020 SYSCTL_ADD_UQUAD(ctx, n,
1021 OID_AUTO, "emvar", CTLFLAG_RD,
1022 &ios->emvar,
1023 "Fast Exponentially Weighted Moving Variance");
1024
1025 SYSCTL_ADD_INT(ctx, n,
1026 OID_AUTO, "pending", CTLFLAG_RD,
1027 &ios->pending, 0,
1028 "Instantaneous # of pending transactions");
1029 SYSCTL_ADD_INT(ctx, n,
1030 OID_AUTO, "count", CTLFLAG_RD,
1031 &ios->total, 0,
1032 "# of transactions submitted to hardware");
1033 SYSCTL_ADD_INT(ctx, n,
1034 OID_AUTO, "queued", CTLFLAG_RD,
1035 &ios->queued, 0,
1036 "# of transactions in the queue");
1037 SYSCTL_ADD_INT(ctx, n,
1038 OID_AUTO, "in", CTLFLAG_RD,
1039 &ios->in, 0,
1040 "# of transactions queued to driver");
1041 SYSCTL_ADD_INT(ctx, n,
1042 OID_AUTO, "out", CTLFLAG_RD,
1043 &ios->out, 0,
1044 "# of transactions completed (including with error)");
1045 SYSCTL_ADD_INT(ctx, n,
1046 OID_AUTO, "errs", CTLFLAG_RD,
1047 &ios->errs, 0,
1048 "# of transactions completed with an error");
1049
1050 SYSCTL_ADD_PROC(ctx, n,
1051 OID_AUTO, "limiter",
1052 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE,
1053 ios, 0, cam_iosched_limiter_sysctl, "A",
1054 "Current limiting type.");
1055 SYSCTL_ADD_INT(ctx, n,
1056 OID_AUTO, "min", CTLFLAG_RW,
1057 &ios->min, 0,
1058 "min resource");
1059 SYSCTL_ADD_INT(ctx, n,
1060 OID_AUTO, "max", CTLFLAG_RW,
1061 &ios->max, 0,
1062 "max resource");
1063 SYSCTL_ADD_INT(ctx, n,
1064 OID_AUTO, "current", CTLFLAG_RW,
1065 &ios->current, 0,
1066 "current resource");
1067
1068 SYSCTL_ADD_PROC(ctx, n,
1069 OID_AUTO, "latencies",
1070 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
1071 &ios->latencies, 0,
1072 cam_iosched_sysctl_latencies, "A",
1073 "Array of latencies, a geometric progresson from\n"
1074 "kern.cam.iosched.bucket_base_us with a ratio of\n"
1075 "kern.cam.iosched.bucket_ration / 100 from one to\n"
1076 "the next. By default 20 steps from 20us to 10.485s\n"
1077 "by doubling.");
1078
1079 }
1080
1081 static void
cam_iosched_iop_stats_fini(struct iop_stats * ios)1082 cam_iosched_iop_stats_fini(struct iop_stats *ios)
1083 {
1084 if (ios->sysctl_tree)
1085 if (sysctl_ctx_free(&ios->sysctl_ctx) != 0)
1086 printf("can't remove iosched sysctl stats context\n");
1087 }
1088
1089 static void
cam_iosched_cl_sysctl_init(struct cam_iosched_softc * isc)1090 cam_iosched_cl_sysctl_init(struct cam_iosched_softc *isc)
1091 {
1092 struct sysctl_oid_list *n;
1093 struct sysctl_ctx_list *ctx;
1094 struct control_loop *clp;
1095
1096 clp = &isc->cl;
1097 clp->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx,
1098 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, "control",
1099 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "Control loop info");
1100 n = SYSCTL_CHILDREN(clp->sysctl_tree);
1101 ctx = &clp->sysctl_ctx;
1102
1103 SYSCTL_ADD_PROC(ctx, n,
1104 OID_AUTO, "type",
1105 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE,
1106 clp, 0, cam_iosched_control_type_sysctl, "A",
1107 "Control loop algorithm");
1108 SYSCTL_ADD_PROC(ctx, n,
1109 OID_AUTO, "steer_interval",
1110 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE,
1111 &clp->steer_interval, 0, cam_iosched_sbintime_sysctl, "A",
1112 "How often to steer (in us)");
1113 SYSCTL_ADD_PROC(ctx, n,
1114 OID_AUTO, "lolat",
1115 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE,
1116 &clp->lolat, 0, cam_iosched_sbintime_sysctl, "A",
1117 "Low water mark for Latency (in us)");
1118 SYSCTL_ADD_PROC(ctx, n,
1119 OID_AUTO, "hilat",
1120 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE,
1121 &clp->hilat, 0, cam_iosched_sbintime_sysctl, "A",
1122 "Hi water mark for Latency (in us)");
1123 SYSCTL_ADD_INT(ctx, n,
1124 OID_AUTO, "alpha", CTLFLAG_RW,
1125 &clp->alpha, 0,
1126 "Alpha for PLL (x100) aka gain");
1127 }
1128
1129 static void
cam_iosched_cl_sysctl_fini(struct control_loop * clp)1130 cam_iosched_cl_sysctl_fini(struct control_loop *clp)
1131 {
1132 if (clp->sysctl_tree)
1133 if (sysctl_ctx_free(&clp->sysctl_ctx) != 0)
1134 printf("can't remove iosched sysctl control loop context\n");
1135 }
1136 #endif
1137
1138 /*
1139 * Allocate the iosched structure. This also insulates callers from knowing
1140 * sizeof struct cam_iosched_softc.
