2 * CAM IO Scheduler Interface
4 * SPDX-License-Identifier: BSD-2-Clause
6 * Copyright (c) 2015 Netflix, Inc.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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.
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
33 #include <sys/cdefs.h>
34 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/kernel.h>
40 #include <sys/malloc.h>
41 #include <sys/mutex.h>
43 #include <sys/sysctl.h>
46 #include <cam/cam_ccb.h>
47 #include <cam/cam_periph.h>
48 #include <cam/cam_xpt_periph.h>
49 #include <cam/cam_xpt_internal.h>
50 #include <cam/cam_iosched.h>
54 static MALLOC_DEFINE(M_CAMSCHED, "CAM I/O Scheduler",
55 "CAM I/O Scheduler buffers");
57 static SYSCTL_NODE(_kern_cam, OID_AUTO, iosched, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
58 "CAM I/O Scheduler parameters");
61 * Default I/O scheduler for FreeBSD. This implementation is just a thin-vineer
62 * over the bioq_* interface, with notions of separate calls for normal I/O and
65 * When CAM_IOSCHED_DYNAMIC is defined, the scheduler is enhanced to dynamically
66 * steer the rate of one type of traffic to help other types of traffic (eg
67 * limit writes when read latency deteriorates on SSDs).
70 #ifdef CAM_IOSCHED_DYNAMIC
72 static bool do_dynamic_iosched = true;
73 SYSCTL_BOOL(_kern_cam_iosched, OID_AUTO, dynamic, CTLFLAG_RDTUN,
74 &do_dynamic_iosched, 1,
75 "Enable Dynamic I/O scheduler optimizations.");
78 * For an EMA, with an alpha of alpha, we know
82 * where N is the number of samples that 86% of the current
83 * EMA is derived from.
85 * So we invent[*] alpha_bits:
86 * alpha_bits = -log_2(alpha)
87 * alpha = 2^-alpha_bits
89 * N = 1 + 2^(alpha_bits + 1)
91 * The default 9 gives a 1025 lookback for 86% of the data.
92 * For a brief intro: https://en.wikipedia.org/wiki/Moving_average
94 * [*] Steal from the load average code and many other places.
95 * Note: See computation of EMA and EMVAR for acceptable ranges of alpha.
97 static int alpha_bits = 9;
98 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, alpha_bits, CTLFLAG_RWTUN,
100 "Bits in EMA's alpha.");
103 * Different parameters for the buckets of latency we keep track of. These are all
104 * published read-only since at present they are compile time constants.
106 * Bucket base is the upper bounds of the first latency bucket. It's currently 20us.
107 * With 20 buckets (see below), that leads to a geometric progression with a max size
108 * of 5.2s which is safeily larger than 1s to help diagnose extreme outliers better.
111 #define BUCKET_BASE ((SBT_1S / 50000) + 1) /* 20us */
113 static sbintime_t bucket_base = BUCKET_BASE;
114 SYSCTL_SBINTIME_USEC(_kern_cam_iosched, OID_AUTO, bucket_base_us, CTLFLAG_RD,
116 "Size of the smallest latency bucket");
119 * Bucket ratio is the geometric progression for the bucket. For a bucket b_n
120 * the size of bucket b_n+1 is b_n * bucket_ratio / 100.
122 static int bucket_ratio = 200; /* Rather hard coded at the moment */
123 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, bucket_ratio, CTLFLAG_RD,
125 "Latency Bucket Ratio for geometric progression.");
128 * Number of total buckets. Starting at BUCKET_BASE, each one is a power of 2.
131 #define LAT_BUCKETS 20 /* < 20us < 40us ... < 2^(n-1)*20us >= 2^(n-1)*20us */
133 static int lat_buckets = LAT_BUCKETS;
134 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, buckets, CTLFLAG_RD,
135 &lat_buckets, LAT_BUCKETS,
136 "Total number of latency buckets published");
139 * Read bias: how many reads do we favor before scheduling a write
140 * when we have a choice.
142 static int default_read_bias = 0;
143 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, read_bias, CTLFLAG_RWTUN,
144 &default_read_bias, 0,
145 "Default read bias for new devices.");
148 struct cam_iosched_softc;
150 int iosched_debug = 0;
153 none = 0, /* No limits */
154 queue_depth, /* Limit how many ops we queue to SIM */
155 iops, /* Limit # of IOPS to the drive */
156 bandwidth, /* Limit bandwidth to the drive */
160 static const char *cam_iosched_limiter_names[] =
161 { "none", "queue_depth", "iops", "bandwidth" };
164 * Called to initialize the bits of the iop_stats structure relevant to the
165 * limiter. Called just after the limiter is set.
167 typedef int l_init_t(struct iop_stats *);
172 typedef int l_tick_t(struct iop_stats *);
175 * Called to see if the limiter thinks this IOP can be allowed to
176 * proceed. If so, the limiter assumes that the IOP proceeded
177 * and makes any accounting of it that's needed.
179 typedef int l_iop_t(struct iop_stats *, struct bio *);
182 * Called when an I/O completes so the limiter can update its
183 * accounting. Pending I/Os may complete in any order (even when
184 * sent to the hardware at the same time), so the limiter may not
185 * make any assumptions other than this I/O has completed. If it
186 * returns 1, then xpt_schedule() needs to be called again.
188 typedef int l_iodone_t(struct iop_stats *, struct bio *);
190 static l_iop_t cam_iosched_qd_iop;
191 static l_iop_t cam_iosched_qd_caniop;
192 static l_iodone_t cam_iosched_qd_iodone;
194 static l_init_t cam_iosched_iops_init;
195 static l_tick_t cam_iosched_iops_tick;
196 static l_iop_t cam_iosched_iops_caniop;
197 static l_iop_t cam_iosched_iops_iop;
199 static l_init_t cam_iosched_bw_init;
200 static l_tick_t cam_iosched_bw_tick;
201 static l_iop_t cam_iosched_bw_caniop;
202 static l_iop_t cam_iosched_bw_iop;
209 l_iodone_t *l_iodone;
221 .l_caniop = cam_iosched_qd_caniop,
222 .l_iop = cam_iosched_qd_iop,
223 .l_iodone= cam_iosched_qd_iodone,
226 .l_init = cam_iosched_iops_init,
227 .l_tick = cam_iosched_iops_tick,
228 .l_caniop = cam_iosched_iops_caniop,
229 .l_iop = cam_iosched_iops_iop,
233 .l_init = cam_iosched_bw_init,
234 .l_tick = cam_iosched_bw_tick,
235 .l_caniop = cam_iosched_bw_caniop,
236 .l_iop = cam_iosched_bw_iop,
243 * sysctl state for this subnode.
245 struct sysctl_ctx_list sysctl_ctx;
246 struct sysctl_oid *sysctl_tree;
249 * Information about the current rate limiters, if any
251 io_limiter limiter; /* How are I/Os being limited */
252 int min; /* Low range of limit */
253 int max; /* High range of limit */
254 int current; /* Current rate limiter */
255 int l_value1; /* per-limiter scratch value 1. */
256 int l_value2; /* per-limiter scratch value 2. */
259 * Debug information about counts of I/Os that have gone through the
262 int pending; /* I/Os pending in the hardware */
263 int queued; /* number currently in the queue */
264 int total; /* Total for all time -- wraps */
265 int in; /* number queued all time -- wraps */
266 int out; /* number completed all time -- wraps */
267 int errs; /* Number of I/Os completed with error -- wraps */
270 * Statistics on different bits of the process.
272 /* Exp Moving Average, see alpha_bits for more details */
275 sbintime_t sd; /* Last computed sd */
277 uint32_t state_flags;
278 #define IOP_RATE_LIMITED 1u
280 uint64_t latencies[LAT_BUCKETS];
282 struct cam_iosched_softc *softc;
286 set_max = 0, /* current = max */
287 read_latency, /* Steer read latency by throttling writes */
288 cl_max /* Keep last */
291 static const char *cam_iosched_control_type_names[] =
292 { "set_max", "read_latency" };
294 struct control_loop {
296 * sysctl state for this subnode.
