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 * $FreeBSD$ 30 */ 31 32 #include "opt_cam.h" 33 #include "opt_ddb.h" 34 35 #include <sys/cdefs.h> 36 __FBSDID("$FreeBSD$"); 37 38 #include <sys/param.h> 39 40 #include <sys/systm.h> 41 #include <sys/kernel.h> 42 #include <sys/bio.h> 43 #include <sys/lock.h> 44 #include <sys/malloc.h> 45 #include <sys/mutex.h> 46 #include <sys/sbuf.h> 47 #include <sys/sysctl.h> 48 49 #include <cam/cam.h> 50 #include <cam/cam_ccb.h> 51 #include <cam/cam_periph.h> 52 #include <cam/cam_xpt_periph.h> 53 #include <cam/cam_xpt_internal.h> 54 #include <cam/cam_iosched.h> 55 56 #include <ddb/ddb.h> 57 58 static MALLOC_DEFINE(M_CAMSCHED, "CAM I/O Scheduler", 59 "CAM I/O Scheduler buffers"); 60 61 static SYSCTL_NODE(_kern_cam, OID_AUTO, iosched, CTLFLAG_RD | CTLFLAG_MPSAFE, 0, 62 "CAM I/O Scheduler parameters"); 63 64 /* 65 * Default I/O scheduler for FreeBSD. This implementation is just a thin-vineer 66 * over the bioq_* interface, with notions of separate calls for normal I/O and 67 * for trims. 68 * 69 * When CAM_IOSCHED_DYNAMIC is defined, the scheduler is enhanced to dynamically 70 * steer the rate of one type of traffic to help other types of traffic (eg 71 * limit writes when read latency deteriorates on SSDs). 72 */ 73 74 #ifdef CAM_IOSCHED_DYNAMIC 75 76 static bool do_dynamic_iosched = true; 77 SYSCTL_BOOL(_kern_cam_iosched, OID_AUTO, dynamic, CTLFLAG_RD | CTLFLAG_TUN, 78 &do_dynamic_iosched, 1, 79 "Enable Dynamic I/O scheduler optimizations."); 80 81 /* 82 * For an EMA, with an alpha of alpha, we know 83 * alpha = 2 / (N + 1) 84 * or 85 * N = 1 + (2 / alpha) 86 * where N is the number of samples that 86% of the current 87 * EMA is derived from. 88 * 89 * So we invent[*] alpha_bits: 90 * alpha_bits = -log_2(alpha) 91 * alpha = 2^-alpha_bits 92 * So 93 * N = 1 + 2^(alpha_bits + 1) 94 * 95 * The default 9 gives a 1025 lookback for 86% of the data. 96 * For a brief intro: https://en.wikipedia.org/wiki/Moving_average 97 * 98 * [*] Steal from the load average code and many other places. 99 * Note: See computation of EMA and EMVAR for acceptable ranges of alpha. 100 */ 101 static int alpha_bits = 9; 102 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, alpha_bits, CTLFLAG_RW | CTLFLAG_TUN, 103 &alpha_bits, 1, 104 "Bits in EMA's alpha."); 105 106 /* 107 * Different parameters for the buckets of latency we keep track of. These are all 108 * published read-only since at present they are compile time constants. 109 * 110 * Bucket base is the upper bounds of the first latency bucket. It's currently 20us. 111 * With 20 buckets (see below), that leads to a geometric progression with a max size 112 * of 5.2s which is safeily larger than 1s to help diagnose extreme outliers better. 113 */ 114 #ifndef BUCKET_BASE 115 #define BUCKET_BASE ((SBT_1S / 50000) + 1) /* 20us */ 116 #endif 117 static sbintime_t bucket_base = BUCKET_BASE; 118 SYSCTL_SBINTIME_USEC(_kern_cam_iosched, OID_AUTO, bucket_base_us, CTLFLAG_RD, 119 &bucket_base, 120 "Size of the smallest latency bucket"); 121 122 /* 123 * Bucket ratio is the geometric progression for the bucket. For a bucket b_n 124 * the size of bucket b_n+1 is b_n * bucket_ratio / 100. 125 */ 126 static int bucket_ratio = 200; /* Rather hard coded at the moment */ 127 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, bucket_ratio, CTLFLAG_RD, 128 &bucket_ratio, 200, 129 "Latency Bucket Ratio for geometric progression."); 130 131 /* 132 * Number of total buckets. Starting at BUCKET_BASE, each one is a power of 2. 133 */ 134 #ifndef LAT_BUCKETS 135 #define LAT_BUCKETS 20 /* < 20us < 40us ... < 2^(n-1)*20us >= 2^(n-1)*20us */ 136 #endif 137 static int lat_buckets = LAT_BUCKETS; 138 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, buckets, CTLFLAG_RD, 139 &lat_buckets, LAT_BUCKETS, 140 "Total number of latency buckets published"); 141 142 /* 143 * Read bias: how many reads do we favor before scheduling a write 144 * when we have a choice. 