1141 */
1142 int
cam_iosched_init(struct cam_iosched_softc ** iscp,struct cam_periph * periph)1143 cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph)
1144 {
1145
1146 *iscp = malloc(sizeof(**iscp), M_CAMSCHED, M_NOWAIT | M_ZERO);
1147 if (*iscp == NULL)
1148 return ENOMEM;
1149 #ifdef CAM_IOSCHED_DYNAMIC
1150 if (iosched_debug)
1151 printf("CAM IOSCHEDULER Allocating entry at %p\n", *iscp);
1152 #endif
1153 (*iscp)->sort_io_queue = -1;
1154 bioq_init(&(*iscp)->bio_queue);
1155 bioq_init(&(*iscp)->trim_queue);
1156 #ifdef CAM_IOSCHED_DYNAMIC
1157 if (do_dynamic_iosched) {
1158 bioq_init(&(*iscp)->write_queue);
1159 (*iscp)->read_bias = default_read_bias;
1160 (*iscp)->current_read_bias = 0;
1161 (*iscp)->quanta = min(hz, 200);
1162 cam_iosched_iop_stats_init(*iscp, &(*iscp)->read_stats);
1163 cam_iosched_iop_stats_init(*iscp, &(*iscp)->write_stats);
1164 cam_iosched_iop_stats_init(*iscp, &(*iscp)->trim_stats);
1165 (*iscp)->trim_stats.max = 1; /* Trims are special: one at a time for now */
1166 (*iscp)->last_time = sbinuptime();
1167 callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0);
1168 (*iscp)->periph = periph;
1169 cam_iosched_cl_init(&(*iscp)->cl, *iscp);
1170 callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta, cam_iosched_ticker, *iscp);
1171 (*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
1172 }
1173 #endif
1174
1175 return 0;
1176 }
1177
1178 /*
1179 * Reclaim all used resources. This assumes that other folks have
1180 * drained the requests in the hardware. Maybe an unwise assumption.
1181 */
1182 void
cam_iosched_fini(struct cam_iosched_softc * isc)1183 cam_iosched_fini(struct cam_iosched_softc *isc)
1184 {
1185 if (isc) {
1186 cam_iosched_flush(isc, NULL, ENXIO);
1187 #ifdef CAM_IOSCHED_DYNAMIC
1188 cam_iosched_iop_stats_fini(&isc->read_stats);
1189 cam_iosched_iop_stats_fini(&isc->write_stats);
1190 cam_iosched_iop_stats_fini(&isc->trim_stats);
1191 cam_iosched_cl_sysctl_fini(&isc->cl);
1192 if (isc->sysctl_tree)
1193 if (sysctl_ctx_free(&isc->sysctl_ctx) != 0)
1194 printf("can't remove iosched sysctl stats context\n");
1195 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) {
1196 callout_drain(&isc->ticker);
1197 isc->flags &= ~ CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
1198 }
1199 #endif
1200 free(isc, M_CAMSCHED);
1201 }
1202 }
1203
1204 /*
1205 * After we're sure we're attaching a device, go ahead and add
1206 * hooks for any sysctl we may wish to honor.
1207 */
cam_iosched_sysctl_init(struct cam_iosched_softc * isc,struct sysctl_ctx_list * ctx,struct sysctl_oid * node)1208 void cam_iosched_sysctl_init(struct cam_iosched_softc *isc,
1209 struct sysctl_ctx_list *ctx, struct sysctl_oid *node)
1210 {
1211 struct sysctl_oid_list *n;
1212
1213 n = SYSCTL_CHILDREN(node);
1214 SYSCTL_ADD_INT(ctx, n,
1215 OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE,
1216 &isc->sort_io_queue, 0,
1217 "Sort IO queue to try and optimise disk access patterns");
1218 SYSCTL_ADD_INT(ctx, n,
1219 OID_AUTO, "trim_goal", CTLFLAG_RW,
1220 &isc->trim_goal, 0,
1221 "Number of trims to try to accumulate before sending to hardware");
1222 SYSCTL_ADD_INT(ctx, n,
1223 OID_AUTO, "trim_ticks", CTLFLAG_RW,
1224 &isc->trim_goal, 0,
1225 "IO Schedul qaunta to hold back trims for when accumulating");
1226
1227 #ifdef CAM_IOSCHED_DYNAMIC
1228 if (!do_dynamic_iosched)
1229 return;
1230
1231 isc->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx,
1232 SYSCTL_CHILDREN(node), OID_AUTO, "iosched",
1233 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "I/O scheduler statistics");
1234 n = SYSCTL_CHILDREN(isc->sysctl_tree);
1235 ctx = &isc->sysctl_ctx;
1236
1237 cam_iosched_iop_stats_sysctl_init(isc, &isc->read_stats, "read");
1238 cam_iosched_iop_stats_sysctl_init(isc, &isc->write_stats, "write");
1239 cam_iosched_iop_stats_sysctl_init(isc, &isc->trim_stats, "trim");
1240 cam_iosched_cl_sysctl_init(isc);
1241
1242 SYSCTL_ADD_INT(ctx, n,
1243 OID_AUTO, "read_bias", CTLFLAG_RW,
1244 &isc->read_bias, default_read_bias,
1245 "How biased towards read should we be independent of limits");
1246
1247 SYSCTL_ADD_PROC(ctx, n,
1248 OID_AUTO, "quanta", CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE,
1249 &isc->quanta, 0, cam_iosched_quanta_sysctl, "I",
1250 "How many quanta per second do we slice the I/O up into");
1251
1252 SYSCTL_ADD_INT(ctx, n,
1253 OID_AUTO, "total_ticks", CTLFLAG_RD,
1254 &isc->total_ticks, 0,
1255 "Total number of ticks we've done");
1256
1257 SYSCTL_ADD_INT(ctx, n,
1258 OID_AUTO, "load", CTLFLAG_RD,
1259 &isc->load, 0,
1260 "scaled load average / 100");
1261
1262 SYSCTL_ADD_U64(ctx, n,
1263 OID_AUTO, "latency_trigger", CTLFLAG_RW,
1264 &isc->max_lat, 0,
1265 "Latency treshold to trigger callbacks");
1266 #endif
1267 }
1268
1269 void
cam_iosched_set_latfcn(struct cam_iosched_softc * isc,cam_iosched_latfcn_t fnp,void * argp)1270 cam_iosched_set_latfcn(struct cam_iosched_softc *isc,
1271 cam_iosched_latfcn_t fnp, void *argp)
1272 {
1273 #ifdef CAM_IOSCHED_DYNAMIC
1274 isc->latfcn = fnp;
1275 isc->latarg = argp;
1276 #endif
1277 }
1278
1279 /*
1280 * Client drivers can set two parameters. "goal" is the number of BIO_DELETEs
1281 * that will be queued up before iosched will "release" the trims to the client
1282 * driver to wo with what they will (usually combine as many as possible). If we
1283 * don't get this many, after trim_ticks we'll submit the I/O anyway with
1284 * whatever we have. We do need an I/O of some kind of to clock the deferred
1285 * trims out to disk. Since we will eventually get a write for the super block
1286 * or something before we shutdown, the trims will complete. To be safe, when a
1287 * BIO_FLUSH is presented to the iosched work queue, we set the ticks time far
1288 * enough in the past so we'll present the BIO_DELETEs to the client driver.
