FreeBSD/Linux Kernel Cross Reference
sys/cam/cam_iosched.c
1 /*-
2 * CAM IO Scheduler Interface
3 *
4 * Copyright (c) 2015 Netflix, Inc.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions, and the following disclaimer,
12 * without modification, immediately at the beginning of the file.
13 * 2. The name of the author may not be used to endorse or promote products
14 * derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
20 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * $FreeBSD: releng/11.0/sys/cam/cam_iosched.c 302396 2016-07-07 20:31:35Z imp $
29 */
30
31 #include "opt_cam.h"
32 #include "opt_ddb.h"
33
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD: releng/11.0/sys/cam/cam_iosched.c 302396 2016-07-07 20:31:35Z imp $");
36
37 #include <sys/param.h>
38
39 #include <sys/systm.h>
40 #include <sys/kernel.h>
41 #include <sys/bio.h>
42 #include <sys/lock.h>
43 #include <sys/malloc.h>
44 #include <sys/mutex.h>
45 #include <sys/sysctl.h>
46
47 #include <cam/cam.h>
48 #include <cam/cam_ccb.h>
49 #include <cam/cam_periph.h>
50 #include <cam/cam_xpt_periph.h>
51 #include <cam/cam_iosched.h>
52
53 #include <ddb/ddb.h>
54
55 static MALLOC_DEFINE(M_CAMSCHED, "CAM I/O Scheduler",
56 "CAM I/O Scheduler buffers");
57
58 /*
59 * Default I/O scheduler for FreeBSD. This implementation is just a thin-vineer
60 * over the bioq_* interface, with notions of separate calls for normal I/O and
61 * for trims.
62 *
63 * When CAM_IOSCHED_DYNAMIC is defined, the scheduler is enhanced to dynamically
64 * steer the rate of one type of traffic to help other types of traffic (eg
65 * limit writes when read latency deteriorates on SSDs).
66 */
67
68 #ifdef CAM_IOSCHED_DYNAMIC
69
70 static int do_dynamic_iosched = 1;
71 TUNABLE_INT("kern.cam.do_dynamic_iosched", &do_dynamic_iosched);
72 SYSCTL_INT(_kern_cam, OID_AUTO, do_dynamic_iosched, CTLFLAG_RD,
73 &do_dynamic_iosched, 1,
74 "Enable Dynamic I/O scheduler optimizations.");
75
76 static int alpha_bits = 9;
77 TUNABLE_INT("kern.cam.iosched_alpha_bits", &alpha_bits);
78 SYSCTL_INT(_kern_cam, OID_AUTO, iosched_alpha_bits, CTLFLAG_RW,
79 &alpha_bits, 1,
80 "Bits in EMA's alpha.");
81
82
83
84 struct iop_stats;
85 struct cam_iosched_softc;
86
87 int iosched_debug = 0;
88
89 typedef enum {
90 none = 0, /* No limits */
91 queue_depth, /* Limit how many ops we queue to SIM */
92 iops, /* Limit # of IOPS to the drive */
93 bandwidth, /* Limit bandwidth to the drive */
94 limiter_max
95 } io_limiter;
96
97 static const char *cam_iosched_limiter_names[] =
98 { "none", "queue_depth", "iops", "bandwidth" };
99
100 /*
101 * Called to initialize the bits of the iop_stats structure relevant to the
102 * limiter. Called just after the limiter is set.
103 */
104 typedef int l_init_t(struct iop_stats *);
105
106 /*
107 * Called every tick.
108 */
109 typedef int l_tick_t(struct iop_stats *);
110
111 /*
112 * Called to see if the limiter thinks this IOP can be allowed to
113 * proceed. If so, the limiter assumes that the while IOP proceeded
114 * and makes any accounting of it that's needed.
115 */
116 typedef int l_iop_t(struct iop_stats *, struct bio *);
117
118 /*
119 * Called when an I/O completes so the limiter can updates its
120 * accounting. Pending I/Os may complete in any order (even when
121 * sent to the hardware at the same time), so the limiter may not
122 * make any assumptions other than this I/O has completed. If it
123 * returns 1, then xpt_schedule() needs to be called again.
124 */
125 typedef int l_iodone_t(struct iop_stats *, struct bio *);
126
127 static l_iop_t cam_iosched_qd_iop;
128 static l_iop_t cam_iosched_qd_caniop;
129 static l_iodone_t cam_iosched_qd_iodone;
130
131 static l_init_t cam_iosched_iops_init;
132 static l_tick_t cam_iosched_iops_tick;
133 static l_iop_t cam_iosched_iops_caniop;
134 static l_iop_t cam_iosched_iops_iop;
135
136 static l_init_t cam_iosched_bw_init;
137 static l_tick_t cam_iosched_bw_tick;
138 static l_iop_t cam_iosched_bw_caniop;
139 static l_iop_t cam_iosched_bw_iop;
140
141 struct limswitch
142 {
143 l_init_t *l_init;
144 l_tick_t *l_tick;
145 l_iop_t *l_iop;
146 l_iop_t *l_caniop;
147 l_iodone_t *l_iodone;
148 } limsw[] =
149 {
150 { /* none */
151 .l_init = NULL,
152 .l_tick = NULL,
153 .l_iop = NULL,
154 .l_iodone= NULL,
155 },
156 { /* queue_depth */
157 .l_init = NULL,
158 .l_tick = NULL,
159 .l_caniop = cam_iosched_qd_caniop,
160 .l_iop = cam_iosched_qd_iop,
161 .l_iodone= cam_iosched_qd_iodone,
162 },
163 { /* iops */
164 .l_init = cam_iosched_iops_init,
165 .l_tick = cam_iosched_iops_tick,
166 .l_caniop = cam_iosched_iops_caniop,
167 .l_iop = cam_iosched_iops_iop,
168 .l_iodone= NULL,
169 },
170 { /* bandwidth */
171 .l_init = cam_iosched_bw_init,
172 .l_tick = cam_iosched_bw_tick,
173 .l_caniop = cam_iosched_bw_caniop,
174 .l_iop = cam_iosched_bw_iop,
175 .l_iodone= NULL,
176 },
177 };
178
179 struct iop_stats
180 {
181 /*
182 * sysctl state for this subnode.
183 */
184 struct sysctl_ctx_list sysctl_ctx;
185 struct sysctl_oid *sysctl_tree;
186
187 /*
188 * Information about the current rate limiters, if any
189 */
190 io_limiter limiter; /* How are I/Os being limited */
191 int min; /* Low range of limit */
192 int max; /* High range of limit */
193 int current; /* Current rate limiter */
194 int l_value1; /* per-limiter scratch value 1. */
195 int l_value2; /* per-limiter scratch value 2. */
196
197
198 /*
199 * Debug information about counts of I/Os that have gone through the
200 * scheduler.
201 */
202 int pending; /* I/Os pending in the hardware */
203 int queued; /* number currently in the queue */
204 int total; /* Total for all time -- wraps */
205 int in; /* number queued all time -- wraps */
206 int out; /* number completed all time -- wraps */
207
208 /*
209 * Statistics on different bits of the process.