145 */ 146 static int default_read_bias = 0; 147 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, read_bias, CTLFLAG_RWTUN, 148 &default_read_bias, 0, 149 "Default read bias for new devices."); 150 151 struct iop_stats; 152 struct cam_iosched_softc; 153 154 int iosched_debug = 0; 155 156 typedef enum { 157 none = 0, /* No limits */ 158 queue_depth, /* Limit how many ops we queue to SIM */ 159 iops, /* Limit # of IOPS to the drive */ 160 bandwidth, /* Limit bandwidth to the drive */ 161 limiter_max 162 } io_limiter; 163 164 static const char *cam_iosched_limiter_names[] = 165 { "none", "queue_depth", "iops", "bandwidth" }; 166 167 /* 168 * Called to initialize the bits of the iop_stats structure relevant to the 169 * limiter. Called just after the limiter is set. 170 */ 171 typedef int l_init_t(struct iop_stats *); 172 173 /* 174 * Called every tick. 175 */ 176 typedef int l_tick_t(struct iop_stats *); 177 178 /* 179 * Called to see if the limiter thinks this IOP can be allowed to 180 * proceed. If so, the limiter assumes that the IOP proceeded 181 * and makes any accounting of it that's needed. 182 */ 183 typedef int l_iop_t(struct iop_stats *, struct bio *); 184 185 /* 186 * Called when an I/O completes so the limiter can update its 187 * accounting. Pending I/Os may complete in any order (even when 188 * sent to the hardware at the same time), so the limiter may not 189 * make any assumptions other than this I/O has completed. If it 190 * returns 1, then xpt_schedule() needs to be called again. 191 */ 192 typedef int l_iodone_t(struct iop_stats *, struct bio *); 193 194 static l_iop_t cam_iosched_qd_iop; 195 static l_iop_t cam_iosched_qd_caniop; 196 static l_iodone_t cam_iosched_qd_iodone; 197 198 static l_init_t cam_iosched_iops_init; 199 static l_tick_t cam_iosched_iops_tick; 200 static l_iop_t cam_iosched_iops_caniop; 201 static l_iop_t cam_iosched_iops_iop; 202 203 static l_init_t cam_iosched_bw_init; 204 static l_tick_t cam_iosched_bw_tick; 205 static l_iop_t cam_iosched_bw_caniop; 206 static l_iop_t cam_iosched_bw_iop; 207 208 struct limswitch { 209 l_init_t *l_init; 210 l_tick_t *l_tick; 211 l_iop_t *l_iop; 212 l_iop_t *l_caniop; 213 l_iodone_t *l_iodone; 214 } limsw[] = 215 { 216 { /* none */ 217 .l_init = NULL, 218 .l_tick = NULL, 219 .l_iop = NULL, 220 .l_iodone= NULL, 221 }, 222 { /* queue_depth */ 223 .l_init = NULL, 224 .l_tick = NULL, 225 .l_caniop = cam_iosched_qd_caniop, 226 .l_iop = cam_iosched_qd_iop, 227 .l_iodone= cam_iosched_qd_iodone, 228 }, 229 { /* iops */ 230 .l_init = cam_iosched_iops_init, 231 .l_tick = cam_iosched_iops_tick, 232 .l_caniop = cam_iosched_iops_caniop, 233 .l_iop = cam_iosched_iops_iop, 234 .l_iodone= NULL, 235 }, 236 { /* bandwidth */ 237 .l_init = cam_iosched_bw_init, 238 .l_tick = cam_iosched_bw_tick, 239 .l_caniop = cam_iosched_bw_caniop, 240 .l_iop = cam_iosched_bw_iop, 241 .l_iodone= NULL, 242 }, 243 }; 244 245 struct iop_stats { 246 /* 247 * sysctl state for this subnode. 248 */ 249 struct sysctl_ctx_list sysctl_ctx; 250 struct sysctl_oid *sysctl_tree; 251 252 /* 253 * Information about the current rate limiters, if any 254 */ 255 io_limiter limiter; /* How are I/Os being limited */ 256 int min; /* Low range of limit */ 257 int max; /* High range of limit */ 258 int current; /* Current rate limiter */ 259 int l_value1; /* per-limiter scratch value 1. */ 260 int l_value2; /* per-limiter scratch value 2. */ 261 262 /* 263 * Debug information about counts of I/Os that have gone through the 264 * scheduler. 265 */ 266 int pending; /* I/Os pending in the hardware */ 267 int queued; /* number currently in the queue */ 268 int total; /* Total for all time -- wraps */ 269 int in; /* number queued all time -- wraps */ 270 int out; /* number completed all time -- wraps */ 271 int errs; /* Number of I/Os completed with error -- wraps */ 272 273 /* 274 * Statistics on different bits of the process. 