1289 * There might be a race if no BIO_DELETESs were queued, a BIO_FLUSH comes in
1290 * and then a BIO_DELETE is sent down. No know client does this, and there's
1291 * already a race between an ordered BIO_FLUSH and any BIO_DELETEs in flight,
1292 * but no client depends on the ordering being honored.
1293 *
1294 * XXX I'm not sure what the interaction between UFS direct BIOs and the BUF
1295 * flushing on shutdown. I think there's bufs that would be dependent on the BIO
1296 * finishing to write out at least metadata, so we'll be fine. To be safe, keep
1297 * the number of ticks low (less than maybe 10s) to avoid shutdown races.
1298 */
1299
1300 void
cam_iosched_set_trim_goal(struct cam_iosched_softc * isc,int goal)1301 cam_iosched_set_trim_goal(struct cam_iosched_softc *isc, int goal)
1302 {
1303
1304 isc->trim_goal = goal;
1305 }
1306
1307 void
cam_iosched_set_trim_ticks(struct cam_iosched_softc * isc,int trim_ticks)1308 cam_iosched_set_trim_ticks(struct cam_iosched_softc *isc, int trim_ticks)
1309 {
1310
1311 isc->trim_ticks = trim_ticks;
1312 }
1313
1314 /*
1315 * Flush outstanding I/O. Consumers of this library don't know all the
1316 * queues we may keep, so this allows all I/O to be flushed in one
1317 * convenient call.
1318 */
1319 void
cam_iosched_flush(struct cam_iosched_softc * isc,struct devstat * stp,int err)1320 cam_iosched_flush(struct cam_iosched_softc *isc, struct devstat *stp, int err)
1321 {
1322 bioq_flush(&isc->bio_queue, stp, err);
1323 bioq_flush(&isc->trim_queue, stp, err);
1324 #ifdef CAM_IOSCHED_DYNAMIC
1325 if (do_dynamic_iosched)
1326 bioq_flush(&isc->write_queue, stp, err);
1327 #endif
1328 }
1329
1330 #ifdef CAM_IOSCHED_DYNAMIC
1331 static struct bio *
cam_iosched_get_write(struct cam_iosched_softc * isc)1332 cam_iosched_get_write(struct cam_iosched_softc *isc)
1333 {
1334 struct bio *bp;
1335
1336 /*
1337 * We control the write rate by controlling how many requests we send
1338 * down to the drive at any one time. Fewer requests limits the
1339 * effects of both starvation when the requests take a while and write
1340 * amplification when each request is causing more than one write to
1341 * the NAND media. Limiting the queue depth like this will also limit
1342 * the write throughput and give and reads that want to compete to
1343 * compete unfairly.
1344 */
1345 bp = bioq_first(&isc->write_queue);
1346 if (bp == NULL) {
1347 if (iosched_debug > 3)
1348 printf("No writes present in write_queue\n");
1349 return NULL;
1350 }
1351
1352 /*
1353 * If pending read, prefer that based on current read bias
1354 * setting.
1355 */
1356 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) {
1357 if (iosched_debug)
1358 printf(
1359 "Reads present and current_read_bias is %d queued "
1360 "writes %d queued reads %d\n",
1361 isc->current_read_bias, isc->write_stats.queued,
1362 isc->read_stats.queued);
1363 isc->current_read_bias--;
1364 /* We're not limiting writes, per se, just doing reads first */
1365 return NULL;
1366 }
1367
1368 /*
1369 * See if our current limiter allows this I/O.
1370 */
1371 if (cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) {
1372 if (iosched_debug)
1373 printf("Can't write because limiter says no.\n");
1374 isc->write_stats.state_flags |= IOP_RATE_LIMITED;
1375 return NULL;
1376 }
1377
1378 /*
1379 * Let's do this: We've passed all the gates and we're a go
1380 * to schedule the I/O in the SIM.
1381 */
1382 isc->current_read_bias = isc->read_bias;
1383 bioq_remove(&isc->write_queue, bp);
1384 if (bp->bio_cmd == BIO_WRITE) {
1385 isc->write_stats.queued--;
1386 isc->write_stats.total++;
1387 isc->write_stats.pending++;
1388 }
1389 if (iosched_debug > 9)
1390 printf("HWQ : %p %#x\n", bp, bp->bio_cmd);
1391 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED;
1392 return bp;
1393 }
1394 #endif
1395
1396 /*
1397 * Put back a trim that you weren't able to actually schedule this time.