210 */
211 /* Exp Moving Average, alpha = 1 / (1 << alpha_bits) */
212 sbintime_t ema;
213 sbintime_t emss; /* Exp Moving sum of the squares */
214 sbintime_t sd; /* Last computed sd */
215
216 struct cam_iosched_softc *softc;
217 };
218
219
220 typedef enum {
221 set_max = 0, /* current = max */
222 read_latency, /* Steer read latency by throttling writes */
223 cl_max /* Keep last */
224 } control_type;
225
226 static const char *cam_iosched_control_type_names[] =
227 { "set_max", "read_latency" };
228
229 struct control_loop
230 {
231 /*
232 * sysctl state for this subnode.
233 */
234 struct sysctl_ctx_list sysctl_ctx;
235 struct sysctl_oid *sysctl_tree;
236
237 sbintime_t next_steer; /* Time of next steer */
238 sbintime_t steer_interval; /* How often do we steer? */
239 sbintime_t lolat;
240 sbintime_t hilat;
241 int alpha;
242 control_type type; /* What type of control? */
243 int last_count; /* Last I/O count */
244
245 struct cam_iosched_softc *softc;
246 };
247
248 #endif
249
250 struct cam_iosched_softc
251 {
252 struct bio_queue_head bio_queue;
253 struct bio_queue_head trim_queue;
254 /* scheduler flags < 16, user flags >= 16 */
255 uint32_t flags;
256 int sort_io_queue;
257 #ifdef CAM_IOSCHED_DYNAMIC
258 int read_bias; /* Read bias setting */
259 int current_read_bias; /* Current read bias state */
260 int total_ticks;
261
262 struct bio_queue_head write_queue;
263 struct iop_stats read_stats, write_stats, trim_stats;
264 struct sysctl_ctx_list sysctl_ctx;
265 struct sysctl_oid *sysctl_tree;
266
267 int quanta; /* Number of quanta per second */
268 struct callout ticker; /* Callout for our quota system */
269 struct cam_periph *periph; /* cam periph associated with this device */
270 uint32_t this_frac; /* Fraction of a second (1024ths) for this tick */
271 sbintime_t last_time; /* Last time we ticked */
272 struct control_loop cl;
273 #endif
274 };
275
276 #ifdef CAM_IOSCHED_DYNAMIC
277 /*
278 * helper functions to call the limsw functions.
279 */
280 static int
281 cam_iosched_limiter_init(struct iop_stats *ios)
282 {
283 int lim = ios->limiter;
284
285 /* maybe this should be a kassert */
286 if (lim < none || lim >= limiter_max)
287 return EINVAL;
288
289 if (limsw[lim].l_init)
290 return limsw[lim].l_init(ios);
291
292 return 0;
293 }
294
295 static int
296 cam_iosched_limiter_tick(struct iop_stats *ios)
297 {
298 int lim = ios->limiter;
299
300 /* maybe this should be a kassert */
301 if (lim < none || lim >= limiter_max)
302 return EINVAL;
303
304 if (limsw[lim].l_tick)
305 return limsw[lim].l_tick(ios);
306
307 return 0;
308 }
309
310 static int
311 cam_iosched_limiter_iop(struct iop_stats *ios, struct bio *bp)
312 {
313 int lim = ios->limiter;
314
315 /* maybe this should be a kassert */
316 if (lim < none || lim >= limiter_max)
317 return EINVAL;
318
319 if (limsw[lim].l_iop)
320 return limsw[lim].l_iop(ios, bp);
321
322 return 0;
323 }
324
325 static int
326 cam_iosched_limiter_caniop(struct iop_stats *ios, struct bio *bp)
327 {
328 int lim = ios->limiter;
329
330 /* maybe this should be a kassert */
331 if (lim < none || lim >= limiter_max)
332 return EINVAL;
333
334 if (limsw[lim].l_caniop)
335 return limsw[lim].l_caniop(ios, bp);
336
337 return 0;
338 }
339
340 static int
341 cam_iosched_limiter_iodone(struct iop_stats *ios, struct bio *bp)
342 {
343 int lim = ios->limiter;
344
345 /* maybe this should be a kassert */
346 if (lim < none || lim >= limiter_max)
347 return 0;
348
349 if (limsw[lim].l_iodone)
350 return limsw[lim].l_iodone(ios, bp);
351
352 return 0;
353 }
354
355 /*
356 * Functions to implement the different kinds of limiters
357 */
358
359 static int
360 cam_iosched_qd_iop(struct iop_stats *ios, struct bio *bp)
361 {
362
363 if (ios->current <= 0 || ios->pending < ios->current)
364 return 0;
365
366 return EAGAIN;
367 }
368
369 static int
370 cam_iosched_qd_caniop(struct iop_stats *ios, struct bio *bp)
371 {
372
373 if (ios->current <= 0 || ios->pending < ios->current)
374 return 0;
375
376 return EAGAIN;
377 }
378
379 static int
380 cam_iosched_qd_iodone(struct iop_stats *ios, struct bio *bp)
381 {
382
383 if (ios->current <= 0 || ios->pending != ios->current)
384 return 0;
385
386 return 1;
387 }
388
389 static int
390 cam_iosched_iops_init(struct iop_stats *ios)
391 {
392
393 ios->l_value1 = ios->current / ios->softc->quanta;
394 if (ios->l_value1 <= 0)
395 ios->l_value1 = 1;
396
397 return 0;
398 }
399
400 static int
401 cam_iosched_iops_tick(struct iop_stats *ios)
402 {
403
404 ios->l_value1 = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16);
405 if (ios->l_value1 <= 0)
406 ios->l_value1 = 1;
407
408 return 0;
409 }
410
411 static int
412 cam_iosched_iops_caniop(struct iop_stats *ios, struct bio *bp)
413 {
414
415 /*
416 * So if we have any more IOPs left, allow it,
417 * otherwise wait.
418 */
419 if (ios->l_value1 <= 0)
420 return EAGAIN;
421 return 0;
422 }
423
424 static int
425 cam_iosched_iops_iop(struct iop_stats *ios, struct bio *bp)
426 {
427 int rv;
428
429 rv = cam_iosched_limiter_caniop(ios, bp);
430 if (rv == 0)
431 ios->l_value1--;
432
433 return rv;
434 }
435
436 static int
437 cam_iosched_bw_init(struct iop_stats *ios)
438 {
439
440 /* ios->current is in kB/s, so scale to bytes */
441 ios->l_value1 = ios->current * 1000 / ios->softc->quanta;
442
443 return 0;
444 }
445
446 static int
447 cam_iosched_bw_tick(struct iop_stats *ios)
448 {
449 int bw;
450
451 /*
452 * If we're in the hole for available quota from
453 * the last time, then add the quantum for this.
454 * If we have any left over from last quantum,
455 * then too bad, that's lost. Also, ios->current
456 * is in kB/s, so scale.
457 *
458 * We also allow up to 4 quanta of credits to
459 * accumulate to deal with burstiness. 4 is extremely
460 * arbitrary.
461 */
462 bw = (int)((ios->current * 1000ull * (uint64_t)ios->softc->this_frac) >> 16);
463 if (ios->l_value1 < bw * 4)
464 ios->l_value1 += bw;
465
466 return 0;
467 }
468
469 static int
470 cam_iosched_bw_caniop(struct iop_stats *ios, struct bio *bp)
471 {
472 /*
473 * So if we have any more bw quota left, allow it,
474 * otherwise wait. Not, we'll go negative and that's
475 * OK. We'll just get a lettle less next quota.