298 struct sysctl_ctx_list sysctl_ctx;
299 struct sysctl_oid *sysctl_tree;
301 sbintime_t next_steer; /* Time of next steer */
302 sbintime_t steer_interval; /* How often do we steer? */
306 control_type type; /* What type of control? */
307 int last_count; /* Last I/O count */
309 struct cam_iosched_softc *softc;
314 struct cam_iosched_softc {
315 struct bio_queue_head bio_queue;
316 struct bio_queue_head trim_queue;
317 /* scheduler flags < 16, user flags >= 16 */
320 int trim_goal; /* # of trims to queue before sending */
321 int trim_ticks; /* Max ticks to hold trims */
322 int last_trim_tick; /* Last 'tick' time ld a trim */
323 int queued_trims; /* Number of trims in the queue */
324 #ifdef CAM_IOSCHED_DYNAMIC
325 int read_bias; /* Read bias setting */
326 int current_read_bias; /* Current read bias state */
328 int load; /* EMA of 'load average' of disk / 2^16 */
330 struct bio_queue_head write_queue;
331 struct iop_stats read_stats, write_stats, trim_stats;
332 struct sysctl_ctx_list sysctl_ctx;
333 struct sysctl_oid *sysctl_tree;
335 int quanta; /* Number of quanta per second */
336 struct callout ticker; /* Callout for our quota system */
337 struct cam_periph *periph; /* cam periph associated with this device */
338 uint32_t this_frac; /* Fraction of a second (1024ths) for this tick */
339 sbintime_t last_time; /* Last time we ticked */
340 struct control_loop cl;
341 sbintime_t max_lat; /* when != 0, if iop latency > max_lat, call max_lat_fcn */
342 cam_iosched_latfcn_t latfcn;
347 #ifdef CAM_IOSCHED_DYNAMIC
349 * helper functions to call the limsw functions.
352 cam_iosched_limiter_init(struct iop_stats *ios)
354 int lim = ios->limiter;
356 /* maybe this should be a kassert */
357 if (lim < none || lim >= limiter_max)
360 if (limsw[lim].l_init)
361 return limsw[lim].l_init(ios);
367 cam_iosched_limiter_tick(struct iop_stats *ios)
369 int lim = ios->limiter;
371 /* maybe this should be a kassert */
372 if (lim < none || lim >= limiter_max)
375 if (limsw[lim].l_tick)
376 return limsw[lim].l_tick(ios);
382 cam_iosched_limiter_iop(struct iop_stats *ios, struct bio *bp)
384 int lim = ios->limiter;
386 /* maybe this should be a kassert */
387 if (lim < none || lim >= limiter_max)
390 if (limsw[lim].l_iop)
391 return limsw[lim].l_iop(ios, bp);
397 cam_iosched_limiter_caniop(struct iop_stats *ios, struct bio *bp)
399 int lim = ios->limiter;
401 /* maybe this should be a kassert */
402 if (lim < none || lim >= limiter_max)
405 if (limsw[lim].l_caniop)
406 return limsw[lim].l_caniop(ios, bp);
412 cam_iosched_limiter_iodone(struct iop_stats *ios, struct bio *bp)
414 int lim = ios->limiter;
416 /* maybe this should be a kassert */
417 if (lim < none || lim >= limiter_max)
420 if (limsw[lim].l_iodone)
421 return limsw[lim].l_iodone(ios, bp);
427 * Functions to implement the different kinds of limiters
431 cam_iosched_qd_iop(struct iop_stats *ios, struct bio *bp)
434 if (ios->current <= 0 || ios->pending < ios->current)
441 cam_iosched_qd_caniop(struct iop_stats *ios, struct bio *bp)
444 if (ios->current <= 0 || ios->pending < ios->current)
451 cam_iosched_qd_iodone(struct iop_stats *ios, struct bio *bp)
454 if (ios->current <= 0 || ios->pending != ios->current)
461 cam_iosched_iops_init(struct iop_stats *ios)
464 ios->l_value1 = ios->current / ios->softc->quanta;
465 if (ios->l_value1 <= 0)
473 cam_iosched_iops_tick(struct iop_stats *ios)
478 * Allow at least one IO per tick until all
479 * the IOs for this interval have been spent.
481 new_ios = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16);
482 if (new_ios < 1 && ios->l_value2 < ios->current) {
488 * If this a new accounting interval, discard any "unspent" ios
489 * granted in the previous interval. Otherwise add the new ios to
490 * the previously granted ones that haven't been spent yet.
492 if ((ios->softc->total_ticks % ios->softc->quanta) == 0) {
493 ios->l_value1 = new_ios;
496 ios->l_value1 += new_ios;
503 cam_iosched_iops_caniop(struct iop_stats *ios, struct bio *bp)
507 * So if we have any more IOPs left, allow it,
508 * otherwise wait. If current iops is 0, treat that
509 * as unlimited as a failsafe.
511 if (ios->current > 0 && ios->l_value1 <= 0)
517 cam_iosched_iops_iop(struct iop_stats *ios, struct bio *bp)
521 rv = cam_iosched_limiter_caniop(ios, bp);
529 cam_iosched_bw_init(struct iop_stats *ios)
532 /* ios->current is in kB/s, so scale to bytes */
533 ios->l_value1 = ios->current * 1000 / ios->softc->quanta;
539 cam_iosched_bw_tick(struct iop_stats *ios)
544 * If we're in the hole for available quota from
545 * the last time, then add the quantum for this.
546 * If we have any left over from last quantum,
547 * then too bad, that's lost. Also, ios->current
548 * is in kB/s, so scale.
550 * We also allow up to 4 quanta of credits to
551 * accumulate to deal with burstiness. 4 is extremely
554 bw = (int)((ios->current * 1000ull * (uint64_t)ios->softc->this_frac) >> 16);
555 if (ios->l_value1 < bw * 4)
562 cam_iosched_bw_caniop(struct iop_stats *ios, struct bio *bp)
565 * So if we have any more bw quota left, allow it,
566 * otherwise wait. Note, we'll go negative and that's
567 * OK. We'll just get a little less next quota.
569 * Note on going negative: that allows us to process
570 * requests in order better, since we won't allow
571 * shorter reads to get around the long one that we
572 * don't have the quota to do just yet. It also prevents
573 * starvation by being a little more permissive about
574 * what we let through this quantum (to prevent the
575 * starvation), at the cost of getting a little less
578 * Also note that if the current limit is <= 0,
579 * we treat it as unlimited as a failsafe.
581 if (ios->current > 0 && ios->l_value1 <= 0)
588 cam_iosched_bw_iop(struct iop_stats *ios, struct bio *bp)
592 rv = cam_iosched_limiter_caniop(ios, bp);
594 ios->l_value1 -= bp->bio_length;
599 static void cam_iosched_cl_maybe_steer(struct control_loop *clp);
602 cam_iosched_ticker(void *arg)
604 struct cam_iosched_softc *isc = arg;
605 sbintime_t now, delta;
608 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc);
611 delta = now - isc->last_time;
612 isc->this_frac = (uint32_t)delta >> 16; /* Note: discards seconds -- should be 0 harmless if not */
613 isc->last_time = now;
615 cam_iosched_cl_maybe_steer(&isc->cl);
617 cam_iosched_limiter_tick(&isc->read_stats);
618 cam_iosched_limiter_tick(&isc->write_stats);
619 cam_iosched_limiter_tick(&isc->trim_stats);
621 cam_iosched_schedule(isc, isc->periph);
624 * isc->load is an EMA of the pending I/Os at each tick. The number of
625 * pending I/Os is the sum of the I/Os queued to the hardware, and those
626 * in the software queue that could be queued to the hardware if there
629 * ios_stats.pending is a count of requests in the SIM right now for
630 * each of these types of I/O. So the total pending count is the sum of
631 * these I/Os and the sum of the queued I/Os still in the software queue
632 * for those operations that aren't being rate limited at the moment.