1398 */
1399 void
cam_iosched_put_back_trim(struct cam_iosched_softc * isc,struct bio * bp)1400 cam_iosched_put_back_trim(struct cam_iosched_softc *isc, struct bio *bp)
1401 {
1402 bioq_insert_head(&isc->trim_queue, bp);
1403 if (isc->queued_trims == 0)
1404 isc->last_trim_tick = ticks;
1405 isc->queued_trims++;
1406 #ifdef CAM_IOSCHED_DYNAMIC
1407 isc->trim_stats.queued++;
1408 isc->trim_stats.total--; /* since we put it back, don't double count */
1409 isc->trim_stats.pending--;
1410 #endif
1411 }
1412
1413 /*
1414 * gets the next trim from the trim queue.
1415 *
1416 * Assumes we're called with the periph lock held. It removes this
1417 * trim from the queue and the device must explicitly reinsert it
1418 * should the need arise.
1419 */
1420 struct bio *
cam_iosched_next_trim(struct cam_iosched_softc * isc)1421 cam_iosched_next_trim(struct cam_iosched_softc *isc)
1422 {
1423 struct bio *bp;
1424
1425 bp = bioq_first(&isc->trim_queue);
1426 if (bp == NULL)
1427 return NULL;
1428 bioq_remove(&isc->trim_queue, bp);
1429 isc->queued_trims--;
1430 isc->last_trim_tick = ticks; /* Reset the tick timer when we take trims */
1431 #ifdef CAM_IOSCHED_DYNAMIC
1432 isc->trim_stats.queued--;
1433 isc->trim_stats.total++;
1434 isc->trim_stats.pending++;
1435 #endif
1436 return bp;
1437 }
1438
1439 /*
1440 * gets an available trim from the trim queue, if there's no trim
1441 * already pending. It removes this trim from the queue and the device
1442 * must explicitly reinsert it should the need arise.
1443 *
1444 * Assumes we're called with the periph lock held.
1445 */
1446 struct bio *
cam_iosched_get_trim(struct cam_iosched_softc * isc)1447 cam_iosched_get_trim(struct cam_iosched_softc *isc)
1448 {
1449 #ifdef CAM_IOSCHED_DYNAMIC
1450 struct bio *bp;
1451 #endif
1452
1453 if (!cam_iosched_has_more_trim(isc))
1454 return NULL;
1455 #ifdef CAM_IOSCHED_DYNAMIC
1456 bp = bioq_first(&isc->trim_queue);
1457 if (bp == NULL)
1458 return NULL;
1459
1460 /*
1461 * If pending read, prefer that based on current read bias setting. The
1462 * read bias is shared for both writes and TRIMs, but on TRIMs the bias
1463 * is for a combined TRIM not a single TRIM request that's come in.
1464 */
1465 if (do_dynamic_iosched) {
1466 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) {
1467 if (iosched_debug)
1468 printf("Reads present and current_read_bias is %d"
1469 " queued trims %d queued reads %d\n",
1470 isc->current_read_bias, isc->trim_stats.queued,
1471 isc->read_stats.queued);
1472 isc->current_read_bias--;
1473 /* We're not limiting TRIMS, per se, just doing reads first */
1474 return NULL;
1475 }
1476 /*
1477 * We're going to do a trim, so reset the bias.
1478 */
1479 isc->current_read_bias = isc->read_bias;
1480 }
1481
1482 /*
1483 * See if our current limiter allows this I/O. Because we only call this
1484 * here, and not in next_trim, the 'bandwidth' limits for trims won't
1485 * work, while the iops or max queued limits will work. It's tricky
1486 * because we want the limits to be from the perspective of the
1487 * "commands sent to the device." To make iops work, we need to check
1488 * only here (since we want all the ops we combine to count as one). To
1489 * make bw limits work, we'd need to check in next_trim, but that would
1490 * have the effect of limiting the iops as seen from the upper layers.
1491 */
1492 if (cam_iosched_limiter_iop(&isc->trim_stats, bp) != 0) {
1493 if (iosched_debug)
1494 printf("Can't trim because limiter says no.\n");
1495 isc->trim_stats.state_flags |= IOP_RATE_LIMITED;
1496 return NULL;
1497 }
1498 isc->current_read_bias = isc->read_bias;
1499 isc->trim_stats.state_flags &= ~IOP_RATE_LIMITED;
1500 /* cam_iosched_next_trim below keeps proper book */
1501 #endif
1502 return cam_iosched_next_trim(isc);
1503 }
1504
1505
1506 #ifdef CAM_IOSCHED_DYNAMIC
1507 static struct bio *
bio_next(struct bio * bp)1508 bio_next(struct bio *bp)
1509 {
1510 bp = TAILQ_NEXT(bp, bio_queue);
1511 /*
1512 * After the first commands, the ordered bit terminates
1513 * our search because BIO_ORDERED acts like a barrier.
1514 */
1515 if (bp == NULL || bp->bio_flags & BIO_ORDERED)
1516 return NULL;
1517 return bp;
1518 }
1519
1520 static bool
cam_iosched_rate_limited(struct iop_stats * ios)1521 cam_iosched_rate_limited(struct iop_stats *ios)
1522 {
1523 return ios->state_flags & IOP_RATE_LIMITED;
1524 }
1525 #endif
1526
1527 /*
1528 * Determine what the next bit of work to do is for the periph. The
1529 * default implementation looks to see if we have trims to do, but no
1530 * trims outstanding. If so, we do that. Otherwise we see if we have
1531 * other work. If we do, then we do that. Otherwise why were we called?
1532 */
1533 struct bio *
cam_iosched_next_bio(struct cam_iosched_softc * isc)1534 cam_iosched_next_bio(struct cam_iosched_softc *isc)
1535 {
1536 struct bio *bp;
1537
1538 /*
1539 * See if we have a trim that can be scheduled. We can only send one
1540 * at a time down, so this takes that into account.
1541 *
1542 * XXX newer TRIM commands are queueable. Revisit this when we
1543 * implement them.