476 *
477 * Note on going negative: that allows us to process
478 * requests in order better, since we won't allow
479 * shorter reads to get around the long one that we
480 * don't have the quota to do just yet. It also prevents
481 * starvation by being a little more permissive about
482 * what we let through this quantum (to prevent the
483 * starvation), at the cost of getting a little less
484 * next quantum.
485 */
486 if (ios->l_value1 <= 0)
487 return EAGAIN;
488
489
490 return 0;
491 }
492
493 static int
494 cam_iosched_bw_iop(struct iop_stats *ios, struct bio *bp)
495 {
496 int rv;
497
498 rv = cam_iosched_limiter_caniop(ios, bp);
499 if (rv == 0)
500 ios->l_value1 -= bp->bio_length;
501
502 return rv;
503 }
504
505 static void cam_iosched_cl_maybe_steer(struct control_loop *clp);
506
507 static void
508 cam_iosched_ticker(void *arg)
509 {
510 struct cam_iosched_softc *isc = arg;
511 sbintime_t now, delta;
512
513 callout_reset(&isc->ticker, hz / isc->quanta - 1, cam_iosched_ticker, isc);
514
515 now = sbinuptime();
516 delta = now - isc->last_time;
517 isc->this_frac = (uint32_t)delta >> 16; /* Note: discards seconds -- should be 0 harmless if not */
518 isc->last_time = now;
519
520 cam_iosched_cl_maybe_steer(&isc->cl);
521
522 cam_iosched_limiter_tick(&isc->read_stats);
523 cam_iosched_limiter_tick(&isc->write_stats);
524 cam_iosched_limiter_tick(&isc->trim_stats);
525
526 cam_iosched_schedule(isc, isc->periph);
527
528 isc->total_ticks++;
529 }
530
531
532 static void
533 cam_iosched_cl_init(struct control_loop *clp, struct cam_iosched_softc *isc)
534 {
535
536 clp->next_steer = sbinuptime();
537 clp->softc = isc;
538 clp->steer_interval = SBT_1S * 5; /* Let's start out steering every 5s */
539 clp->lolat = 5 * SBT_1MS;
540 clp->hilat = 15 * SBT_1MS;
541 clp->alpha = 20; /* Alpha == gain. 20 = .2 */
542 clp->type = set_max;
543 }
544
545 static void
546 cam_iosched_cl_maybe_steer(struct control_loop *clp)
547 {
548 struct cam_iosched_softc *isc;
549 sbintime_t now, lat;
550 int old;
551
552 isc = clp->softc;
553 now = isc->last_time;
554 if (now < clp->next_steer)
555 return;
556
557 clp->next_steer = now + clp->steer_interval;
558 switch (clp->type) {
559 case set_max:
560 if (isc->write_stats.current != isc->write_stats.max)
561 printf("Steering write from %d kBps to %d kBps\n",
562 isc->write_stats.current, isc->write_stats.max);
563 isc->read_stats.current = isc->read_stats.max;
564 isc->write_stats.current = isc->write_stats.max;
565 isc->trim_stats.current = isc->trim_stats.max;
566 break;
567 case read_latency:
568 old = isc->write_stats.current;
569 lat = isc->read_stats.ema;
570 /*
571 * Simple PLL-like engine. Since we're steering to a range for
572 * the SP (set point) that makes things a little more
573 * complicated. In addition, we're not directly controlling our
574 * PV (process variable), the read latency, but instead are
575 * manipulating the write bandwidth limit for our MV
576 * (manipulation variable), analysis of this code gets a bit
577 * messy. Also, the MV is a very noisy control surface for read
578 * latency since it is affected by many hidden processes inside
579 * the device which change how responsive read latency will be
580 * in reaction to changes in write bandwidth. Unlike the classic
581 * boiler control PLL. this may result in over-steering while
582 * the SSD takes its time to react to the new, lower load. This
583 * is why we use a relatively low alpha of between .1 and .25 to
584 * compensate for this effect. At .1, it takes ~22 steering
585 * intervals to back off by a factor of 10. At .2 it only takes
586 * ~10. At .25 it only takes ~8. However some preliminary data
587 * from the SSD drives suggests a reasponse time in 10's of
588 * seconds before latency drops regardless of the new write
589 * rate. Careful observation will be reqiured to tune this
590 * effectively.
591 *
592 * Also, when there's no read traffic, we jack up the write
593 * limit too regardless of the last read latency. 10 is
594 * somewhat arbitrary.
595 */
596 if (lat < clp->lolat || isc->read_stats.total - clp->last_count < 10)
597 isc->write_stats.current = isc->write_stats.current *
598 (100 + clp->alpha) / 100; /* Scale up */
599 else if (lat > clp->hilat)
600 isc->write_stats.current = isc->write_stats.current *
601 (100 - clp->alpha) / 100; /* Scale down */
602 clp->last_count = isc->read_stats.total;
603
604 /*
605 * Even if we don't steer, per se, enforce the min/max limits as
606 * those may have changed.
607 */
608 if (isc->write_stats.current < isc->write_stats.min)
609 isc->write_stats.current = isc->write_stats.min;
610 if (isc->write_stats.current > isc->write_stats.max)
611 isc->write_stats.current = isc->write_stats.max;
612 if (old != isc->write_stats.current && iosched_debug)
613 printf("Steering write from %d kBps to %d kBps due to latency of %jdms\n",
614 old, isc->write_stats.current,
615 (uintmax_t)((uint64_t)1000000 * (uint32_t)lat) >> 32);
616 break;
617 case cl_max:
618 break;
619 }
620 }
621 #endif
622
623 /* Trim or similar currently pending completion */
624 #define CAM_IOSCHED_FLAG_TRIM_ACTIVE (1ul << 0)
625 /* Callout active, and needs to be torn down */
626 #define CAM_IOSCHED_FLAG_CALLOUT_ACTIVE (1ul << 1)
627
628 /* Periph drivers set these flags to indicate work */
629 #define CAM_IOSCHED_FLAG_WORK_FLAGS ((0xffffu) << 16)
630
631 #ifdef CAM_IOSCHED_DYNAMIC
632 static void
633 cam_iosched_io_metric_update(struct cam_iosched_softc *isc,
634 sbintime_t sim_latency, int cmd, size_t size);
635 #endif
636
637 static inline int
638 cam_iosched_has_flagged_work(struct cam_iosched_softc *isc)
639 {
640 return !!(isc->flags & CAM_IOSCHED_FLAG_WORK_FLAGS);
641 }
642
643 static inline int
644 cam_iosched_has_io(struct cam_iosched_softc *isc)
645 {
646 #ifdef CAM_IOSCHED_DYNAMIC
647 if (do_dynamic_iosched) {
648 struct bio *rbp = bioq_first(&isc->bio_queue);
649 struct bio *wbp = bioq_first(&isc->write_queue);
650 int can_write = wbp != NULL &&
651 cam_iosched_limiter_caniop(&isc->write_stats, wbp) == 0;
652 int can_read = rbp != NULL &&
653 cam_iosched_limiter_caniop(&isc->read_stats, rbp) == 0;
