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