634 * The reason for the rate limiting bit is because those I/Os
635 * aren't part of the software queued load (since we could
636 * give them to hardware, but choose not to).
638 * Note: due to a bug in counting pending TRIM in the device, we
639 * don't include them in this count. We count each BIO_DELETE in
640 * the pending count, but the periph drivers collapse them down
641 * into one TRIM command. That one trim command gets the completion
642 * so the counts get off.
644 pending = isc->read_stats.pending + isc->write_stats.pending /* + isc->trim_stats.pending */;
645 pending += !!(isc->read_stats.state_flags & IOP_RATE_LIMITED) * isc->read_stats.queued +
646 !!(isc->write_stats.state_flags & IOP_RATE_LIMITED) * isc->write_stats.queued /* +
647 !!(isc->trim_stats.state_flags & IOP_RATE_LIMITED) * isc->trim_stats.queued */ ;
649 pending /= isc->periph->path->device->ccbq.total_openings;
651 isc->load = (pending + (isc->load << 13) - isc->load) >> 13; /* see above: 13 -> 16139 / 200/s = ~81s ~1 minute */
657 cam_iosched_cl_init(struct control_loop *clp, struct cam_iosched_softc *isc)
660 clp->next_steer = sbinuptime();
662 clp->steer_interval = SBT_1S * 5; /* Let's start out steering every 5s */
663 clp->lolat = 5 * SBT_1MS;
664 clp->hilat = 15 * SBT_1MS;
665 clp->alpha = 20; /* Alpha == gain. 20 = .2 */
670 cam_iosched_cl_maybe_steer(struct control_loop *clp)
672 struct cam_iosched_softc *isc;
677 now = isc->last_time;
678 if (now < clp->next_steer)
681 clp->next_steer = now + clp->steer_interval;
684 if (isc->write_stats.current != isc->write_stats.max)
685 printf("Steering write from %d kBps to %d kBps\n",
686 isc->write_stats.current, isc->write_stats.max);
687 isc->read_stats.current = isc->read_stats.max;
688 isc->write_stats.current = isc->write_stats.max;
689 isc->trim_stats.current = isc->trim_stats.max;
692 old = isc->write_stats.current;
693 lat = isc->read_stats.ema;
695 * Simple PLL-like engine. Since we're steering to a range for
696 * the SP (set point) that makes things a little more
697 * complicated. In addition, we're not directly controlling our
698 * PV (process variable), the read latency, but instead are
699 * manipulating the write bandwidth limit for our MV
700 * (manipulation variable), analysis of this code gets a bit
701 * messy. Also, the MV is a very noisy control surface for read
702 * latency since it is affected by many hidden processes inside
703 * the device which change how responsive read latency will be
704 * in reaction to changes in write bandwidth. Unlike the classic
705 * boiler control PLL. this may result in over-steering while
706 * the SSD takes its time to react to the new, lower load. This
707 * is why we use a relatively low alpha of between .1 and .25 to
708 * compensate for this effect. At .1, it takes ~22 steering
709 * intervals to back off by a factor of 10. At .2 it only takes
710 * ~10. At .25 it only takes ~8. However some preliminary data
711 * from the SSD drives suggests a reasponse time in 10's of
712 * seconds before latency drops regardless of the new write
713 * rate. Careful observation will be required to tune this
716 * Also, when there's no read traffic, we jack up the write
717 * limit too regardless of the last read latency. 10 is
718 * somewhat arbitrary.
720 if (lat < clp->lolat || isc->read_stats.total - clp->last_count < 10)
721 isc->write_stats.current = isc->write_stats.current *
722 (100 + clp->alpha) / 100; /* Scale up */
723 else if (lat > clp->hilat)
724 isc->write_stats.current = isc->write_stats.current *
725 (100 - clp->alpha) / 100; /* Scale down */
726 clp->last_count = isc->read_stats.total;
729 * Even if we don't steer, per se, enforce the min/max limits as
730 * those may have changed.
732 if (isc->write_stats.current < isc->write_stats.min)
733 isc->write_stats.current = isc->write_stats.min;
734 if (isc->write_stats.current > isc->write_stats.max)
735 isc->write_stats.current = isc->write_stats.max;
736 if (old != isc->write_stats.current && iosched_debug)
737 printf("Steering write from %d kBps to %d kBps due to latency of %jdus\n",
738 old, isc->write_stats.current,
739 (uintmax_t)((uint64_t)1000000 * (uint32_t)lat) >> 32);
748 * Trim or similar currently pending completion. Should only be set for
749 * those drivers wishing only one Trim active at a time.
751 #define CAM_IOSCHED_FLAG_TRIM_ACTIVE (1ul << 0)
752 /* Callout active, and needs to be torn down */
753 #define CAM_IOSCHED_FLAG_CALLOUT_ACTIVE (1ul << 1)
755 /* Periph drivers set these flags to indicate work */
756 #define CAM_IOSCHED_FLAG_WORK_FLAGS ((0xffffu) << 16)
758 #ifdef CAM_IOSCHED_DYNAMIC
760 cam_iosched_io_metric_update(struct cam_iosched_softc *isc,
761 sbintime_t sim_latency, int cmd, size_t size);
765 cam_iosched_has_flagged_work(struct cam_iosched_softc *isc)
767 return !!(isc->flags & CAM_IOSCHED_FLAG_WORK_FLAGS);
771 cam_iosched_has_io(struct cam_iosched_softc *isc)
773 #ifdef CAM_IOSCHED_DYNAMIC
774 if (do_dynamic_iosched) {
775 struct bio *rbp = bioq_first(&isc->bio_queue);
776 struct bio *wbp = bioq_first(&isc->write_queue);
777 bool can_write = wbp != NULL &&
778 cam_iosched_limiter_caniop(&isc->write_stats, wbp) == 0;
779 bool can_read = rbp != NULL &&
780 cam_iosched_limiter_caniop(&isc->read_stats, rbp) == 0;
781 if (iosched_debug > 2) {
782 printf("can write %d: pending_writes %d max_writes %d\n", can_write, isc->write_stats.pending, isc->write_stats.max);
783 printf("can read %d: read_stats.pending %d max_reads %d\n", can_read, isc->read_stats.pending, isc->read_stats.max);
784 printf("Queued reads %d writes %d\n", isc->read_stats.queued, isc->write_stats.queued);
786 return can_read || can_write;
789 return bioq_first(&isc->bio_queue) != NULL;
793 cam_iosched_has_more_trim(struct cam_iosched_softc *isc)
797 bp = bioq_first(&isc->trim_queue);
798 #ifdef CAM_IOSCHED_DYNAMIC
799 if (do_dynamic_iosched) {
801 * If we're limiting trims, then defer action on trims
804 if (bp == NULL || cam_iosched_limiter_caniop(&isc->trim_stats, bp) != 0)
810 * If we've set a trim_goal, then if we exceed that allow trims
811 * to be passed back to the driver. If we've also set a tick timeout
812 * allow trims back to the driver. Otherwise, don't allow trims yet.