654 if (iosched_debug > 2) {
655 printf("can write %d: pending_writes %d max_writes %d\n", can_write, isc->write_stats.pending, isc->write_stats.max);
656 printf("can read %d: read_stats.pending %d max_reads %d\n", can_read, isc->read_stats.pending, isc->read_stats.max);
657 printf("Queued reads %d writes %d\n", isc->read_stats.queued, isc->write_stats.queued);
658 }
659 return can_read || can_write;
660 }
661 #endif
662 return bioq_first(&isc->bio_queue) != NULL;
663 }
664
665 static inline int
666 cam_iosched_has_more_trim(struct cam_iosched_softc *isc)
667 {
668 return !(isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) &&
669 bioq_first(&isc->trim_queue);
670 }
671
672 #define cam_iosched_sort_queue(isc) ((isc)->sort_io_queue >= 0 ? \
673 (isc)->sort_io_queue : cam_sort_io_queues)
674
675
676 static inline int
677 cam_iosched_has_work(struct cam_iosched_softc *isc)
678 {
679 #ifdef CAM_IOSCHED_DYNAMIC
680 if (iosched_debug > 2)
681 printf("has work: %d %d %d\n", cam_iosched_has_io(isc),
682 cam_iosched_has_more_trim(isc),
683 cam_iosched_has_flagged_work(isc));
684 #endif
685
686 return cam_iosched_has_io(isc) ||
687 cam_iosched_has_more_trim(isc) ||
688 cam_iosched_has_flagged_work(isc);
689 }
690
691 #ifdef CAM_IOSCHED_DYNAMIC
692 static void
693 cam_iosched_iop_stats_init(struct cam_iosched_softc *isc, struct iop_stats *ios)
694 {
695
696 ios->limiter = none;
697 cam_iosched_limiter_init(ios);
698 ios->in = 0;
699 ios->max = 300000;
700 ios->min = 1;
701 ios->out = 0;
702 ios->pending = 0;
703 ios->queued = 0;
704 ios->total = 0;
705 ios->ema = 0;
706 ios->emss = 0;
707 ios->sd = 0;
708 ios->softc = isc;
709 }
710
711 static int
712 cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS)
713 {
714 char buf[16];
715 struct iop_stats *ios;
716 struct cam_iosched_softc *isc;
717 int value, i, error, cantick;
718 const char *p;
719
720 ios = arg1;
721 isc = ios->softc;
722 value = ios->limiter;
723 if (value < none || value >= limiter_max)
724 p = "UNKNOWN";
725 else
726 p = cam_iosched_limiter_names[value];
727
728 strlcpy(buf, p, sizeof(buf));
729 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
730 if (error != 0 || req->newptr == NULL)
731 return error;
732
733 cam_periph_lock(isc->periph);
734
735 for (i = none; i < limiter_max; i++) {
736 if (strcmp(buf, cam_iosched_limiter_names[i]) != 0)
737 continue;
738 ios->limiter = i;
739 error = cam_iosched_limiter_init(ios);
740 if (error != 0) {
741 ios->limiter = value;
742 cam_periph_unlock(isc->periph);
743 return error;
744 }
745 cantick = !!limsw[isc->read_stats.limiter].l_tick +
746 !!limsw[isc->write_stats.limiter].l_tick +
747 !!limsw[isc->trim_stats.limiter].l_tick +
748 1; /* Control loop requires it */
749 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) {
750 if (cantick == 0) {
751 callout_stop(&isc->ticker);
752 isc->flags &= ~CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
753 }
754 } else {
755 if (cantick != 0) {
756 callout_reset(&isc->ticker, hz / isc->quanta - 1, cam_iosched_ticker, isc);
757 isc->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
758 }
759 }
760
761 cam_periph_unlock(isc->periph);
762 return 0;
763 }
764
765 cam_periph_unlock(isc->periph);
766 return EINVAL;
767 }
768
769 static int
770 cam_iosched_control_type_sysctl(SYSCTL_HANDLER_ARGS)
771 {
772 char buf[16];
773 struct control_loop *clp;
774 struct cam_iosched_softc *isc;
775 int value, i, error;
776 const char *p;
777
778 clp = arg1;
779 isc = clp->softc;
780 value = clp->type;
781 if (value < none || value >= cl_max)
782 p = "UNKNOWN";
783 else
784 p = cam_iosched_control_type_names[value];
785
786 strlcpy(buf, p, sizeof(buf));
787 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
788 if (error != 0 || req->newptr == NULL)
789 return error;
790
791 for (i = set_max; i < cl_max; i++) {
792 if (strcmp(buf, cam_iosched_control_type_names[i]) != 0)
793 continue;
794 cam_periph_lock(isc->periph);
795 clp->type = i;
796 cam_periph_unlock(isc->periph);
797 return 0;
798 }
799
800 return EINVAL;
801 }
802
803 static int
804 cam_iosched_sbintime_sysctl(SYSCTL_HANDLER_ARGS)
805 {
806 char buf[16];
807 sbintime_t value;
808 int error;
809 uint64_t us;
810
811 value = *(sbintime_t *)arg1;
812 us = (uint64_t)value / SBT_1US;
813 snprintf(buf, sizeof(buf), "%ju", (intmax_t)us);
814 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
815 if (error != 0 || req->newptr == NULL)
816 return error;
817 us = strtoul(buf, NULL, 10);
818 if (us == 0)
819 return EINVAL;
820 *(sbintime_t *)arg1 = us * SBT_1US;
821 return 0;
822 }
823
824 static void
825 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct iop_stats *ios, char *name)
826 {
827 struct sysctl_oid_list *n;
828 struct sysctl_ctx_list *ctx;
829
830 ios->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx,
831 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, name,
832 CTLFLAG_RD, 0, name);
833 n = SYSCTL_CHILDREN(ios->sysctl_tree);
834 ctx = &ios->sysctl_ctx;
835
836 SYSCTL_ADD_UQUAD(ctx, n,
837 OID_AUTO, "ema", CTLFLAG_RD,
838 &ios->ema,
839 "Fast Exponentially Weighted Moving Average");
840 SYSCTL_ADD_UQUAD(ctx, n,
841 OID_AUTO, "emss", CTLFLAG_RD,
842 &ios->emss,
843 "Fast Exponentially Weighted Moving Sum of Squares (maybe wrong)");
844 SYSCTL_ADD_UQUAD(ctx, n,
845 OID_AUTO, "sd", CTLFLAG_RD,
846 &ios->sd,
847 "Estimated SD for fast ema (may be wrong)");
848
849 SYSCTL_ADD_INT(ctx, n,
850 OID_AUTO, "pending", CTLFLAG_RD,
851 &ios->pending, 0,
852 "Instantaneous # of pending transactions");
853 SYSCTL_ADD_INT(ctx, n,
854 OID_AUTO, "count", CTLFLAG_RD,
855 &ios->total, 0,
856 "# of transactions submitted to hardware");
857 SYSCTL_ADD_INT(ctx, n,
858 OID_AUTO, "queued", CTLFLAG_RD,
859 &ios->queued, 0,
860 "# of transactions in the queue");
861 SYSCTL_ADD_INT(ctx, n,
862 OID_AUTO, "in", CTLFLAG_RD,
863 &ios->in, 0,
864 "# of transactions queued to driver");
865 SYSCTL_ADD_INT(ctx, n,
866 OID_AUTO, "out", CTLFLAG_RD,
867 &ios->out, 0,
868 "# of transactions completed");
869
870 SYSCTL_ADD_PROC(ctx, n,
871 OID_AUTO, "limiter", CTLTYPE_STRING | CTLFLAG_RW,
872 ios, 0, cam_iosched_limiter_sysctl, "A",