1544 */
1545 if ((bp = cam_iosched_get_trim(isc)) != NULL)
1546 return bp;
1547
1548 #ifdef CAM_IOSCHED_DYNAMIC
1549 /*
1550 * See if we have any pending writes, room in the queue for them,
1551 * and no pending reads (unless we've scheduled too many).
1552 * if so, those are next.
1553 */
1554 if (do_dynamic_iosched) {
1555 if ((bp = cam_iosched_get_write(isc)) != NULL)
1556 return bp;
1557 }
1558 #endif
1559 /*
1560 * next, see if there's other, normal I/O waiting. If so return that.
1561 */
1562 #ifdef CAM_IOSCHED_DYNAMIC
1563 if (do_dynamic_iosched) {
1564 for (bp = bioq_first(&isc->bio_queue); bp != NULL;
1565 bp = bio_next(bp)) {
1566 /*
1567 * For the dynamic scheduler with a read bias, bio_queue
1568 * is only for reads. However, without one, all
1569 * operations are queued. Enforce limits here for any
1570 * operation we find here.
1571 */
1572 if (bp->bio_cmd == BIO_READ) {
1573 if (cam_iosched_rate_limited(&isc->read_stats) ||
1574 cam_iosched_limiter_iop(&isc->read_stats, bp) != 0) {
1575 isc->read_stats.state_flags |= IOP_RATE_LIMITED;
1576 continue;
1577 }
1578 isc->read_stats.state_flags &= ~IOP_RATE_LIMITED;
1579 }
1580 /*
1581 * There can only be write requests on the queue when
1582 * the read bias is 0, but we need to process them
1583 * here. We do not assert for read bias == 0, however,
1584 * since it is dynamic and we can have WRITE operations
1585 * in the queue after we transition from 0 to non-zero.
1586 */
1587 if (bp->bio_cmd == BIO_WRITE) {
1588 if (cam_iosched_rate_limited(&isc->write_stats) ||
1589 cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) {
1590 isc->write_stats.state_flags |= IOP_RATE_LIMITED;
1591 continue;
1592 }
1593 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED;
1594 }
1595 /*
1596 * here we know we have a bp that's != NULL, that's not rate limited
1597 * and can be the next I/O.
1598 */
1599 break;
1600 }
1601 } else
1602 #endif
1603 bp = bioq_first(&isc->bio_queue);
1604
1605 if (bp == NULL)
1606 return (NULL);
1607 bioq_remove(&isc->bio_queue, bp);
1608 #ifdef CAM_IOSCHED_DYNAMIC
1609 if (do_dynamic_iosched) {
1610 if (bp->bio_cmd == BIO_READ) {
1611 isc->read_stats.queued--;
1612 isc->read_stats.total++;
1613 isc->read_stats.pending++;
1614 } else if (bp->bio_cmd == BIO_WRITE) {
1615 isc->write_stats.queued--;
1616 isc->write_stats.total++;
1617 isc->write_stats.pending++;
1618 }
1619 }
1620 if (iosched_debug > 9)
1621 printf("HWQ : %p %#x\n", bp, bp->bio_cmd);
1622 #endif
1623 return bp;
1624 }
1625
1626 /*
1627 * Driver has been given some work to do by the block layer. Tell the
1628 * scheduler about it and have it queue the work up. The scheduler module
1629 * will then return the currently most useful bit of work later, possibly
1630 * deferring work for various reasons.
1631 */
1632 void
cam_iosched_queue_work(struct cam_iosched_softc * isc,struct bio * bp)1633 cam_iosched_queue_work(struct cam_iosched_softc *isc, struct bio *bp)
1634 {
1635
1636 /*
1637 * A BIO_SPEEDUP from the upper layers means that they have a block
1638 * shortage. At the present, this is only sent when we're trying to
1639 * allocate blocks, but have a shortage before giving up. bio_length is
1640 * the size of their shortage. We will complete just enough BIO_DELETEs
1641 * in the queue to satisfy the need. If bio_length is 0, we'll complete
1642 * them all. This allows the scheduler to delay BIO_DELETEs to improve
1643 * read/write performance without worrying about the upper layers. When
1644 * it's possibly a problem, we respond by pretending the BIO_DELETEs
1645 * just worked. We can't do anything about the BIO_DELETEs in the
1646 * hardware, though. We have to wait for them to complete.
1647 */
1648 if (bp->bio_cmd == BIO_SPEEDUP) {
1649 off_t len;
1650 struct bio *nbp;
1651
1652 len = 0;
1653 while (bioq_first(&isc->trim_queue) &&
1654 (bp->bio_length == 0 || len < bp->bio_length)) {
1655 nbp = bioq_takefirst(&isc->trim_queue);
1656 len += nbp->bio_length;
1657 nbp->bio_error = 0;
1658 biodone(nbp);
1659 }
1660 if (bp->bio_length > 0) {
1661 if (bp->bio_length > len)
1662 bp->bio_resid = bp->bio_length - len;
1663 else
1664 bp->bio_resid = 0;
1665 }
1666 bp->bio_error = 0;
1667 biodone(bp);
1668 return;
1669 }
1670
1671 /*
1672 * If we get a BIO_FLUSH, and we're doing delayed BIO_DELETEs then we
1673 * set the last tick time to one less than the current ticks minus the
1674 * delay to force the BIO_DELETEs to be presented to the client driver.
1675 */
1676 if (bp->bio_cmd == BIO_FLUSH && isc->trim_ticks > 0)
1677 isc->last_trim_tick = ticks - isc->trim_ticks - 1;
1678
1679 /*
1680 * Put all trims on the trim queue. Otherwise put the work on the bio
1681 * queue.