814 if (isc->trim_goal > 0) {
815 if (isc->queued_trims >= isc->trim_goal)
817 if (isc->queued_trims > 0 &&
818 isc->trim_ticks > 0 &&
819 ticks - isc->last_trim_tick > isc->trim_ticks)
824 /* NB: Should perhaps have a max trim active independent of I/O limiters */
825 return !(isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) && bp != NULL;
828 #define cam_iosched_sort_queue(isc) ((isc)->sort_io_queue >= 0 ? \
829 (isc)->sort_io_queue : cam_sort_io_queues)
832 cam_iosched_has_work(struct cam_iosched_softc *isc)
834 #ifdef CAM_IOSCHED_DYNAMIC
835 if (iosched_debug > 2)
836 printf("has work: %d %d %d\n", cam_iosched_has_io(isc),
837 cam_iosched_has_more_trim(isc),
838 cam_iosched_has_flagged_work(isc));
841 return cam_iosched_has_io(isc) ||
842 cam_iosched_has_more_trim(isc) ||
843 cam_iosched_has_flagged_work(isc);
846 #ifdef CAM_IOSCHED_DYNAMIC
848 cam_iosched_iop_stats_init(struct cam_iosched_softc *isc, struct iop_stats *ios)
853 ios->max = ios->current = 300000;
863 cam_iosched_limiter_init(ios);
867 cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS)
870 struct iop_stats *ios;
871 struct cam_iosched_softc *isc;
877 value = ios->limiter;
878 if (value < none || value >= limiter_max)
881 p = cam_iosched_limiter_names[value];
883 strlcpy(buf, p, sizeof(buf));
884 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
885 if (error != 0 || req->newptr == NULL)
888 cam_periph_lock(isc->periph);
890 for (i = none; i < limiter_max; i++) {
891 if (strcmp(buf, cam_iosched_limiter_names[i]) != 0)
894 error = cam_iosched_limiter_init(ios);
896 ios->limiter = value;
897 cam_periph_unlock(isc->periph);
900 /* Note: disk load averate requires ticker to be always running */
901 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc);
902 isc->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
904 cam_periph_unlock(isc->periph);
908 cam_periph_unlock(isc->periph);
913 cam_iosched_control_type_sysctl(SYSCTL_HANDLER_ARGS)
916 struct control_loop *clp;
917 struct cam_iosched_softc *isc;
924 if (value < none || value >= cl_max)
927 p = cam_iosched_control_type_names[value];
929 strlcpy(buf, p, sizeof(buf));
930 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
931 if (error != 0 || req->newptr == NULL)
934 for (i = set_max; i < cl_max; i++) {
935 if (strcmp(buf, cam_iosched_control_type_names[i]) != 0)
937 cam_periph_lock(isc->periph);
939 cam_periph_unlock(isc->periph);
947 cam_iosched_sbintime_sysctl(SYSCTL_HANDLER_ARGS)
954 value = *(sbintime_t *)arg1;
955 us = (uint64_t)value / SBT_1US;
956 snprintf(buf, sizeof(buf), "%ju", (intmax_t)us);
957 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
958 if (error != 0 || req->newptr == NULL)
960 us = strtoul(buf, NULL, 10);
963 *(sbintime_t *)arg1 = us * SBT_1US;
968 cam_iosched_sysctl_latencies(SYSCTL_HANDLER_ARGS)
975 sbuf_new_for_sysctl(&sb, NULL, LAT_BUCKETS * 16, req);
977 for (i = 0; i < LAT_BUCKETS - 1; i++)
978 sbuf_printf(&sb, "%jd,", (intmax_t)latencies[i]);
979 sbuf_printf(&sb, "%jd", (intmax_t)latencies[LAT_BUCKETS - 1]);
980 error = sbuf_finish(&sb);
987 cam_iosched_quanta_sysctl(SYSCTL_HANDLER_ARGS)
992 quanta = (unsigned *)arg1;
995 error = sysctl_handle_int(oidp, (int *)&value, 0, req);
996 if ((error != 0) || (req->newptr == NULL))
999 if (value < 1 || value > hz)
1008 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct iop_stats *ios, char *name)
1010 struct sysctl_oid_list *n;
1011 struct sysctl_ctx_list *ctx;
1013 ios->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx,
1014 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, name,
1015 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, name);
1016 n = SYSCTL_CHILDREN(ios->sysctl_tree);
1017 ctx = &ios->sysctl_ctx;
1019 SYSCTL_ADD_UQUAD(ctx, n,
1020 OID_AUTO, "ema", CTLFLAG_RD,
1022 "Fast Exponentially Weighted Moving Average");
1023 SYSCTL_ADD_UQUAD(ctx, n,
1024 OID_AUTO, "emvar", CTLFLAG_RD,
1026 "Fast Exponentially Weighted Moving Variance");
1028 SYSCTL_ADD_INT(ctx, n,
1029 OID_AUTO, "pending", CTLFLAG_RD,
1031 "Instantaneous # of pending transactions");
1032 SYSCTL_ADD_INT(ctx, n,
1033 OID_AUTO, "count", CTLFLAG_RD,
1035 "# of transactions submitted to hardware");
1036 SYSCTL_ADD_INT(ctx, n,
1037 OID_AUTO, "queued", CTLFLAG_RD,
1039 "# of transactions in the queue");
1040 SYSCTL_ADD_INT(ctx, n,
1041 OID_AUTO, "in", CTLFLAG_RD,
1043 "# of transactions queued to driver");
1044 SYSCTL_ADD_INT(ctx, n,
1045 OID_AUTO, "out", CTLFLAG_RD,
1047 "# of transactions completed (including with error)");
1048 SYSCTL_ADD_INT(ctx, n,
1049 OID_AUTO, "errs", CTLFLAG_RD,
1051 "# of transactions completed with an error");
1053 SYSCTL_ADD_PROC(ctx, n,
1054 OID_AUTO, "limiter",
1055 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE,
1056 ios, 0, cam_iosched_limiter_sysctl, "A",
1057 "Current limiting type.");
1058 SYSCTL_ADD_INT(ctx, n,
1059 OID_AUTO, "min", CTLFLAG_RW,
1062 SYSCTL_ADD_INT(ctx, n,
1063 OID_AUTO, "max", CTLFLAG_RW,
1066 SYSCTL_ADD_INT(ctx, n,
1067 OID_AUTO, "current", CTLFLAG_RW,
1069 "current resource");
1071 SYSCTL_ADD_PROC(ctx, n,
1072 OID_AUTO, "latencies",
1073 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
1075 cam_iosched_sysctl_latencies, "A",
1076 "Array of power of 2 latency from 1ms to 1.024s");
1080 cam_iosched_iop_stats_fini(struct iop_stats *ios)
1082 if (ios->sysctl_tree)
1083 if (sysctl_ctx_free(&ios->sysctl_ctx) != 0)
1084 printf("can't remove iosched sysctl stats context\n");
1088 cam_iosched_cl_sysctl_init(struct cam_iosched_softc *isc)
1090 struct sysctl_oid_list *n;
1091 struct sysctl_ctx_list *ctx;
1092 struct control_loop *clp;
1095 clp->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx,
1096 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, "control",
1097 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "Control loop info");
1098 n = SYSCTL_CHILDREN(clp->sysctl_tree);
1099 ctx = &clp->sysctl_ctx;
1101 SYSCTL_ADD_PROC(ctx, n,
1103 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE,
1104 clp, 0, cam_iosched_control_type_sysctl, "A",
1105 "Control loop algorithm");
1106 SYSCTL_ADD_PROC(ctx, n,
1107 OID_AUTO, "steer_interval",
1108 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE,
1109 &clp->steer_interval, 0, cam_iosched_sbintime_sysctl, "A",
1110 "How often to steer (in us)");
1111 SYSCTL_ADD_PROC(ctx, n,
1113 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE,
1114 &clp->lolat, 0, cam_iosched_sbintime_sysctl, "A",
1115 "Low water mark for Latency (in us)");
1116 SYSCTL_ADD_PROC(ctx, n,
1118 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE,
1119 &clp->hilat, 0, cam_iosched_sbintime_sysctl, "A",
1120 "Hi water mark for Latency (in us)");
1121 SYSCTL_ADD_INT(ctx, n,
1122 OID_AUTO, "alpha", CTLFLAG_RW,
1124 "Alpha for PLL (x100) aka gain");
1128 cam_iosched_cl_sysctl_fini(struct control_loop *clp)
1130 if (clp->sysctl_tree)
1131 if (sysctl_ctx_free(&clp->sysctl_ctx) != 0)
1132 printf("can't remove iosched sysctl control loop context\n");
1137 * Allocate the iosched structure. This also insulates callers from knowing
1138 * sizeof struct cam_iosched_softc.