873 "Current limiting type.");
874 SYSCTL_ADD_INT(ctx, n,
875 OID_AUTO, "min", CTLFLAG_RW,
876 &ios->min, 0,
877 "min resource");
878 SYSCTL_ADD_INT(ctx, n,
879 OID_AUTO, "max", CTLFLAG_RW,
880 &ios->max, 0,
881 "max resource");
882 SYSCTL_ADD_INT(ctx, n,
883 OID_AUTO, "current", CTLFLAG_RW,
884 &ios->current, 0,
885 "current resource");
886
887 }
888
889 static void
890 cam_iosched_iop_stats_fini(struct iop_stats *ios)
891 {
892 if (ios->sysctl_tree)
893 if (sysctl_ctx_free(&ios->sysctl_ctx) != 0)
894 printf("can't remove iosched sysctl stats context\n");
895 }
896
897 static void
898 cam_iosched_cl_sysctl_init(struct cam_iosched_softc *isc)
899 {
900 struct sysctl_oid_list *n;
901 struct sysctl_ctx_list *ctx;
902 struct control_loop *clp;
903
904 clp = &isc->cl;
905 clp->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx,
906 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, "control",
907 CTLFLAG_RD, 0, "Control loop info");
908 n = SYSCTL_CHILDREN(clp->sysctl_tree);
909 ctx = &clp->sysctl_ctx;
910
911 SYSCTL_ADD_PROC(ctx, n,
912 OID_AUTO, "type", CTLTYPE_STRING | CTLFLAG_RW,
913 clp, 0, cam_iosched_control_type_sysctl, "A",
914 "Control loop algorithm");
915 SYSCTL_ADD_PROC(ctx, n,
916 OID_AUTO, "steer_interval", CTLTYPE_STRING | CTLFLAG_RW,
917 &clp->steer_interval, 0, cam_iosched_sbintime_sysctl, "A",
918 "How often to steer (in us)");
919 SYSCTL_ADD_PROC(ctx, n,
920 OID_AUTO, "lolat", CTLTYPE_STRING | CTLFLAG_RW,
921 &clp->lolat, 0, cam_iosched_sbintime_sysctl, "A",
922 "Low water mark for Latency (in us)");
923 SYSCTL_ADD_PROC(ctx, n,
924 OID_AUTO, "hilat", CTLTYPE_STRING | CTLFLAG_RW,
925 &clp->hilat, 0, cam_iosched_sbintime_sysctl, "A",
926 "Hi water mark for Latency (in us)");
927 SYSCTL_ADD_INT(ctx, n,
928 OID_AUTO, "alpha", CTLFLAG_RW,
929 &clp->alpha, 0,
930 "Alpha for PLL (x100) aka gain");
931 }
932
933 static void
934 cam_iosched_cl_sysctl_fini(struct control_loop *clp)
935 {
936 if (clp->sysctl_tree)
937 if (sysctl_ctx_free(&clp->sysctl_ctx) != 0)
938 printf("can't remove iosched sysctl control loop context\n");
939 }
940 #endif
941
942 /*
943 * Allocate the iosched structure. This also insulates callers from knowing
944 * sizeof struct cam_iosched_softc.
945 */
946 int
947 cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph)
948 {
949
950 *iscp = malloc(sizeof(**iscp), M_CAMSCHED, M_NOWAIT | M_ZERO);
951 if (*iscp == NULL)
952 return ENOMEM;
953 #ifdef CAM_IOSCHED_DYNAMIC
954 if (iosched_debug)
955 printf("CAM IOSCHEDULER Allocating entry at %p\n", *iscp);
956 #endif
957 (*iscp)->sort_io_queue = -1;
958 bioq_init(&(*iscp)->bio_queue);
959 bioq_init(&(*iscp)->trim_queue);
960 #ifdef CAM_IOSCHED_DYNAMIC
961 if (do_dynamic_iosched) {
962 bioq_init(&(*iscp)->write_queue);
963 (*iscp)->read_bias = 100;
964 (*iscp)->current_read_bias = 100;
965 (*iscp)->quanta = 200;
966 cam_iosched_iop_stats_init(*iscp, &(*iscp)->read_stats);
967 cam_iosched_iop_stats_init(*iscp, &(*iscp)->write_stats);
968 cam_iosched_iop_stats_init(*iscp, &(*iscp)->trim_stats);
969 (*iscp)->trim_stats.max = 1; /* Trims are special: one at a time for now */
970 (*iscp)->last_time = sbinuptime();
971 callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0);
972 (*iscp)->periph = periph;
973 cam_iosched_cl_init(&(*iscp)->cl, *iscp);
974 callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta - 1, cam_iosched_ticker, *iscp);
975 (*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
976 }
977 #endif
978
979 return 0;
980 }
981
982 /*
983 * Reclaim all used resources. This assumes that other folks have
984 * drained the requests in the hardware. Maybe an unwise assumption.
985 */
986 void
987 cam_iosched_fini(struct cam_iosched_softc *isc)
988 {
989 if (isc) {
990 cam_iosched_flush(isc, NULL, ENXIO);
991 #ifdef CAM_IOSCHED_DYNAMIC
992 cam_iosched_iop_stats_fini(&isc->read_stats);
993 cam_iosched_iop_stats_fini(&isc->write_stats);
994 cam_iosched_iop_stats_fini(&isc->trim_stats);
995 cam_iosched_cl_sysctl_fini(&isc->cl);
996 if (isc->sysctl_tree)
997 if (sysctl_ctx_free(&isc->sysctl_ctx) != 0)
998 printf("can't remove iosched sysctl stats context\n");
999 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) {
1000 callout_drain(&isc->ticker);
1001 isc->flags &= ~ CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
1002 }
1003
1004 #endif
1005 free(isc, M_CAMSCHED);
1006 }
1007 }
1008
1009 /*
1010 * After we're sure we're attaching a device, go ahead and add
1011 * hooks for any sysctl we may wish to honor.
1012 */
1013 void cam_iosched_sysctl_init(struct cam_iosched_softc *isc,
1014 struct sysctl_ctx_list *ctx, struct sysctl_oid *node)
1015 {
1016 #ifdef CAM_IOSCHED_DYNAMIC
1017 struct sysctl_oid_list *n;
1018 #endif
1019
1020 SYSCTL_ADD_INT(ctx, SYSCTL_CHILDREN(node),
1021 OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE,
1022 &isc->sort_io_queue, 0,
1023 "Sort IO queue to try and optimise disk access patterns");
1024
1025 #ifdef CAM_IOSCHED_DYNAMIC
1026 if (!do_dynamic_iosched)
1027 return;
1028
1029 isc->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx,
1030 SYSCTL_CHILDREN(node), OID_AUTO, "iosched",
1031 CTLFLAG_RD, 0, "I/O scheduler statistics");
1032 n = SYSCTL_CHILDREN(isc->sysctl_tree);
1033 ctx = &isc->sysctl_ctx;
1034
1035 cam_iosched_iop_stats_sysctl_init(isc, &isc->read_stats, "read");
1036 cam_iosched_iop_stats_sysctl_init(isc, &isc->write_stats, "write");
1037 cam_iosched_iop_stats_sysctl_init(isc, &isc->trim_stats, "trim");
1038 cam_iosched_cl_sysctl_init(isc);
1039
1040 SYSCTL_ADD_INT(ctx, n,
1041 OID_AUTO, "read_bias", CTLFLAG_RW,
1042 &isc->read_bias, 100,
1043 "How biased towards read should we be independent of limits");
1044
1045 SYSCTL_ADD_INT(ctx, n,
1046 OID_AUTO, "quanta", CTLFLAG_RW,
1047 &isc->quanta, 200,
1048 "How many quanta per second do we slice the I/O up into");
1049
1050 SYSCTL_ADD_INT(ctx, n,
1051 OID_AUTO, "total_ticks", CTLFLAG_RD,
1052 &isc->total_ticks, 0,
1053 "Total number of ticks we've done");
1054 #endif
1055 }
1056
1057 /*
1058 * Flush outstanding I/O. Consumers of this library don't know all the
1059 * queues we may keep, so this allows all I/O to be flushed in one
1060 * convenient call.