275 */ 276 /* Exp Moving Average, see alpha_bits for more details */ 277 sbintime_t ema; 278 sbintime_t emvar; 279 sbintime_t sd; /* Last computed sd */ 280 281 uint32_t state_flags; 282 #define IOP_RATE_LIMITED 1u 283 284 uint64_t latencies[LAT_BUCKETS]; 285 286 struct cam_iosched_softc *softc; 287 }; 288 289 typedef enum { 290 set_max = 0, /* current = max */ 291 read_latency, /* Steer read latency by throttling writes */ 292 cl_max /* Keep last */ 293 } control_type; 294 295 static const char *cam_iosched_control_type_names[] = 296 { "set_max", "read_latency" }; 297 298 struct control_loop { 299 /* 300 * sysctl state for this subnode. 301 */ 302 struct sysctl_ctx_list sysctl_ctx; 303 struct sysctl_oid *sysctl_tree; 304 305 sbintime_t next_steer; /* Time of next steer */ 306 sbintime_t steer_interval; /* How often do we steer? */ 307 sbintime_t lolat; 308 sbintime_t hilat; 309 int alpha; 310 control_type type; /* What type of control? */ 311 int last_count; /* Last I/O count */ 312 313 struct cam_iosched_softc *softc; 314 }; 315 316 #endif 317 318 struct cam_iosched_softc { 319 struct bio_queue_head bio_queue; 320 struct bio_queue_head trim_queue; 321 /* scheduler flags < 16, user flags >= 16 */ 322 uint32_t flags; 323 int sort_io_queue; 324 int trim_goal; /* # of trims to queue before sending */ 325 int trim_ticks; /* Max ticks to hold trims */ 326 int last_trim_tick; /* Last 'tick' time ld a trim */ 327 int queued_trims; /* Number of trims in the queue */ 328 #ifdef CAM_IOSCHED_DYNAMIC 329 int read_bias; /* Read bias setting */ 330 int current_read_bias; /* Current read bias state */ 331 int total_ticks; 332 int load; /* EMA of 'load average' of disk / 2^16 */ 333 334 struct bio_queue_head write_queue; 335 struct iop_stats read_stats, write_stats, trim_stats; 336 struct sysctl_ctx_list sysctl_ctx; 337 struct sysctl_oid *sysctl_tree; 338 339 int quanta; /* Number of quanta per second */ 340 struct callout ticker; /* Callout for our quota system */ 341 struct cam_periph *periph; /* cam periph associated with this device */ 342 uint32_t this_frac; /* Fraction of a second (1024ths) for this tick */ 343 sbintime_t last_time; /* Last time we ticked */ 344 struct control_loop cl; 345 sbintime_t max_lat; /* when != 0, if iop latency > max_lat, call max_lat_fcn */ 346 cam_iosched_latfcn_t latfcn; 347 void *latarg; 348 #endif 349 }; 350 351 #ifdef CAM_IOSCHED_DYNAMIC 352 /* 353 * helper functions to call the limsw functions. 354 */ 355 static int 356 cam_iosched_limiter_init(struct iop_stats *ios) 357 { 358 int lim = ios->limiter; 359 360 /* maybe this should be a kassert */ 361 if (lim < none || lim >= limiter_max) 362 return EINVAL; 363 364 if (limsw[lim].l_init) 365 return limsw[lim].l_init(ios); 366 367 return 0; 368 } 369 370 static int 371 cam_iosched_limiter_tick(struct iop_stats *ios) 372 { 373 int lim = ios->limiter; 374 375 /* maybe this should be a kassert */ 376 if (lim < none || lim >= limiter_max) 377 return EINVAL; 378 379 if (limsw[lim].l_tick) 380 return limsw[lim].l_tick(ios); 381 382 return 0; 383 } 384 385 static int 386 cam_iosched_limiter_iop(struct iop_stats *ios, struct bio *bp) 387 { 388 int lim = ios->limiter; 389 390 /* maybe this should be a kassert */ 391 if (lim < none || lim >= limiter_max) 392 return EINVAL; 393 394 if (limsw[lim].l_iop) 395 return limsw[lim].l_iop(ios, bp); 396 397 return 0; 398 } 399 400 static int 401 cam_iosched_limiter_caniop(struct iop_stats *ios, struct bio *bp) 402 { 403 int lim = ios->limiter; 404 405 /* maybe this should be a kassert */ 406 if (lim < none || lim >= limiter_max) 407 return EINVAL; 408 409 if (limsw[lim].l_caniop) 410 return limsw[lim].l_caniop(ios, bp); 411 412 return 0; 413 } 414 415 static int 416 cam_iosched_limiter_iodone(struct iop_stats *ios, struct bio *bp) 417 { 418 int lim = ios->limiter; 419 420 /* maybe this should be a kassert */ 421 if (lim < none || lim >= limiter_max) 422 return 0; 423 424 if (limsw[lim].l_iodone) 425 return limsw[lim].l_iodone(ios, bp); 426 427 return 0; 428 } 429 430 /* 431 * Functions to implement the different kinds of limiters 432 */ 433 434 static int 435 cam_iosched_qd_iop(struct iop_stats *ios, struct bio *bp) 436 { 437 438 if (ios->current <= 0 || ios->pending < ios->current) 439 return 0; 440 441 return EAGAIN; 442 } 443 444 static int 445 cam_iosched_qd_caniop(struct iop_stats *ios, struct bio *bp) 446 { 447 448 if (ios->current <= 0 || ios->pending < ios->current) 449 return 0; 450 451 return EAGAIN; 452 } 453 454 static int 455 cam_iosched_qd_iodone(struct iop_stats *ios, struct bio *bp) 456 { 457 458 if (ios->current <= 0 || ios->pending != ios->current) 459 return 0; 460 461 return 1; 462 } 463 464 static int 465 cam_iosched_iops_init(struct iop_stats *ios) 466 { 467 468 ios->l_value1 = ios->current / ios->softc->quanta; 469 if (ios->l_value1 <= 0) 470 ios->l_value1 = 1; 471 ios->l_value2 = 0; 472 473 return 0; 474 } 475 476 static int 477 cam_iosched_iops_tick(struct iop_stats *ios) 478 { 479 int new_ios; 480 481 /* 482 * Allow at least one IO per tick until all 483 * the IOs for this interval have been spent. 484 */ 485 new_ios = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16); 486 if (new_ios < 1 && ios->l_value2 < ios->current) { 487 new_ios = 1; 488 ios->l_value2++; 489 } 490 491 /* 492 * If this a new accounting interval, discard any "unspent" ios 493 * granted in the previous interval. Otherwise add the new ios to 494 * the previously granted ones that haven't been spent yet. 495 */ 496 if ((ios->softc->total_ticks % ios->softc->quanta) == 0) { 497 ios->l_value1 = new_ios; 498 ios->l_value2 = 1; 499 } else { 500 ios->l_value1 += new_ios; 501 } 502 503 return 0; 504 } 505 506 static int 507 cam_iosched_iops_caniop(struct iop_stats *ios, struct bio *bp) 508 { 509 510 /* 511 * So if we have any more IOPs left, allow it, 512 * otherwise wait. If current iops is 0, treat that 513 * as unlimited as a failsafe. 514 */ 515 if (ios->current > 0 && ios->l_value1 <= 0) 516 return EAGAIN; 517 return 0; 518 } 519 520 static int 521 cam_iosched_iops_iop(struct iop_stats *ios, struct bio *bp) 522 { 523 int rv; 524 525 rv = cam_iosched_limiter_caniop(ios, bp); 526 if (rv == 0) 527 ios->l_value1--; 528 529 return rv; 530 } 531 532 static int 533 cam_iosched_bw_init(struct iop_stats *ios) 534 { 535 536 /* ios->current is in kB/s, so scale to bytes */ 537 ios->l_value1 = ios->current * 1000 / ios->softc->quanta; 538 539 return 0; 540 } 541 542 static int 543 cam_iosched_bw_tick(struct iop_stats *ios) 544 { 545 int bw; 546 547 /* 548 * If we're in the hole for available quota from 549 * the last time, then add the quantum for this. 550 * If we have any left over from last quantum, 551 * then too bad, that's lost. Also, ios->current 552 * is in kB/s, so scale. 553 * 554 * We also allow up to 4 quanta of credits to 555 * accumulate to deal with burstiness. 4 is extremely 556 * arbitrary. 557 */ 558 bw = (int)((ios->current * 1000ull * (uint64_t)ios->softc->this_frac) >> 16); 559 if (ios->l_value1 < bw * 4) 560 ios->l_value1 += bw; 561 562 return 0; 563 } 564 565 static int 566 cam_iosched_bw_caniop(struct iop_stats *ios, struct bio *bp) 567 { 568 /* 569 * So if we have any more bw quota left, allow it, 570 * otherwise wait. Note, we'll go negative and that's 571 * OK. We'll just get a little less next quota. 572 * 573 * Note on going negative: that allows us to process 574 * requests in order better, since we won't allow 575 * shorter reads to get around the long one that we 576 * don't have the quota to do just yet. It also prevents 577 * starvation by being a little more permissive about 578 * what we let through this quantum (to prevent the 579 * starvation), at the cost of getting a little less 580 * next quantum. 