1141 cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph)
1144 *iscp = malloc(sizeof(**iscp), M_CAMSCHED, M_NOWAIT | M_ZERO);
1147 #ifdef CAM_IOSCHED_DYNAMIC
1149 printf("CAM IOSCHEDULER Allocating entry at %p\n", *iscp);
1151 (*iscp)->sort_io_queue = -1;
1152 bioq_init(&(*iscp)->bio_queue);
1153 bioq_init(&(*iscp)->trim_queue);
1154 #ifdef CAM_IOSCHED_DYNAMIC
1155 if (do_dynamic_iosched) {
1156 bioq_init(&(*iscp)->write_queue);
1157 (*iscp)->read_bias = default_read_bias;
1158 (*iscp)->current_read_bias = 0;
1159 (*iscp)->quanta = min(hz, 200);
1160 cam_iosched_iop_stats_init(*iscp, &(*iscp)->read_stats);
1161 cam_iosched_iop_stats_init(*iscp, &(*iscp)->write_stats);
1162 cam_iosched_iop_stats_init(*iscp, &(*iscp)->trim_stats);
1163 (*iscp)->trim_stats.max = 1; /* Trims are special: one at a time for now */
1164 (*iscp)->last_time = sbinuptime();
1165 callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0);
1166 (*iscp)->periph = periph;
1167 cam_iosched_cl_init(&(*iscp)->cl, *iscp);
1168 callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta, cam_iosched_ticker, *iscp);
1169 (*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
1177 * Reclaim all used resources. This assumes that other folks have
1178 * drained the requests in the hardware. Maybe an unwise assumption.
1181 cam_iosched_fini(struct cam_iosched_softc *isc)
1184 cam_iosched_flush(isc, NULL, ENXIO);
1185 #ifdef CAM_IOSCHED_DYNAMIC
1186 cam_iosched_iop_stats_fini(&isc->read_stats);
1187 cam_iosched_iop_stats_fini(&isc->write_stats);
1188 cam_iosched_iop_stats_fini(&isc->trim_stats);
1189 cam_iosched_cl_sysctl_fini(&isc->cl);
1190 if (isc->sysctl_tree)
1191 if (sysctl_ctx_free(&isc->sysctl_ctx) != 0)
1192 printf("can't remove iosched sysctl stats context\n");
1193 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) {
1194 callout_drain(&isc->ticker);
1195 isc->flags &= ~ CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
1198 free(isc, M_CAMSCHED);
1203 * After we're sure we're attaching a device, go ahead and add
1204 * hooks for any sysctl we may wish to honor.
1206 void cam_iosched_sysctl_init(struct cam_iosched_softc *isc,
1207 struct sysctl_ctx_list *ctx, struct sysctl_oid *node)
1209 struct sysctl_oid_list *n;
1211 n = SYSCTL_CHILDREN(node);
1212 SYSCTL_ADD_INT(ctx, n,
1213 OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE,
1214 &isc->sort_io_queue, 0,
1215 "Sort IO queue to try and optimise disk access patterns");
1216 SYSCTL_ADD_INT(ctx, n,
1217 OID_AUTO, "trim_goal", CTLFLAG_RW,
1219 "Number of trims to try to accumulate before sending to hardware");
1220 SYSCTL_ADD_INT(ctx, n,
1221 OID_AUTO, "trim_ticks", CTLFLAG_RW,
1223 "IO Schedul qaunta to hold back trims for when accumulating");
1225 #ifdef CAM_IOSCHED_DYNAMIC
1226 if (!do_dynamic_iosched)
1229 isc->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx,
1230 SYSCTL_CHILDREN(node), OID_AUTO, "iosched",
1231 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "I/O scheduler statistics");
1232 n = SYSCTL_CHILDREN(isc->sysctl_tree);
1233 ctx = &isc->sysctl_ctx;
1235 cam_iosched_iop_stats_sysctl_init(isc, &isc->read_stats, "read");
1236 cam_iosched_iop_stats_sysctl_init(isc, &isc->write_stats, "write");
1237 cam_iosched_iop_stats_sysctl_init(isc, &isc->trim_stats, "trim");
1238 cam_iosched_cl_sysctl_init(isc);
1240 SYSCTL_ADD_INT(ctx, n,
1241 OID_AUTO, "read_bias", CTLFLAG_RW,
1242 &isc->read_bias, default_read_bias,
1243 "How biased towards read should we be independent of limits");
1245 SYSCTL_ADD_PROC(ctx, n,
1246 OID_AUTO, "quanta", CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE,
1247 &isc->quanta, 0, cam_iosched_quanta_sysctl, "I",
1248 "How many quanta per second do we slice the I/O up into");
1250 SYSCTL_ADD_INT(ctx, n,
1251 OID_AUTO, "total_ticks", CTLFLAG_RD,
1252 &isc->total_ticks, 0,
1253 "Total number of ticks we've done");
1255 SYSCTL_ADD_INT(ctx, n,
1256 OID_AUTO, "load", CTLFLAG_RD,
1258 "scaled load average / 100");
1260 SYSCTL_ADD_U64(ctx, n,
1261 OID_AUTO, "latency_trigger", CTLFLAG_RW,
1263 "Latency treshold to trigger callbacks");
1268 cam_iosched_set_latfcn(struct cam_iosched_softc *isc,
1269 cam_iosched_latfcn_t fnp, void *argp)
1271 #ifdef CAM_IOSCHED_DYNAMIC
1278 * Client drivers can set two parameters. "goal" is the number of BIO_DELETEs
1279 * that will be queued up before iosched will "release" the trims to the client
1280 * driver to wo with what they will (usually combine as many as possible). If we
1281 * don't get this many, after trim_ticks we'll submit the I/O anyway with
1282 * whatever we have. We do need an I/O of some kind of to clock the deferred
1283 * trims out to disk. Since we will eventually get a write for the super block
1284 * or something before we shutdown, the trims will complete. To be safe, when a
1285 * BIO_FLUSH is presented to the iosched work queue, we set the ticks time far
1286 * enough in the past so we'll present the BIO_DELETEs to the client driver.
1287 * There might be a race if no BIO_DELETESs were queued, a BIO_FLUSH comes in
1288 * and then a BIO_DELETE is sent down. No know client does this, and there's
1289 * already a race between an ordered BIO_FLUSH and any BIO_DELETEs in flight,
1290 * but no client depends on the ordering being honored.
1292 * XXX I'm not sure what the interaction between UFS direct BIOs and the BUF
1293 * flushing on shutdown. I think there's bufs that would be dependent on the BIO
1294 * finishing to write out at least metadata, so we'll be fine. To be safe, keep
1295 * the number of ticks low (less than maybe 10s) to avoid shutdown races.
1299 cam_iosched_set_trim_goal(struct cam_iosched_softc *isc, int goal)
1302 isc->trim_goal = goal;
1306 cam_iosched_set_trim_ticks(struct cam_iosched_softc *isc, int trim_ticks)
1309 isc->trim_ticks = trim_ticks;
1313 * Flush outstanding I/O. Consumers of this library don't know all the
1314 * queues we may keep, so this allows all I/O to be flushed in one
1318 cam_iosched_flush(struct cam_iosched_softc *isc, struct devstat *stp, int err)
1320 bioq_flush(&isc->bio_queue, stp, err);
1321 bioq_flush(&isc->trim_queue, stp, err);
1322 #ifdef CAM_IOSCHED_DYNAMIC
1323 if (do_dynamic_iosched)
1324 bioq_flush(&isc->write_queue, stp, err);
1328 #ifdef CAM_IOSCHED_DYNAMIC
1330 cam_iosched_get_write(struct cam_iosched_softc *isc)
1335 * We control the write rate by controlling how many requests we send
1336 * down to the drive at any one time. Fewer requests limits the
1337 * effects of both starvation when the requests take a while and write
1338 * amplification when each request is causing more than one write to
1339 * the NAND media. Limiting the queue depth like this will also limit
1340 * the write throughput and give and reads that want to compete to
1343 bp = bioq_first(&isc->write_queue);
1345 if (iosched_debug > 3)
1346 printf("No writes present in write_queue\n");
1351 * If pending read, prefer that based on current read bias
1354 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) {
1357 "Reads present and current_read_bias is %d queued "
1358 "writes %d queued reads %d\n",
1359 isc->current_read_bias, isc->write_stats.queued,
1360 isc->read_stats.queued);
1361 isc->current_read_bias--;
1362 /* We're not limiting writes, per se, just doing reads first */
1367 * See if our current limiter allows this I/O.