1061 */
1062 void
1063 cam_iosched_flush(struct cam_iosched_softc *isc, struct devstat *stp, int err)
1064 {
1065 bioq_flush(&isc->bio_queue, stp, err);
1066 bioq_flush(&isc->trim_queue, stp, err);
1067 #ifdef CAM_IOSCHED_DYNAMIC
1068 if (do_dynamic_iosched)
1069 bioq_flush(&isc->write_queue, stp, err);
1070 #endif
1071 }
1072
1073 #ifdef CAM_IOSCHED_DYNAMIC
1074 static struct bio *
1075 cam_iosched_get_write(struct cam_iosched_softc *isc)
1076 {
1077 struct bio *bp;
1078
1079 /*
1080 * We control the write rate by controlling how many requests we send
1081 * down to the drive at any one time. Fewer requests limits the
1082 * effects of both starvation when the requests take a while and write
1083 * amplification when each request is causing more than one write to
1084 * the NAND media. Limiting the queue depth like this will also limit
1085 * the write throughput and give and reads that want to compete to
1086 * compete unfairly.
1087 */
1088 bp = bioq_first(&isc->write_queue);
1089 if (bp == NULL) {
1090 if (iosched_debug > 3)
1091 printf("No writes present in write_queue\n");
1092 return NULL;
1093 }
1094
1095 /*
1096 * If pending read, prefer that based on current read bias
1097 * setting.
1098 */
1099 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) {
1100 if (iosched_debug)
1101 printf("Reads present and current_read_bias is %d queued writes %d queued reads %d\n", isc->current_read_bias, isc->write_stats.queued, isc->read_stats.queued);
1102 isc->current_read_bias--;
1103 return NULL;
1104 }
1105
1106 /*
1107 * See if our current limiter allows this I/O.
1108 */
1109 if (cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) {
1110 if (iosched_debug)
1111 printf("Can't write because limiter says no.\n");
1112 return NULL;
1113 }
1114
1115 /*
1116 * Let's do this: We've passed all the gates and we're a go
1117 * to schedule the I/O in the SIM.
1118 */
1119 isc->current_read_bias = isc->read_bias;
1120 bioq_remove(&isc->write_queue, bp);
1121 if (bp->bio_cmd == BIO_WRITE) {
1122 isc->write_stats.queued--;
1123 isc->write_stats.total++;
1124 isc->write_stats.pending++;
1125 }
1126 if (iosched_debug > 9)
1127 printf("HWQ : %p %#x\n", bp, bp->bio_cmd);
1128 return bp;
1129 }
1130 #endif
1131
1132 /*
1133 * Put back a trim that you weren't able to actually schedule this time.
1134 */
1135 void
1136 cam_iosched_put_back_trim(struct cam_iosched_softc *isc, struct bio *bp)
1137 {
1138 bioq_insert_head(&isc->trim_queue, bp);
1139 #ifdef CAM_IOSCHED_DYNAMIC
1140 isc->trim_stats.queued++;
1141 isc->trim_stats.total--; /* since we put it back, don't double count */
1142 isc->trim_stats.pending--;
1143 #endif
1144 }
1145
1146 /*
1147 * gets the next trim from the trim queue.
1148 *
1149 * Assumes we're called with the periph lock held. It removes this
1150 * trim from the queue and the device must explicitly reinstert it
1151 * should the need arise.
1152 */
1153 struct bio *
1154 cam_iosched_next_trim(struct cam_iosched_softc *isc)
1155 {
1156 struct bio *bp;
1157
1158 bp = bioq_first(&isc->trim_queue);
1159 if (bp == NULL)
1160 return NULL;
1161 bioq_remove(&isc->trim_queue, bp);
1162 #ifdef CAM_IOSCHED_DYNAMIC
1163 isc->trim_stats.queued--;
1164 isc->trim_stats.total++;
1165 isc->trim_stats.pending++;
1166 #endif
1167 return bp;
1168 }
1169
1170 /*
1171 * gets the an available trim from the trim queue, if there's no trim
1172 * already pending. It removes this trim from the queue and the device
1173 * must explicitly reinstert it should the need arise.
1174 *
1175 * Assumes we're called with the periph lock held.
1176 */
1177 struct bio *
1178 cam_iosched_get_trim(struct cam_iosched_softc *isc)
1179 {
1180
1181 if (!cam_iosched_has_more_trim(isc))
1182 return NULL;
1183
1184 return cam_iosched_next_trim(isc);
1185 }
1186
1187 /*
1188 * Determine what the next bit of work to do is for the periph. The
1189 * default implementation looks to see if we have trims to do, but no
1190 * trims outstanding. If so, we do that. Otherwise we see if we have
1191 * other work. If we do, then we do that. Otherwise why were we called?
1192 */
1193 struct bio *
1194 cam_iosched_next_bio(struct cam_iosched_softc *isc)
1195 {
1196 struct bio *bp;
1197
1198 /*
1199 * See if we have a trim that can be scheduled. We can only send one
1200 * at a time down, so this takes that into account.
1201 *
1202 * XXX newer TRIM commands are queueable. Revisit this when we
1203 * implement them.
1204 */
1205 if ((bp = cam_iosched_get_trim(isc)) != NULL)
1206 return bp;
1207
1208 #ifdef CAM_IOSCHED_DYNAMIC
1209 /*
1210 * See if we have any pending writes, and room in the queue for them,
1211 * and if so, those are next.
1212 */
1213 if (do_dynamic_iosched) {
1214 if ((bp = cam_iosched_get_write(isc)) != NULL)
1215 return bp;
1216 }
1217 #endif
1218
1219 /*
1220 * next, see if there's other, normal I/O waiting. If so return that.
1221 */
1222 if ((bp = bioq_first(&isc->bio_queue)) == NULL)
1223 return NULL;
1224
1225 #ifdef CAM_IOSCHED_DYNAMIC
1226 /*
1227 * For the netflix scheduler, bio_queue is only for reads, so enforce
1228 * the limits here. Enforce only for reads.
1229 */
1230 if (do_dynamic_iosched) {
1231 if (bp->bio_cmd == BIO_READ &&
1232 cam_iosched_limiter_iop(&isc->read_stats, bp) != 0)
1233 return NULL;
1234 }
1235 #endif
1236 bioq_remove(&isc->bio_queue, bp);
1237 #ifdef CAM_IOSCHED_DYNAMIC
1238 if (do_dynamic_iosched) {
1239 if (bp->bio_cmd == BIO_READ) {
1240 isc->read_stats.queued--;
1241 isc->read_stats.total++;
1242 isc->read_stats.pending++;
1243 } else
1244 printf("Found bio_cmd = %#x\n", bp->bio_cmd);
1245 }
1246 if (iosched_debug > 9)
1247 printf("HWQ : %p %#x\n", bp, bp->bio_cmd);
1248 #endif
1249 return bp;
1250 }
1251
1252 /*
1253 * Driver has been given some work to do by the block layer. Tell the
1254 * scheduler about it and have it queue the work up. The scheduler module
1255 * will then return the currently most useful bit of work later, possibly
1256 * deferring work for various reasons.