1682 */
1683 if (bp->bio_cmd == BIO_DELETE) {
1684 bioq_insert_tail(&isc->trim_queue, bp);
1685 if (isc->queued_trims == 0)
1686 isc->last_trim_tick = ticks;
1687 isc->queued_trims++;
1688 #ifdef CAM_IOSCHED_DYNAMIC
1689 isc->trim_stats.in++;
1690 isc->trim_stats.queued++;
1691 #endif
1692 }
1693 #ifdef CAM_IOSCHED_DYNAMIC
1694 else if (do_dynamic_iosched && isc->read_bias != 0 &&
1695 (bp->bio_cmd != BIO_READ)) {
1696 if (cam_iosched_sort_queue(isc))
1697 bioq_disksort(&isc->write_queue, bp);
1698 else
1699 bioq_insert_tail(&isc->write_queue, bp);
1700 if (iosched_debug > 9)
1701 printf("Qw : %p %#x\n", bp, bp->bio_cmd);
1702 if (bp->bio_cmd == BIO_WRITE) {
1703 isc->write_stats.in++;
1704 isc->write_stats.queued++;
1705 }
1706 }
1707 #endif
1708 else {
1709 if (cam_iosched_sort_queue(isc))
1710 bioq_disksort(&isc->bio_queue, bp);
1711 else
1712 bioq_insert_tail(&isc->bio_queue, bp);
1713 #ifdef CAM_IOSCHED_DYNAMIC
1714 if (iosched_debug > 9)
1715 printf("Qr : %p %#x\n", bp, bp->bio_cmd);
1716 if (bp->bio_cmd == BIO_READ) {
1717 isc->read_stats.in++;
1718 isc->read_stats.queued++;
1719 } else if (bp->bio_cmd == BIO_WRITE) {
1720 isc->write_stats.in++;
1721 isc->write_stats.queued++;
1722 }
1723 #endif
1724 }
1725 }
1726
1727 /*
1728 * If we have work, get it scheduled. Called with the periph lock held.
1729 */
1730 void
cam_iosched_schedule(struct cam_iosched_softc * isc,struct cam_periph * periph)1731 cam_iosched_schedule(struct cam_iosched_softc *isc, struct cam_periph *periph)
1732 {
1733
1734 if (cam_iosched_has_work(isc))
1735 xpt_schedule(periph, CAM_PRIORITY_NORMAL);
1736 }
1737
1738 /*
1739 * Complete a trim request. Mark that we no longer have one in flight.
1740 */
1741 void
cam_iosched_trim_done(struct cam_iosched_softc * isc)1742 cam_iosched_trim_done(struct cam_iosched_softc *isc)
1743 {
1744
1745 isc->flags &= ~CAM_IOSCHED_FLAG_TRIM_ACTIVE;
1746 }
1747
1748 /*
1749 * Complete a bio. Called before we release the ccb with xpt_release_ccb so we
1750 * might use notes in the ccb for statistics.
1751 */
1752 int
cam_iosched_bio_complete(struct cam_iosched_softc * isc,struct bio * bp,union ccb * done_ccb)1753 cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp,
1754 union ccb *done_ccb)
1755 {
1756 int retval = 0;
1757 #ifdef CAM_IOSCHED_DYNAMIC
1758 if (!do_dynamic_iosched)
1759 return retval;
1760
1761 if (iosched_debug > 10)
1762 printf("done: %p %#x\n", bp, bp->bio_cmd);
1763 if (bp->bio_cmd == BIO_WRITE) {
1764 retval = cam_iosched_limiter_iodone(&isc->write_stats, bp);
1765 if ((bp->bio_flags & BIO_ERROR) != 0)
1766 isc->write_stats.errs++;
1767 isc->write_stats.out++;
1768 isc->write_stats.pending--;
1769 } else if (bp->bio_cmd == BIO_READ) {
1770 retval = cam_iosched_limiter_iodone(&isc->read_stats, bp);
1771 if ((bp->bio_flags & BIO_ERROR) != 0)
1772 isc->read_stats.errs++;
1773 isc->read_stats.out++;
1774 isc->read_stats.pending--;
1775 } else if (bp->bio_cmd == BIO_DELETE) {
1776 if ((bp->bio_flags & BIO_ERROR) != 0)
1777 isc->trim_stats.errs++;
1778 isc->trim_stats.out++;
1779 isc->trim_stats.pending--;
1780 } else if (bp->bio_cmd != BIO_FLUSH) {
1781 if (iosched_debug)
1782 printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd);
1783 }
1784
1785 if ((bp->bio_flags & BIO_ERROR) == 0 && done_ccb != NULL &&
1786 (done_ccb->ccb_h.status & CAM_QOS_VALID) != 0) {
1787 sbintime_t sim_latency;
1788
1789 sim_latency = cam_iosched_sbintime_t(done_ccb->ccb_h.qos.periph_data);
1790
1791 cam_iosched_io_metric_update(isc, sim_latency,
1792 bp->bio_cmd, bp->bio_bcount);
1793 /*
1794 * Debugging code: allow callbacks to the periph driver when latency max
1795 * is exceeded. This can be useful for triggering external debugging actions.
1796 */
1797 if (isc->latfcn && isc->max_lat != 0 && sim_latency > isc->max_lat)
1798 isc->latfcn(isc->latarg, sim_latency, bp);
1799 }
1800
1801 #endif
1802 return retval;
1803 }
1804
1805 /*
1806 * Tell the io scheduler that you've pushed a trim down into the sim.
1807 * This also tells the I/O scheduler not to push any more trims down, so
1808 * some periphs do not call it if they can cope with multiple trims in flight.
1809 */
1810 void
cam_iosched_submit_trim(struct cam_iosched_softc * isc)1811 cam_iosched_submit_trim(struct cam_iosched_softc *isc)
1812 {
1813
1814 isc->flags |= CAM_IOSCHED_FLAG_TRIM_ACTIVE;
1815 }
1816
1817 /*
1818 * Change the sorting policy hint for I/O transactions for this device.