1369 if (cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) {
1371 printf("Can't write because limiter says no.\n");
1372 isc->write_stats.state_flags |= IOP_RATE_LIMITED;
1377 * Let's do this: We've passed all the gates and we're a go
1378 * to schedule the I/O in the SIM.
1380 isc->current_read_bias = isc->read_bias;
1381 bioq_remove(&isc->write_queue, bp);
1382 if (bp->bio_cmd == BIO_WRITE) {
1383 isc->write_stats.queued--;
1384 isc->write_stats.total++;
1385 isc->write_stats.pending++;
1387 if (iosched_debug > 9)
1388 printf("HWQ : %p %#x\n", bp, bp->bio_cmd);
1389 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED;
1395 * Put back a trim that you weren't able to actually schedule this time.
1398 cam_iosched_put_back_trim(struct cam_iosched_softc *isc, struct bio *bp)
1400 bioq_insert_head(&isc->trim_queue, bp);
1401 if (isc->queued_trims == 0)
1402 isc->last_trim_tick = ticks;
1403 isc->queued_trims++;
1404 #ifdef CAM_IOSCHED_DYNAMIC
1405 isc->trim_stats.queued++;
1406 isc->trim_stats.total--; /* since we put it back, don't double count */
1407 isc->trim_stats.pending--;
1412 * gets the next trim from the trim queue.
1414 * Assumes we're called with the periph lock held. It removes this
1415 * trim from the queue and the device must explicitly reinsert it
1416 * should the need arise.
1419 cam_iosched_next_trim(struct cam_iosched_softc *isc)
1423 bp = bioq_first(&isc->trim_queue);
1426 bioq_remove(&isc->trim_queue, bp);
1427 isc->queued_trims--;
1428 isc->last_trim_tick = ticks; /* Reset the tick timer when we take trims */
1429 #ifdef CAM_IOSCHED_DYNAMIC
1430 isc->trim_stats.queued--;
1431 isc->trim_stats.total++;
1432 isc->trim_stats.pending++;
1438 * gets an available trim from the trim queue, if there's no trim
1439 * already pending. It removes this trim from the queue and the device
1440 * must explicitly reinsert it should the need arise.
1442 * Assumes we're called with the periph lock held.
1445 cam_iosched_get_trim(struct cam_iosched_softc *isc)
1447 #ifdef CAM_IOSCHED_DYNAMIC
1451 if (!cam_iosched_has_more_trim(isc))
1453 #ifdef CAM_IOSCHED_DYNAMIC
1454 bp = bioq_first(&isc->trim_queue);
1459 * If pending read, prefer that based on current read bias setting. The
1460 * read bias is shared for both writes and TRIMs, but on TRIMs the bias
1461 * is for a combined TRIM not a single TRIM request that's come in.
1463 if (do_dynamic_iosched) {
1464 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) {
1466 printf("Reads present and current_read_bias is %d"
1467 " queued trims %d queued reads %d\n",
1468 isc->current_read_bias, isc->trim_stats.queued,
1469 isc->read_stats.queued);
1470 isc->current_read_bias--;
1471 /* We're not limiting TRIMS, per se, just doing reads first */
1475 * We're going to do a trim, so reset the bias.
1477 isc->current_read_bias = isc->read_bias;
1481 * See if our current limiter allows this I/O. Because we only call this
1482 * here, and not in next_trim, the 'bandwidth' limits for trims won't
1483 * work, while the iops or max queued limits will work. It's tricky
1484 * because we want the limits to be from the perspective of the
1485 * "commands sent to the device." To make iops work, we need to check
1486 * only here (since we want all the ops we combine to count as one). To
1487 * make bw limits work, we'd need to check in next_trim, but that would
1488 * have the effect of limiting the iops as seen from the upper layers.
1490 if (cam_iosched_limiter_iop(&isc->trim_stats, bp) != 0) {
1492 printf("Can't trim because limiter says no.\n");
1493 isc->trim_stats.state_flags |= IOP_RATE_LIMITED;
1496 isc->current_read_bias = isc->read_bias;
1497 isc->trim_stats.state_flags &= ~IOP_RATE_LIMITED;
1498 /* cam_iosched_next_trim below keeps proper book */
1500 return cam_iosched_next_trim(isc);
1504 #ifdef CAM_IOSCHED_DYNAMIC
1506 bio_next(struct bio *bp)
1508 bp = TAILQ_NEXT(bp, bio_queue);
1510 * After the first commands, the ordered bit terminates
1511 * our search because BIO_ORDERED acts like a barrier.
1513 if (bp == NULL || bp->bio_flags & BIO_ORDERED)
1519 cam_iosched_rate_limited(struct iop_stats *ios)
1521 return ios->state_flags & IOP_RATE_LIMITED;
1526 * Determine what the next bit of work to do is for the periph. The
1527 * default implementation looks to see if we have trims to do, but no
1528 * trims outstanding. If so, we do that. Otherwise we see if we have
1529 * other work. If we do, then we do that. Otherwise why were we called?
1532 cam_iosched_next_bio(struct cam_iosched_softc *isc)
1537 * See if we have a trim that can be scheduled. We can only send one
1538 * at a time down, so this takes that into account.
1540 * XXX newer TRIM commands are queueable. Revisit this when we
1543 if ((bp = cam_iosched_get_trim(isc)) != NULL)
1546 #ifdef CAM_IOSCHED_DYNAMIC
1548 * See if we have any pending writes, room in the queue for them,
1549 * and no pending reads (unless we've scheduled too many).
1550 * if so, those are next.
1552 if (do_dynamic_iosched) {
1553 if ((bp = cam_iosched_get_write(isc)) != NULL)
1558 * next, see if there's other, normal I/O waiting. If so return that.
1560 #ifdef CAM_IOSCHED_DYNAMIC
1561 if (do_dynamic_iosched) {
1562 for (bp = bioq_first(&isc->bio_queue); bp != NULL;
1563 bp = bio_next(bp)) {
1565 * For the dynamic scheduler with a read bias, bio_queue
1566 * is only for reads. However, without one, all
1567 * operations are queued. Enforce limits here for any
1568 * operation we find here.
1570 if (bp->bio_cmd == BIO_READ) {
1571 if (cam_iosched_rate_limited(&isc->read_stats) ||
1572 cam_iosched_limiter_iop(&isc->read_stats, bp) != 0) {
1573 isc->read_stats.state_flags |= IOP_RATE_LIMITED;
1576 isc->read_stats.state_flags &= ~IOP_RATE_LIMITED;
1579 * There can only be write requests on the queue when
1580 * the read bias is 0, but we need to process them
1581 * here. We do not assert for read bias == 0, however,
1582 * since it is dynamic and we can have WRITE operations
1583 * in the queue after we transition from 0 to non-zero.
1585 if (bp->bio_cmd == BIO_WRITE) {
1586 if (cam_iosched_rate_limited(&isc->write_stats) ||
1587 cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) {
1588 isc->write_stats.state_flags |= IOP_RATE_LIMITED;
1591 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED;
1594 * here we know we have a bp that's != NULL, that's not rate limited
1595 * and can be the next I/O.