1257 */
1258 void
1259 cam_iosched_queue_work(struct cam_iosched_softc *isc, struct bio *bp)
1260 {
1261
1262 /*
1263 * Put all trims on the trim queue sorted, since we know
1264 * that the collapsing code requires this. Otherwise put
1265 * the work on the bio queue.
1266 */
1267 if (bp->bio_cmd == BIO_DELETE) {
1268 bioq_disksort(&isc->trim_queue, bp);
1269 #ifdef CAM_IOSCHED_DYNAMIC
1270 isc->trim_stats.in++;
1271 isc->trim_stats.queued++;
1272 #endif
1273 }
1274 #ifdef CAM_IOSCHED_DYNAMIC
1275 else if (do_dynamic_iosched &&
1276 (bp->bio_cmd == BIO_WRITE || bp->bio_cmd == BIO_FLUSH)) {
1277 if (cam_iosched_sort_queue(isc))
1278 bioq_disksort(&isc->write_queue, bp);
1279 else
1280 bioq_insert_tail(&isc->write_queue, bp);
1281 if (iosched_debug > 9)
1282 printf("Qw : %p %#x\n", bp, bp->bio_cmd);
1283 if (bp->bio_cmd == BIO_WRITE) {
1284 isc->write_stats.in++;
1285 isc->write_stats.queued++;
1286 }
1287 }
1288 #endif
1289 else {
1290 if (cam_iosched_sort_queue(isc))
1291 bioq_disksort(&isc->bio_queue, bp);
1292 else
1293 bioq_insert_tail(&isc->bio_queue, bp);
1294 #ifdef CAM_IOSCHED_DYNAMIC
1295 if (iosched_debug > 9)
1296 printf("Qr : %p %#x\n", bp, bp->bio_cmd);
1297 if (bp->bio_cmd == BIO_READ) {
1298 isc->read_stats.in++;
1299 isc->read_stats.queued++;
1300 } else if (bp->bio_cmd == BIO_WRITE) {
1301 isc->write_stats.in++;
1302 isc->write_stats.queued++;
1303 }
1304 #endif
1305 }
1306 }
1307
1308 /*
1309 * If we have work, get it scheduled. Called with the periph lock held.
1310 */
1311 void
1312 cam_iosched_schedule(struct cam_iosched_softc *isc, struct cam_periph *periph)
1313 {
1314
1315 if (cam_iosched_has_work(isc))
1316 xpt_schedule(periph, CAM_PRIORITY_NORMAL);
1317 }
1318
1319 /*
1320 * Complete a trim request
1321 */
1322 void
1323 cam_iosched_trim_done(struct cam_iosched_softc *isc)
1324 {
1325
1326 isc->flags &= ~CAM_IOSCHED_FLAG_TRIM_ACTIVE;
1327 }
1328
1329 /*
1330 * Complete a bio. Called before we release the ccb with xpt_release_ccb so we
1331 * might use notes in the ccb for statistics.
1332 */
1333 int
1334 cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp,
1335 union ccb *done_ccb)
1336 {
1337 int retval = 0;
1338 #ifdef CAM_IOSCHED_DYNAMIC
1339 if (!do_dynamic_iosched)
1340 return retval;
1341
1342 if (iosched_debug > 10)
1343 printf("done: %p %#x\n", bp, bp->bio_cmd);
1344 if (bp->bio_cmd == BIO_WRITE) {
1345 retval = cam_iosched_limiter_iodone(&isc->write_stats, bp);
1346 isc->write_stats.out++;
1347 isc->write_stats.pending--;
1348 } else if (bp->bio_cmd == BIO_READ) {
1349 retval = cam_iosched_limiter_iodone(&isc->read_stats, bp);
1350 isc->read_stats.out++;
1351 isc->read_stats.pending--;
1352 } else if (bp->bio_cmd == BIO_DELETE) {
1353 isc->trim_stats.out++;
1354 isc->trim_stats.pending--;
1355 } else if (bp->bio_cmd != BIO_FLUSH) {
1356 if (iosched_debug)
1357 printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd);
1358 }
1359
1360 if (!(bp->bio_flags & BIO_ERROR))
1361 cam_iosched_io_metric_update(isc, done_ccb->ccb_h.qos.sim_data,
1362 bp->bio_cmd, bp->bio_bcount);
1363 #endif
1364 return retval;
1365 }
1366
1367 /*
1368 * Tell the io scheduler that you've pushed a trim down into the sim.
1369 * xxx better place for this?
1370 */
1371 void
1372 cam_iosched_submit_trim(struct cam_iosched_softc *isc)
1373 {
1374
1375 isc->flags |= CAM_IOSCHED_FLAG_TRIM_ACTIVE;
1376 }
1377
1378 /*
1379 * Change the sorting policy hint for I/O transactions for this device.
1380 */
1381 void
1382 cam_iosched_set_sort_queue(struct cam_iosched_softc *isc, int val)
1383 {
1384
1385 isc->sort_io_queue = val;
1386 }
1387
1388 int
1389 cam_iosched_has_work_flags(struct cam_iosched_softc *isc, uint32_t flags)
1390 {
1391 return isc->flags & flags;
1392 }
1393
1394 void
1395 cam_iosched_set_work_flags(struct cam_iosched_softc *isc, uint32_t flags)
1396 {
1397 isc->flags |= flags;
1398 }
1399
1400 void
1401 cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags)
1402 {
1403 isc->flags &= ~flags;
1404 }
1405
1406 #ifdef CAM_IOSCHED_DYNAMIC
1407 /*
1408 * After the method presented in Jack Crenshaw's 1998 article "Integer
1409 * Suqare Roots," reprinted at
1410 * http://www.embedded.com/electronics-blogs/programmer-s-toolbox/4219659/Integer-Square-Roots
1411 * and well worth the read. Briefly, we find the power of 4 that's the
1412 * largest smaller than val. We then check each smaller power of 4 to
1413 * see if val is still bigger. The right shifts at each step divide
1414 * the result by 2 which after successive application winds up
1415 * accumulating the right answer. It could also have been accumulated
1416 * using a separate root counter, but this code is smaller and faster
1417 * than that method. This method is also integer size invariant.
1418 * It returns floor(sqrt((float)val)), or the larget integer less than
1419 * or equal to the square root.
1420 */
1421 static uint64_t
1422 isqrt64(uint64_t val)
1423 {
1424 uint64_t res = 0;
1425 uint64_t bit = 1ULL << (sizeof(uint64_t) * NBBY - 2);
1426
1427 /*
1428 * Find the largest power of 4 smaller than val.
1429 */
1430 while (bit > val)
1431 bit >>= 2;
1432
1433 /*
1434 * Accumulate the answer, one bit at a time (we keep moving
1435 * them over since 2 is the square root of 4 and we test
1436 * powers of 4). We accumulate where we find the bit, but
1437 * the successive shifts land the bit in the right place
1438 * by the end.