1819 */
1820 void
cam_iosched_set_sort_queue(struct cam_iosched_softc * isc,int val)1821 cam_iosched_set_sort_queue(struct cam_iosched_softc *isc, int val)
1822 {
1823
1824 isc->sort_io_queue = val;
1825 }
1826
1827 int
cam_iosched_has_work_flags(struct cam_iosched_softc * isc,uint32_t flags)1828 cam_iosched_has_work_flags(struct cam_iosched_softc *isc, uint32_t flags)
1829 {
1830 return isc->flags & flags;
1831 }
1832
1833 void
cam_iosched_set_work_flags(struct cam_iosched_softc * isc,uint32_t flags)1834 cam_iosched_set_work_flags(struct cam_iosched_softc *isc, uint32_t flags)
1835 {
1836 isc->flags |= flags;
1837 }
1838
1839 void
cam_iosched_clr_work_flags(struct cam_iosched_softc * isc,uint32_t flags)1840 cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags)
1841 {
1842 isc->flags &= ~flags;
1843 }
1844
1845 #ifdef CAM_IOSCHED_DYNAMIC
1846 /*
1847 * After the method presented in Jack Crenshaw's 1998 article "Integer
1848 * Square Roots," reprinted at
1849 * http://www.embedded.com/electronics-blogs/programmer-s-toolbox/4219659/Integer-Square-Roots
1850 * and well worth the read. Briefly, we find the power of 4 that's the
1851 * largest smaller than val. We then check each smaller power of 4 to
1852 * see if val is still bigger. The right shifts at each step divide
1853 * the result by 2 which after successive application winds up
1854 * accumulating the right answer. It could also have been accumulated
1855 * using a separate root counter, but this code is smaller and faster
1856 * than that method. This method is also integer size invariant.
1857 * It returns floor(sqrt((float)val)), or the largest integer less than
1858 * or equal to the square root.
1859 */
1860 static uint64_t
isqrt64(uint64_t val)1861 isqrt64(uint64_t val)
1862 {
1863 uint64_t res = 0;
1864 uint64_t bit = 1ULL << (sizeof(uint64_t) * NBBY - 2);
1865
1866 /*
1867 * Find the largest power of 4 smaller than val.
1868 */
1869 while (bit > val)
1870 bit >>= 2;
1871
1872 /*
1873 * Accumulate the answer, one bit at a time (we keep moving
1874 * them over since 2 is the square root of 4 and we test
1875 * powers of 4). We accumulate where we find the bit, but
1876 * the successive shifts land the bit in the right place
1877 * by the end.
1878 */
1879 while (bit != 0) {
1880 if (val >= res + bit) {
1881 val -= res + bit;
1882 res = (res >> 1) + bit;
1883 } else
1884 res >>= 1;
1885 bit >>= 2;
1886 }
1887
1888 return res;
1889 }
1890
1891 static sbintime_t latencies[LAT_BUCKETS - 1] = {
1892 BUCKET_BASE << 0, /* 20us */
1893 BUCKET_BASE << 1,
1894 BUCKET_BASE << 2,
1895 BUCKET_BASE << 3,
1896 BUCKET_BASE << 4,
1897 BUCKET_BASE << 5,
1898 BUCKET_BASE << 6,
1899 BUCKET_BASE << 7,
1900 BUCKET_BASE << 8,
1901 BUCKET_BASE << 9,
1902 BUCKET_BASE << 10,
1903 BUCKET_BASE << 11,
1904 BUCKET_BASE << 12,
1905 BUCKET_BASE << 13,
1906 BUCKET_BASE << 14,
1907 BUCKET_BASE << 15,
1908 BUCKET_BASE << 16,
1909 BUCKET_BASE << 17,
1910 BUCKET_BASE << 18 /* 5,242,880us */
1911 };
1912
1913 static void
cam_iosched_update(struct iop_stats * iop,sbintime_t sim_latency)1914 cam_iosched_update(struct iop_stats *iop, sbintime_t sim_latency)
1915 {
1916 sbintime_t y, deltasq, delta;
1917 int i;
1918
1919 /*
1920 * Keep counts for latency. We do it by power of two buckets.
1921 * This helps us spot outlier behavior obscured by averages.
1922 */
1923 for (i = 0; i < LAT_BUCKETS - 1; i++) {
1924 if (sim_latency < latencies[i]) {
1925 iop->latencies[i]++;
1926 break;
1927 }
1928 }
1929 if (i == LAT_BUCKETS - 1)
1930 iop->latencies[i]++; /* Put all > 8192ms values into the last bucket. */
1931
1932 /*
1933 * Classic exponentially decaying average with a tiny alpha
1934 * (2 ^ -alpha_bits). For more info see the NIST statistical
1935 * handbook.
1936 *
1937 * ema_t = y_t * alpha + ema_t-1 * (1 - alpha) [nist]
1938 * ema_t = y_t * alpha + ema_t-1 - alpha * ema_t-1
1939 * ema_t = alpha * y_t - alpha * ema_t-1 + ema_t-1
1940 * alpha = 1 / (1 << alpha_bits)
1941 * sub e == ema_t-1, b == 1/alpha (== 1 << alpha_bits), d == y_t - ema_t-1
1942 * = y_t/b - e/b + be/b
1943 * = (y_t - e + be) / b
1944 * = (e + d) / b
1945 *
1946 * Since alpha is a power of two, we can compute this w/o any mult or
1947 * division.
1948 *
1949 * Variance can also be computed. Usually, it would be expressed as follows:
1950 * diff_t = y_t - ema_t-1
1951 * emvar_t = (1 - alpha) * (emavar_t-1 + diff_t^2 * alpha)
1952 * = emavar_t-1 - alpha * emavar_t-1 + delta_t^2 * alpha - (delta_t * alpha)^2
1953 * sub b == 1/alpha (== 1 << alpha_bits), e == emavar_t-1, d = delta_t^2
1954 * = e - e/b + dd/b + dd/bb
1955 * = (bbe - be + bdd + dd) / bb
1956 * = (bbe + b(dd-e) + dd) / bb (which is expanded below bb = 1<<(2*alpha_bits))
1957 */
1958 /*
1959 * XXX possible numeric issues
1960 * o We assume right shifted integers do the right thing, since that's
1961 * implementation defined. You can change the right shifts to / (1LL << alpha).