1601 bp = bioq_first(&isc->bio_queue);
1605 bioq_remove(&isc->bio_queue, bp);
1606 #ifdef CAM_IOSCHED_DYNAMIC
1607 if (do_dynamic_iosched) {
1608 if (bp->bio_cmd == BIO_READ) {
1609 isc->read_stats.queued--;
1610 isc->read_stats.total++;
1611 isc->read_stats.pending++;
1612 } else if (bp->bio_cmd == BIO_WRITE) {
1613 isc->write_stats.queued--;
1614 isc->write_stats.total++;
1615 isc->write_stats.pending++;
1618 if (iosched_debug > 9)
1619 printf("HWQ : %p %#x\n", bp, bp->bio_cmd);
1625 * Driver has been given some work to do by the block layer. Tell the
1626 * scheduler about it and have it queue the work up. The scheduler module
1627 * will then return the currently most useful bit of work later, possibly
1628 * deferring work for various reasons.
1631 cam_iosched_queue_work(struct cam_iosched_softc *isc, struct bio *bp)
1635 * A BIO_SPEEDUP from the upper layers means that they have a block
1636 * shortage. At the present, this is only sent when we're trying to
1637 * allocate blocks, but have a shortage before giving up. bio_length is
1638 * the size of their shortage. We will complete just enough BIO_DELETEs
1639 * in the queue to satisfy the need. If bio_length is 0, we'll complete
1640 * them all. This allows the scheduler to delay BIO_DELETEs to improve
1641 * read/write performance without worrying about the upper layers. When
1642 * it's possibly a problem, we respond by pretending the BIO_DELETEs
1643 * just worked. We can't do anything about the BIO_DELETEs in the
1644 * hardware, though. We have to wait for them to complete.
1646 if (bp->bio_cmd == BIO_SPEEDUP) {
1651 while (bioq_first(&isc->trim_queue) &&
1652 (bp->bio_length == 0 || len < bp->bio_length)) {
1653 nbp = bioq_takefirst(&isc->trim_queue);
1654 len += nbp->bio_length;
1658 if (bp->bio_length > 0) {
1659 if (bp->bio_length > len)
1660 bp->bio_resid = bp->bio_length - len;
1670 * If we get a BIO_FLUSH, and we're doing delayed BIO_DELETEs then we
1671 * set the last tick time to one less than the current ticks minus the
1672 * delay to force the BIO_DELETEs to be presented to the client driver.
1674 if (bp->bio_cmd == BIO_FLUSH && isc->trim_ticks > 0)
1675 isc->last_trim_tick = ticks - isc->trim_ticks - 1;
1678 * Put all trims on the trim queue. Otherwise put the work on the bio
1681 if (bp->bio_cmd == BIO_DELETE) {
1682 bioq_insert_tail(&isc->trim_queue, bp);
1683 if (isc->queued_trims == 0)
1684 isc->last_trim_tick = ticks;
1685 isc->queued_trims++;
1686 #ifdef CAM_IOSCHED_DYNAMIC
1687 isc->trim_stats.in++;
1688 isc->trim_stats.queued++;
1691 #ifdef CAM_IOSCHED_DYNAMIC
1692 else if (do_dynamic_iosched && isc->read_bias != 0 &&
1693 (bp->bio_cmd != BIO_READ)) {
1694 if (cam_iosched_sort_queue(isc))
1695 bioq_disksort(&isc->write_queue, bp);
1697 bioq_insert_tail(&isc->write_queue, bp);
1698 if (iosched_debug > 9)
1699 printf("Qw : %p %#x\n", bp, bp->bio_cmd);
1700 if (bp->bio_cmd == BIO_WRITE) {
1701 isc->write_stats.in++;
1702 isc->write_stats.queued++;
1707 if (cam_iosched_sort_queue(isc))
1708 bioq_disksort(&isc->bio_queue, bp);
1710 bioq_insert_tail(&isc->bio_queue, bp);
1711 #ifdef CAM_IOSCHED_DYNAMIC
1712 if (iosched_debug > 9)
1713 printf("Qr : %p %#x\n", bp, bp->bio_cmd);
1714 if (bp->bio_cmd == BIO_READ) {
1715 isc->read_stats.in++;
1716 isc->read_stats.queued++;
1717 } else if (bp->bio_cmd == BIO_WRITE) {
1718 isc->write_stats.in++;
1719 isc->write_stats.queued++;
1726 * If we have work, get it scheduled. Called with the periph lock held.
1729 cam_iosched_schedule(struct cam_iosched_softc *isc, struct cam_periph *periph)
1732 if (cam_iosched_has_work(isc))
1733 xpt_schedule(periph, CAM_PRIORITY_NORMAL);
1737 * Complete a trim request. Mark that we no longer have one in flight.
1740 cam_iosched_trim_done(struct cam_iosched_softc *isc)
1743 isc->flags &= ~CAM_IOSCHED_FLAG_TRIM_ACTIVE;
1747 * Complete a bio. Called before we release the ccb with xpt_release_ccb so we
1748 * might use notes in the ccb for statistics.
1751 cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp,
1752 union ccb *done_ccb)
1755 #ifdef CAM_IOSCHED_DYNAMIC
1756 if (!do_dynamic_iosched)
1759 if (iosched_debug > 10)
1760 printf("done: %p %#x\n", bp, bp->bio_cmd);
1761 if (bp->bio_cmd == BIO_WRITE) {
1762 retval = cam_iosched_limiter_iodone(&isc->write_stats, bp);
1763 if ((bp->bio_flags & BIO_ERROR) != 0)
1764 isc->write_stats.errs++;
1765 isc->write_stats.out++;
1766 isc->write_stats.pending--;
1767 } else if (bp->bio_cmd == BIO_READ) {
1768 retval = cam_iosched_limiter_iodone(&isc->read_stats, bp);
1769 if ((bp->bio_flags & BIO_ERROR) != 0)
1770 isc->read_stats.errs++;
1771 isc->read_stats.out++;
1772 isc->read_stats.pending--;
1773 } else if (bp->bio_cmd == BIO_DELETE) {
1774 if ((bp->bio_flags & BIO_ERROR) != 0)
1775 isc->trim_stats.errs++;
1776 isc->trim_stats.out++;
1777 isc->trim_stats.pending--;
1778 } else if (bp->bio_cmd != BIO_FLUSH) {
1780 printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd);
1783 if ((bp->bio_flags & BIO_ERROR) == 0 && done_ccb != NULL &&
1784 (done_ccb->ccb_h.status & CAM_QOS_VALID) != 0) {
1785 sbintime_t sim_latency;
1787 sim_latency = cam_iosched_sbintime_t(done_ccb->ccb_h.qos.periph_data);
1789 cam_iosched_io_metric_update(isc, sim_latency,
1790 bp->bio_cmd, bp->bio_bcount);
1792 * Debugging code: allow callbacks to the periph driver when latency max
1793 * is exceeded. This can be useful for triggering external debugging actions.
1795 if (isc->latfcn && isc->max_lat != 0 && sim_latency > isc->max_lat)
1796 isc->latfcn(isc->latarg, sim_latency, bp);
1804 * Tell the io scheduler that you've pushed a trim down into the sim.
1805 * This also tells the I/O scheduler not to push any more trims down, so
1806 * some periphs do not call it if they can cope with multiple trims in flight.
1809 cam_iosched_submit_trim(struct cam_iosched_softc *isc)
1812 isc->flags |= CAM_IOSCHED_FLAG_TRIM_ACTIVE;
1816 * Change the sorting policy hint for I/O transactions for this device.
1819 cam_iosched_set_sort_queue(struct cam_iosched_softc *isc, int val)
1822 isc->sort_io_queue = val;
1826 cam_iosched_has_work_flags(struct cam_iosched_softc *isc, uint32_t flags)
1828 return isc->flags & flags;
1832 cam_iosched_set_work_flags(struct cam_iosched_softc *isc, uint32_t flags)
1834 isc->flags |= flags;
1838 cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags)
1840 isc->flags &= ~flags;
1843 #ifdef CAM_IOSCHED_DYNAMIC
1845 * After the method presented in Jack Crenshaw's 1998 article "Integer
1846 * Square Roots," reprinted at
1847 * http://www.embedded.com/electronics-blogs/programmer-s-toolbox/4219659/Integer-Square-Roots
1848 * and well worth the read. Briefly, we find the power of 4 that's the
1849 * largest smaller than val. We then check each smaller power of 4 to
1850 * see if val is still bigger. The right shifts at each step divide
1851 * the result by 2 which after successive application winds up
1852 * accumulating the right answer. It could also have been accumulated
1853 * using a separate root counter, but this code is smaller and faster
1854 * than that method. This method is also integer size invariant.