1439 */
1440 while (bit != 0) {
1441 if (val >= res + bit) {
1442 val -= res + bit;
1443 res = (res >> 1) + bit;
1444 } else
1445 res >>= 1;
1446 bit >>= 2;
1447 }
1448
1449 return res;
1450 }
1451
1452 /*
1453 * a and b are 32.32 fixed point stored in a 64-bit word.
1454 * Let al and bl be the .32 part of a and b.
1455 * Let ah and bh be the 32 part of a and b.
1456 * R is the radix and is 1 << 32
1457 *
1458 * a * b
1459 * (ah + al / R) * (bh + bl / R)
1460 * ah * bh + (al * bh + ah * bl) / R + al * bl / R^2
1461 *
1462 * After multiplicaiton, we have to renormalize by multiply by
1463 * R, so we wind up with
1464 * ah * bh * R + al * bh + ah * bl + al * bl / R
1465 * which turns out to be a very nice way to compute this value
1466 * so long as ah and bh are < 65536 there's no loss of high bits
1467 * and the low order bits are below the threshold of caring for
1468 * this application.
1469 */
1470 static uint64_t
1471 mul(uint64_t a, uint64_t b)
1472 {
1473 uint64_t al, ah, bl, bh;
1474 al = a & 0xffffffff;
1475 ah = a >> 32;
1476 bl = b & 0xffffffff;
1477 bh = b >> 32;
1478 return ((ah * bh) << 32) + al * bh + ah * bl + ((al * bl) >> 32);
1479 }
1480
1481 static void
1482 cam_iosched_update(struct iop_stats *iop, sbintime_t sim_latency)
1483 {
1484 sbintime_t y, yy;
1485 uint64_t var;
1486
1487 /*
1488 * Classic expoentially decaying average with a tiny alpha
1489 * (2 ^ -alpha_bits). For more info see the NIST statistical
1490 * handbook.
1491 *
1492 * ema_t = y_t * alpha + ema_t-1 * (1 - alpha)
1493 * alpha = 1 / (1 << alpha_bits)
1494 *
1495 * Since alpha is a power of two, we can compute this w/o any mult or
1496 * division.
1497 */
1498 y = sim_latency;
1499 iop->ema = (y + (iop->ema << alpha_bits) - iop->ema) >> alpha_bits;
1500
1501 yy = mul(y, y);
1502 iop->emss = (yy + (iop->emss << alpha_bits) - iop->emss) >> alpha_bits;
1503
1504 /*
1505 * s_1 = sum of data
1506 * s_2 = sum of data * data
1507 * ema ~ mean (or s_1 / N)
1508 * emss ~ s_2 / N
1509 *
1510 * sd = sqrt((N * s_2 - s_1 ^ 2) / (N * (N - 1)))
1511 * sd = sqrt((N * s_2 / N * (N - 1)) - (s_1 ^ 2 / (N * (N - 1))))
1512 *
1513 * N ~ 2 / alpha - 1
1514 * alpha < 1 / 16 (typically much less)
1515 * N > 31 --> N large so N * (N - 1) is approx N * N
1516 *
1517 * substituting and rearranging:
1518 * sd ~ sqrt(s_2 / N - (s_1 / N) ^ 2)
1519 * ~ sqrt(emss - ema ^ 2);
1520 * which is the formula used here to get a decent estimate of sd which
1521 * we use to detect outliers. Note that when first starting up, it
1522 * takes a while for emss sum of squares estimator to converge on a
1523 * good value. during this time, it can be less than ema^2. We
1524 * compute a sd of 0 in that case, and ignore outliers.
1525 */
1526 var = iop->emss - mul(iop->ema, iop->ema);
1527 iop->sd = (int64_t)var < 0 ? 0 : isqrt64(var);
1528 }
1529
1530 #ifdef CAM_IOSCHED_DYNAMIC
1531 static void
1532 cam_iosched_io_metric_update(struct cam_iosched_softc *isc,
1533 sbintime_t sim_latency, int cmd, size_t size)
1534 {
1535 /* xxx Do we need to scale based on the size of the I/O ? */
1536 switch (cmd) {
1537 case BIO_READ:
1538 cam_iosched_update(&isc->read_stats, sim_latency);
1539 break;
1540 case BIO_WRITE:
1541 cam_iosched_update(&isc->write_stats, sim_latency);
1542 break;
1543 case BIO_DELETE:
1544 cam_iosched_update(&isc->trim_stats, sim_latency);
1545 break;
1546 default:
1547 break;
1548 }
1549 }
1550 #endif
1551
1552 #ifdef DDB
1553 static int biolen(struct bio_queue_head *bq)
1554 {
1555 int i = 0;
1556 struct bio *bp;
1557
1558 TAILQ_FOREACH(bp, &bq->queue, bio_queue) {
1559 i++;
1560 }
1561 return i;
1562 }
1563
1564 /*
1565 * Show the internal state of the I/O scheduler.
1566 */
1567 DB_SHOW_COMMAND(iosched, cam_iosched_db_show)
1568 {
1569 struct cam_iosched_softc *isc;
1570
1571 if (!have_addr) {
1572 db_printf("Need addr\n");
1573 return;
1574 }
1575 isc = (struct cam_iosched_softc *)addr;
1576 db_printf("pending_reads: %d\n", isc->read_stats.pending);
1577 db_printf("min_reads: %d\n", isc->read_stats.min);
1578 db_printf("max_reads: %d\n", isc->read_stats.max);
1579 db_printf("reads: %d\n", isc->read_stats.total);
1580 db_printf("in_reads: %d\n", isc->read_stats.in);
1581 db_printf("out_reads: %d\n", isc->read_stats.out);
1582 db_printf("queued_reads: %d\n", isc->read_stats.queued);
1583 db_printf("Current Q len %d\n", biolen(&isc->bio_queue));
1584 db_printf("pending_writes: %d\n", isc->write_stats.pending);
1585 db_printf("min_writes: %d\n", isc->write_stats.min);
1586 db_printf("max_writes: %d\n", isc->write_stats.max);
1587 db_printf("writes: %d\n", isc->write_stats.total);
1588 db_printf("in_writes: %d\n", isc->write_stats.in);
1589 db_printf("out_writes: %d\n", isc->write_stats.out);
1590 db_printf("queued_writes: %d\n", isc->write_stats.queued);
1591 db_printf("Current Q len %d\n", biolen(&isc->write_queue));
1592 db_printf("pending_trims: %d\n", isc->trim_stats.pending);
1593 db_printf("min_trims: %d\n", isc->trim_stats.min);
1594 db_printf("max_trims: %d\n", isc->trim_stats.max);
1595 db_printf("trims: %d\n", isc->trim_stats.total);
1596 db_printf("in_trims: %d\n", isc->trim_stats.in);
1597 db_printf("out_trims: %d\n", isc->trim_stats.out);
1598 db_printf("queued_trims: %d\n", isc->trim_stats.queued);
1599 db_printf("Current Q len %d\n", biolen(&isc->trim_queue));
1600 db_printf("read_bias: %d\n", isc->read_bias);
1601 db_printf("current_read_bias: %d\n", isc->current_read_bias);
1602 db_printf("Trim active? %s\n",
1603 (isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) ? "yes" : "no");
1604 }
1605 #endif
1606 #endif
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