1962 * o alpha_bits = 9 gives ema ceiling of 23 bits of seconds for ema and 14 bits
1963 * for emvar. This puts a ceiling of 13 bits on alpha since we need a
1964 * few tens of seconds of representation.
1965 * o We mitigate alpha issues by never setting it too high.
1966 */
1967 y = sim_latency;
1968 delta = (y - iop->ema); /* d */
1969 iop->ema = ((iop->ema << alpha_bits) + delta) >> alpha_bits;
1970
1971 /*
1972 * Were we to naively plow ahead at this point, we wind up with many numerical
1973 * issues making any SD > ~3ms unreliable. So, we shift right by 12. This leaves
1974 * us with microsecond level precision in the input, so the same in the
1975 * output. It means we can't overflow deltasq unless delta > 4k seconds. It
1976 * also means that emvar can be up 46 bits 40 of which are fraction, which
1977 * gives us a way to measure up to ~8s in the SD before the computation goes
1978 * unstable. Even the worst hard disk rarely has > 1s service time in the
1979 * drive. It does mean we have to shift left 12 bits after taking the
1980 * square root to compute the actual standard deviation estimate. This loss of
1981 * precision is preferable to needing int128 types to work. The above numbers
1982 * assume alpha=9. 10 or 11 are ok, but we start to run into issues at 12,
1983 * so 12 or 13 is OK for EMA, EMVAR and SD will be wrong in those cases.
1984 */
1985 delta >>= 12;
1986 deltasq = delta * delta; /* dd */
1987 iop->emvar = ((iop->emvar << (2 * alpha_bits)) + /* bbe */
1988 ((deltasq - iop->emvar) << alpha_bits) + /* b(dd-e) */
1989 deltasq) /* dd */
1990 >> (2 * alpha_bits); /* div bb */
1991 iop->sd = (sbintime_t)isqrt64((uint64_t)iop->emvar) << 12;
1992 }
1993
1994 static void
cam_iosched_io_metric_update(struct cam_iosched_softc * isc,sbintime_t sim_latency,int cmd,size_t size)1995 cam_iosched_io_metric_update(struct cam_iosched_softc *isc,
1996 sbintime_t sim_latency, int cmd, size_t size)
1997 {
1998 /* xxx Do we need to scale based on the size of the I/O ? */
1999 switch (cmd) {
2000 case BIO_READ:
2001 cam_iosched_update(&isc->read_stats, sim_latency);
2002 break;
2003 case BIO_WRITE:
2004 cam_iosched_update(&isc->write_stats, sim_latency);
2005 break;
2006 case BIO_DELETE:
2007 cam_iosched_update(&isc->trim_stats, sim_latency);
2008 break;
2009 default:
2010 break;
2011 }
2012 }
2013
2014 #ifdef DDB
biolen(struct bio_queue_head * bq)2015 static int biolen(struct bio_queue_head *bq)
2016 {
2017 int i = 0;
2018 struct bio *bp;
2019
2020 TAILQ_FOREACH(bp, &bq->queue, bio_queue) {
2021 i++;
2022 }
2023 return i;
2024 }
2025
2026 /*
2027 * Show the internal state of the I/O scheduler.
2028 */
DB_SHOW_COMMAND(iosched,cam_iosched_db_show)2029 DB_SHOW_COMMAND(iosched, cam_iosched_db_show)
2030 {
2031 struct cam_iosched_softc *isc;
2032
2033 if (!have_addr) {
2034 db_printf("Need addr\n");
2035 return;
2036 }
2037 isc = (struct cam_iosched_softc *)addr;
2038 db_printf("pending_reads: %d\n", isc->read_stats.pending);
2039 db_printf("min_reads: %d\n", isc->read_stats.min);
2040 db_printf("max_reads: %d\n", isc->read_stats.max);
2041 db_printf("reads: %d\n", isc->read_stats.total);
2042 db_printf("in_reads: %d\n", isc->read_stats.in);
2043 db_printf("out_reads: %d\n", isc->read_stats.out);
2044 db_printf("queued_reads: %d\n", isc->read_stats.queued);
2045 db_printf("Read Q len %d\n", biolen(&isc->bio_queue));
2046 db_printf("pending_writes: %d\n", isc->write_stats.pending);
2047 db_printf("min_writes: %d\n", isc->write_stats.min);
2048 db_printf("max_writes: %d\n", isc->write_stats.max);
2049 db_printf("writes: %d\n", isc->write_stats.total);
2050 db_printf("in_writes: %d\n", isc->write_stats.in);
2051 db_printf("out_writes: %d\n", isc->write_stats.out);
2052 db_printf("queued_writes: %d\n", isc->write_stats.queued);
2053 db_printf("Write Q len %d\n", biolen(&isc->write_queue));
2054 db_printf("pending_trims: %d\n", isc->trim_stats.pending);
2055 db_printf("min_trims: %d\n", isc->trim_stats.min);
2056 db_printf("max_trims: %d\n", isc->trim_stats.max);
2057 db_printf("trims: %d\n", isc->trim_stats.total);
2058 db_printf("in_trims: %d\n", isc->trim_stats.in);
2059 db_printf("out_trims: %d\n", isc->trim_stats.out);
2060 db_printf("queued_trims: %d\n", isc->trim_stats.queued);
2061 db_printf("Trim Q len %d\n", biolen(&isc->trim_queue));
2062 db_printf("read_bias: %d\n", isc->read_bias);
2063 db_printf("current_read_bias: %d\n", isc->current_read_bias);
2064 db_printf("Trim active? %s\n",
2065 (isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) ? "yes" : "no");
2066 }
2067 #endif
2068 #endif
2069