1855 * It returns floor(sqrt((float)val)), or the largest integer less than
1856 * or equal to the square root.
1859 isqrt64(uint64_t val)
1862 uint64_t bit = 1ULL << (sizeof(uint64_t) * NBBY - 2);
1865 * Find the largest power of 4 smaller than val.
1871 * Accumulate the answer, one bit at a time (we keep moving
1872 * them over since 2 is the square root of 4 and we test
1873 * powers of 4). We accumulate where we find the bit, but
1874 * the successive shifts land the bit in the right place
1878 if (val >= res + bit) {
1880 res = (res >> 1) + bit;
1889 static sbintime_t latencies[LAT_BUCKETS - 1] = {
1890 BUCKET_BASE << 0, /* 20us */
1908 BUCKET_BASE << 18 /* 5,242,880us */
1912 cam_iosched_update(struct iop_stats *iop, sbintime_t sim_latency)
1914 sbintime_t y, deltasq, delta;
1918 * Keep counts for latency. We do it by power of two buckets.
1919 * This helps us spot outlier behavior obscured by averages.
1921 for (i = 0; i < LAT_BUCKETS - 1; i++) {
1922 if (sim_latency < latencies[i]) {
1923 iop->latencies[i]++;
1927 if (i == LAT_BUCKETS - 1)
1928 iop->latencies[i]++; /* Put all > 8192ms values into the last bucket. */
1931 * Classic exponentially decaying average with a tiny alpha
1932 * (2 ^ -alpha_bits). For more info see the NIST statistical
1935 * ema_t = y_t * alpha + ema_t-1 * (1 - alpha) [nist]
1936 * ema_t = y_t * alpha + ema_t-1 - alpha * ema_t-1
1937 * ema_t = alpha * y_t - alpha * ema_t-1 + ema_t-1
1938 * alpha = 1 / (1 << alpha_bits)
1939 * sub e == ema_t-1, b == 1/alpha (== 1 << alpha_bits), d == y_t - ema_t-1
1940 * = y_t/b - e/b + be/b
1941 * = (y_t - e + be) / b
1944 * Since alpha is a power of two, we can compute this w/o any mult or
1947 * Variance can also be computed. Usually, it would be expressed as follows:
1948 * diff_t = y_t - ema_t-1
1949 * emvar_t = (1 - alpha) * (emavar_t-1 + diff_t^2 * alpha)
1950 * = emavar_t-1 - alpha * emavar_t-1 + delta_t^2 * alpha - (delta_t * alpha)^2
1951 * sub b == 1/alpha (== 1 << alpha_bits), e == emavar_t-1, d = delta_t^2
1952 * = e - e/b + dd/b + dd/bb
1953 * = (bbe - be + bdd + dd) / bb
1954 * = (bbe + b(dd-e) + dd) / bb (which is expanded below bb = 1<<(2*alpha_bits))
1957 * XXX possible numeric issues
1958 * o We assume right shifted integers do the right thing, since that's
1959 * implementation defined. You can change the right shifts to / (1LL << alpha).
1960 * o alpha_bits = 9 gives ema ceiling of 23 bits of seconds for ema and 14 bits
1961 * for emvar. This puts a ceiling of 13 bits on alpha since we need a
1962 * few tens of seconds of representation.
1963 * o We mitigate alpha issues by never setting it too high.
1966 delta = (y - iop->ema); /* d */
1967 iop->ema = ((iop->ema << alpha_bits) + delta) >> alpha_bits;
1970 * Were we to naively plow ahead at this point, we wind up with many numerical
1971 * issues making any SD > ~3ms unreliable. So, we shift right by 12. This leaves
1972 * us with microsecond level precision in the input, so the same in the
1973 * output. It means we can't overflow deltasq unless delta > 4k seconds. It
1974 * also means that emvar can be up 46 bits 40 of which are fraction, which
1975 * gives us a way to measure up to ~8s in the SD before the computation goes
1976 * unstable. Even the worst hard disk rarely has > 1s service time in the
1977 * drive. It does mean we have to shift left 12 bits after taking the
1978 * square root to compute the actual standard deviation estimate. This loss of
1979 * precision is preferable to needing int128 types to work. The above numbers
1980 * assume alpha=9. 10 or 11 are ok, but we start to run into issues at 12,
1981 * so 12 or 13 is OK for EMA, EMVAR and SD will be wrong in those cases.
1984 deltasq = delta * delta; /* dd */
1985 iop->emvar = ((iop->emvar << (2 * alpha_bits)) + /* bbe */
1986 ((deltasq - iop->emvar) << alpha_bits) + /* b(dd-e) */
1988 >> (2 * alpha_bits); /* div bb */
1989 iop->sd = (sbintime_t)isqrt64((uint64_t)iop->emvar) << 12;
1993 cam_iosched_io_metric_update(struct cam_iosched_softc *isc,
1994 sbintime_t sim_latency, int cmd, size_t size)
1996 /* xxx Do we need to scale based on the size of the I/O ? */
1999 cam_iosched_update(&isc->read_stats, sim_latency);
2002 cam_iosched_update(&isc->write_stats, sim_latency);
2005 cam_iosched_update(&isc->trim_stats, sim_latency);
2013 static int biolen(struct bio_queue_head *bq)
2018 TAILQ_FOREACH(bp, &bq->queue, bio_queue) {
2025 * Show the internal state of the I/O scheduler.
2027 DB_SHOW_COMMAND(iosched, cam_iosched_db_show)
2029 struct cam_iosched_softc *isc;
2032 db_printf("Need addr\n");
2035 isc = (struct cam_iosched_softc *)addr;
2036 db_printf("pending_reads: %d\n", isc->read_stats.pending);
2037 db_printf("min_reads: %d\n", isc->read_stats.min);
2038 db_printf("max_reads: %d\n", isc->read_stats.max);
2039 db_printf("reads: %d\n", isc->read_stats.total);
2040 db_printf("in_reads: %d\n", isc->read_stats.in);
2041 db_printf("out_reads: %d\n", isc->read_stats.out);
2042 db_printf("queued_reads: %d\n", isc->read_stats.queued);
2043 db_printf("Read Q len %d\n", biolen(&isc->bio_queue));
2044 db_printf("pending_writes: %d\n", isc->write_stats.pending);
2045 db_printf("min_writes: %d\n", isc->write_stats.min);
2046 db_printf("max_writes: %d\n", isc->write_stats.max);
2047 db_printf("writes: %d\n", isc->write_stats.total);
2048 db_printf("in_writes: %d\n", isc->write_stats.in);
2049 db_printf("out_writes: %d\n", isc->write_stats.out);
2050 db_printf("queued_writes: %d\n", isc->write_stats.queued);
2051 db_printf("Write Q len %d\n", biolen(&isc->write_queue));
2052 db_printf("pending_trims: %d\n", isc->trim_stats.pending);
2053 db_printf("min_trims: %d\n", isc->trim_stats.min);
2054 db_printf("max_trims: %d\n", isc->trim_stats.max);
2055 db_printf("trims: %d\n", isc->trim_stats.total);
2056 db_printf("in_trims: %d\n", isc->trim_stats.in);
2057 db_printf("out_trims: %d\n", isc->trim_stats.out);
2058 db_printf("queued_trims: %d\n", isc->trim_stats.queued);
2059 db_printf("Trim Q len %d\n", biolen(&isc->trim_queue));
2060 db_printf("read_bias: %d\n", isc->read_bias);
2061 db_printf("current_read_bias: %d\n", isc->current_read_bias);
2062 db_printf("Trim active? %s\n",
2063 (isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) ? "yes" : "no");