581 * 582 * Also note that if the current limit is <= 0, 583 * we treat it as unlimited as a failsafe. 584 */ 585 if (ios->current > 0 && ios->l_value1 <= 0) 586 return EAGAIN; 587 588 return 0; 589 } 590 591 static int 592 cam_iosched_bw_iop(struct iop_stats *ios, struct bio *bp) 593 { 594 int rv; 595 596 rv = cam_iosched_limiter_caniop(ios, bp); 597 if (rv == 0) 598 ios->l_value1 -= bp->bio_length; 599 600 return rv; 601 } 602 603 static void cam_iosched_cl_maybe_steer(struct control_loop *clp); 604 605 static void 606 cam_iosched_ticker(void *arg) 607 { 608 struct cam_iosched_softc *isc = arg; 609 sbintime_t now, delta; 610 int pending; 611 612 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc); 613 614 now = sbinuptime(); 615 delta = now - isc->last_time; 616 isc->this_frac = (uint32_t)delta >> 16; /* Note: discards seconds -- should be 0 harmless if not */ 617 isc->last_time = now; 618 619 cam_iosched_cl_maybe_steer(&isc->cl); 620 621 cam_iosched_limiter_tick(&isc->read_stats); 622 cam_iosched_limiter_tick(&isc->write_stats); 623 cam_iosched_limiter_tick(&isc->trim_stats); 624 625 cam_iosched_schedule(isc, isc->periph); 626 627 /* 628 * isc->load is an EMA of the pending I/Os at each tick. The number of 629 * pending I/Os is the sum of the I/Os queued to the hardware, and those 630 * in the software queue that could be queued to the hardware if there 631 * were slots. 632 * 633 * ios_stats.pending is a count of requests in the SIM right now for 634 * each of these types of I/O. So the total pending count is the sum of 635 * these I/Os and the sum of the queued I/Os still in the software queue 636 * for those operations that aren't being rate limited at the moment. 637 * 638 * The reason for the rate limiting bit is because those I/Os 639 * aren't part of the software queued load (since we could 640 * give them to hardware, but choose not to). 641 * 642 * Note: due to a bug in counting pending TRIM in the device, we 643 * don't include them in this count. We count each BIO_DELETE in 644 * the pending count, but the periph drivers collapse them down 645 * into one TRIM command. That one trim command gets the completion 646 * so the counts get off. 647 */ 648 pending = isc->read_stats.pending + isc->write_stats.pending /* + isc->trim_stats.pending */; 649 pending += !!(isc->read_stats.state_flags & IOP_RATE_LIMITED) * isc->read_stats.queued + 650 !!(isc->write_stats.state_flags & IOP_RATE_LIMITED) * isc->write_stats.queued /* + 651 !!(isc->trim_stats.state_flags & IOP_RATE_LIMITED) * isc->trim_stats.queued */ ; 652 pending <<= 16; 653 pending /= isc->periph->path->device->ccbq.total_openings; 654 655 isc->load = (pending + (isc->load << 13) - isc->load) >> 13; /* see above: 13 -> 16139 / 200/s = ~81s ~1 minute */ 656 657 isc->total_ticks++; 658 } 659 660 static void 661 cam_iosched_cl_init(struct control_loop *clp, struct cam_iosched_softc *isc) 662 { 663 664 clp->next_steer = sbinuptime(); 665 clp->softc = isc; 666 clp->steer_interval = SBT_1S * 5; /* Let's start out steering every 5s */ 667 clp->lolat = 5 * SBT_1MS; 668 clp->hilat = 15 * SBT_1MS; 669 clp->alpha = 20; /* Alpha == gain. 20 = .2 */ 670 clp->type = set_max; 671 } 672 673 static void 674 cam_iosched_cl_maybe_steer(struct control_loop *clp) 675 { 676 struct cam_iosched_softc *isc; 677 sbintime_t now, lat; 678 int old; 679 680 isc = clp->softc; 681 now = isc->last_time; 682 if (now < clp->next_steer) 683 return; 684 685 clp->next_steer = now + clp->steer_interval; 686 switch (clp->type) { 687 case set_max: 688 if (isc->write_stats.current != isc->write_stats.max) 689 printf("Steering write from %d kBps to %d kBps\n", 690 isc->write_stats.current, isc->write_stats.max); 691 isc->read_stats.current = isc->read_stats.max; 692 isc->write_stats.current = isc->write_stats.max; 693 isc->trim_stats.current = isc->trim_stats.max; 694 break; 695 case read_latency: 696 old = isc->write_stats.current; 697 lat = isc->read_stats.ema; 698 /* 699 * Simple PLL-like engine. Since we're steering to a range for 700 * the SP (set point) that makes things a little more 701 * complicated. In addition, we're not directly controlling our 702 * PV (process variable), the read latency, but instead are 703 * manipulating the write bandwidth limit for our MV 704 * (manipulation variable), analysis of this code gets a bit 705 * messy. Also, the MV is a very noisy control surface for read 706 * latency since it is affected by many hidden processes inside 707 * the device which change how responsive read latency will be 708 * in reaction to changes in write bandwidth. Unlike the classic 709 * boiler control PLL. this may result in over-steering while 710 * the SSD takes its time to react to the new, lower load. This 711 * is why we use a relatively low alpha of between .1 and .25 to 712 * compensate for this effect. At .1, it takes ~22 steering 713 * intervals to back off by a factor of 10. At .2 it only takes 714 * ~10. At .25 it only takes ~8. However some preliminary data 715 * from the SSD drives suggests a reasponse time in 10's of 716 * seconds before latency drops regardless of the new write 717 * rate. Careful observation will be required to tune this 718 * effectively. 719 * 720 * Also, when there's no read traffic, we jack up the write 721 * limit too regardless of the last read latency. 10 is 722 * somewhat arbitrary. 723 */ 724 if (lat < clp->lolat || isc->read_stats.total - clp->last_count < 10) 725 isc->write_stats.current = isc->write_stats.current * 726 (100 + clp->alpha) / 100; /* Scale up */ 727 else if (lat > clp->hilat) 728 isc->write_stats.current = isc->write_stats.current * 729 (100 - clp->alpha) / 100; /* Scale down */ 730 clp->last_count = isc->read_stats.total; 731 732 /* 733 * Even if we don't steer, per se, enforce the min/max limits as 734 * those may have changed. 735 */ 736 if (isc->write_stats.current < isc->write_stats.min) 737 isc->write_stats.current = isc->write_stats.min; 738 if (isc->write_stats.current > isc->write_stats.max) 739 isc->write_stats.current = isc->write_stats.max; 740 if (old != isc->write_stats.current && iosched_debug) 741 printf("Steering write from %d kBps to %d kBps due to latency of %jdus\n", 742 old, isc->write_stats.current, 743 (uintmax_t)((uint64_t)1000000 * (uint32_t)lat) >> 32); 744 break; 745 case cl_max: 746 break; 747 } 748 } 749 #endif 750 751 /* 752 * Trim or similar currently pending completion. Should only be set for 753 * those drivers wishing only one Trim active at a time. 754 */ 755 #define CAM_IOSCHED_FLAG_TRIM_ACTIVE (1ul << 0) 756 /* Callout active, and needs to be torn down */ 757 #define CAM_IOSCHED_FLAG_CALLOUT_ACTIVE (1ul << 1) 758 759 /* Periph drivers set these flags to indicate work */ 760 #define CAM_IOSCHED_FLAG_WORK_FLAGS ((0xffffu) << 16) 761 762 #ifdef CAM_IOSCHED_DYNAMIC 763 static void 764 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 765 sbintime_t sim_latency, int cmd, size_t size); 766 #endif 767 768 static inline bool 769 cam_iosched_has_flagged_work(struct cam_iosched_softc *isc) 770 { 771 return !!(isc->flags & CAM_IOSCHED_FLAG_WORK_FLAGS); 772 } 773 774 static inline bool 775 cam_iosched_has_io(struct cam_iosched_softc *isc) 776 { 777 #ifdef CAM_IOSCHED_DYNAMIC 778 if (do_dynamic_iosched) { 779 struct bio *rbp = bioq_first(&isc->bio_queue); 780 struct bio *wbp = bioq_first(&isc->write_queue); 781 bool can_write = wbp != NULL && 782 cam_iosched_limiter_caniop(&isc->write_stats, wbp) == 0; 783 bool can_read = rbp != NULL && 784 cam_iosched_limiter_caniop(&isc->read_stats, rbp) == 0; 785 if (iosched_debug > 2) { 786 printf("can write %d: pending_writes %d max_writes %d\n", can_write, isc->write_stats.pending, isc->write_stats.max); 787 printf("can read %d: read_stats.pending %d max_reads %d\n", can_read, isc->read_stats.pending, isc->read_stats.max); 788 printf("Queued reads %d writes %d\n", isc->read_stats.queued, isc->write_stats.queued); 789 } 790 return can_read || can_write; 791 } 792 #endif 793 return bioq_first(&isc->bio_queue) != NULL; 794 } 795 796 static inline bool 797 cam_iosched_has_more_trim(struct cam_iosched_softc *isc) 798 { 799 struct bio *bp; 800 801 bp = bioq_first(&isc->trim_queue); 802 #ifdef CAM_IOSCHED_DYNAMIC 803 if (do_dynamic_iosched) { 804 /* 805 * If we're limiting trims, then defer action on trims 806 * for a bit. 807 */ 808 if (bp == NULL || cam_iosched_limiter_caniop(&isc->trim_stats, bp) != 0) 809 return false; 810 } 811 #endif 812 813 /* 814 * If we've set a trim_goal, then if we exceed that allow trims 815 * to be passed back to the driver. If we've also set a tick timeout 816 * allow trims back to the driver. Otherwise, don't allow trims yet. 817 */ 818 if (isc->trim_goal > 0) { 819 if (isc->queued_trims >= isc->trim_goal) 820 return true; 821 if (isc->queued_trims > 0 && 822 isc->trim_ticks > 0 && 823 ticks - isc->last_trim_tick > isc->trim_ticks) 824 return true; 825 return false; 826 } 827 828 /* NB: Should perhaps have a max trim active independent of I/O limiters */ 829 return !(isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) && bp != NULL; 830 } 831 832 #define cam_iosched_sort_queue(isc) ((isc)->sort_io_queue >= 0 ? \ 833 (isc)->sort_io_queue : cam_sort_io_queues) 834 835 static inline bool 836 cam_iosched_has_work(struct cam_iosched_softc *isc) 837 { 838 #ifdef CAM_IOSCHED_DYNAMIC 839 if (iosched_debug > 2) 840 printf("has work: %d %d %d\n", cam_iosched_has_io(isc), 841 cam_iosched_has_more_trim(isc), 842 cam_iosched_has_flagged_work(isc)); 843 #endif 844 845 return cam_iosched_has_io(isc) || 846 cam_iosched_has_more_trim(isc) || 847 cam_iosched_has_flagged_work(isc); 848 } 849 850 #ifdef CAM_IOSCHED_DYNAMIC 851 static void 852 cam_iosched_iop_stats_init(struct cam_iosched_softc *isc, struct iop_stats *ios) 853 { 854 855 ios->limiter = none; 856 ios->in = 0; 857 ios->max = ios->current = 300000; 858 ios->min = 1; 859 ios->out = 0; 860 ios->errs = 0; 861 ios->pending = 0; 862 ios->queued = 0; 863 ios->total = 0; 864 ios->ema = 0; 865 ios->emvar = 0; 866 ios->softc = isc; 867 cam_iosched_limiter_init(ios); 868 } 869 870 static int 871 cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS) 872 { 873 char buf[16]; 874 struct iop_stats *ios; 875 struct cam_iosched_softc *isc; 876 int value, i, error; 877 const char *p; 878 879 ios = arg1; 880 isc = ios->softc; 881 value = ios->limiter; 882 if (value < none || value >= limiter_max) 883 p = "UNKNOWN"; 884 else 885 p = cam_iosched_limiter_names[value]; 886 887 strlcpy(buf, p, sizeof(buf)); 888 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 889 if (error != 0 || req->newptr == NULL) 890 return error; 891 892 cam_periph_lock(isc->periph); 893 894 for (i = none; i < limiter_max; i++) { 895 if (strcmp(buf, cam_iosched_limiter_names[i]) != 0) 896 continue; 897 ios->limiter = i; 898 error = cam_iosched_limiter_init(ios); 899 if (error != 0) { 900 ios->limiter = value; 901 cam_periph_unlock(isc->periph); 902 return error; 903 } 904 /* Note: disk load averate requires ticker to be always running */ 905 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc); 906 isc->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 907 908 cam_periph_unlock(isc->periph); 909 return 0; 910 } 911 912 cam_periph_unlock(isc->periph); 913 return EINVAL; 914 } 915 916 static int 917 cam_iosched_control_type_sysctl(SYSCTL_HANDLER_ARGS) 918 { 919 char buf[16]; 920 struct control_loop *clp; 921 struct cam_iosched_softc *isc; 922 int value, i, error; 923 const char *p; 924 925 clp = arg1; 926 isc = clp->softc; 927 value = clp->type; 928 if (value < none || value >= cl_max) 929 p = "UNKNOWN"; 930 else 931 p = cam_iosched_control_type_names[value]; 932 933 strlcpy(buf, p, sizeof(buf)); 934 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 935 if (error != 0 || req->newptr == NULL) 936 return error; 937 938 for (i = set_max; i < cl_max; i++) { 939 if (strcmp(buf, cam_iosched_control_type_names[i]) != 0) 940 continue; 941 cam_periph_lock(isc->periph); 942 clp->type = i; 943 cam_periph_unlock(isc->periph); 944 return 0; 945 } 946 947 return EINVAL; 948 } 949 950 static int 951 cam_iosched_sbintime_sysctl(SYSCTL_HANDLER_ARGS) 952 { 953 char buf[16]; 954 sbintime_t value; 955 int error; 956 uint64_t us; 957 958 value = *(sbintime_t *)arg1; 959 us = (uint64_t)value / SBT_1US; 960 snprintf(buf, sizeof(buf), "%ju", (intmax_t)us); 961 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 962 if (error != 0 || req->newptr == NULL) 963 return error; 964 us = strtoul(buf, NULL, 10); 965 if (us == 0) 966 return EINVAL; 967 *(sbintime_t *)arg1 = us * SBT_1US; 968 return 0; 969 } 970 971 static int 972 cam_iosched_sysctl_latencies(SYSCTL_HANDLER_ARGS) 973 { 974 int i, error; 975 struct sbuf sb; 976 uint64_t *latencies; 977 978 latencies = arg1; 979 sbuf_new_for_sysctl(&sb, NULL, LAT_BUCKETS * 16, req); 980 981 for (i = 0; i < LAT_BUCKETS - 1; i++) 982 sbuf_printf(&sb, "%jd,", (intmax_t)latencies[i]); 983 sbuf_printf(&sb, "%jd", (intmax_t)latencies[LAT_BUCKETS - 1]); 984 error = sbuf_finish(&sb); 985 sbuf_delete(&sb); 986 987 return (error); 988 } 989 990 static int 991 cam_iosched_quanta_sysctl(SYSCTL_HANDLER_ARGS) 992 { 993 int *quanta; 994 int error, value; 995 996 quanta = (unsigned *)arg1; 997 value = *quanta; 998 999 error = sysctl_handle_int(oidp, (int *)&value, 0, req); 1000 if ((error != 0) || (req->newptr == NULL)) 1001 return (error); 1002 1003 if (value < 1 || value > hz) 1004 return (EINVAL); 1005 1006 *quanta = value; 1007 1008 return (0); 1009 } 1010 1011 static void 1012 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct iop_stats *ios, char *name) 1013 { 1014 struct sysctl_oid_list *n; 1015 struct sysctl_ctx_list *ctx; 1016 1017 ios->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1018 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, name, 1019 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, name); 1020 n = SYSCTL_CHILDREN(ios->sysctl_tree); 1021 ctx = &ios->sysctl_ctx; 1022 1023 SYSCTL_ADD_UQUAD(ctx, n, 1024 OID_AUTO, "ema", CTLFLAG_RD, 1025 &ios->ema, 1026 "Fast Exponentially Weighted Moving Average"); 1027 SYSCTL_ADD_UQUAD(ctx, n, 1028 OID_AUTO, "emvar", CTLFLAG_RD, 1029 &ios->emvar, 1030 "Fast Exponentially Weighted Moving Variance"); 1031 1032 SYSCTL_ADD_INT(ctx, n, 1033 OID_AUTO, "pending", CTLFLAG_RD, 1034 &ios->pending, 0, 1035 "Instantaneous # of pending transactions"); 1036 SYSCTL_ADD_INT(ctx, n, 1037 OID_AUTO, "count", CTLFLAG_RD, 1038 &ios->total, 0, 1039 "# of transactions submitted to hardware"); 1040 SYSCTL_ADD_INT(ctx, n, 1041 OID_AUTO, "queued", CTLFLAG_RD, 1042 &ios->queued, 0, 1043 "# of transactions in the queue"); 1044 SYSCTL_ADD_INT(ctx, n, 1045 OID_AUTO, "in", CTLFLAG_RD, 1046 &ios->in, 0, 1047 "# of transactions queued to driver"); 1048 SYSCTL_ADD_INT(ctx, n, 1049 OID_AUTO, "out", CTLFLAG_RD, 1050 &ios->out, 0, 1051 "# of transactions completed (including with error)"); 1052 SYSCTL_ADD_INT(ctx, n, 1053 OID_AUTO, "errs", CTLFLAG_RD, 1054 &ios->errs, 0, 1055 "# of transactions completed with an error"); 1056 1057 SYSCTL_ADD_PROC(ctx, n, 1058 OID_AUTO, "limiter", 1059 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 1060 ios, 0, cam_iosched_limiter_sysctl, "A", 1061 "Current limiting type."); 1062 SYSCTL_ADD_INT(ctx, n, 1063 OID_AUTO, "min", CTLFLAG_RW, 1064 &ios->min, 0, 1065 "min resource"); 1066 SYSCTL_ADD_INT(ctx, n, 1067 OID_AUTO, "max", CTLFLAG_RW, 1068 &ios->max, 0, 1069 "max resource"); 1070 SYSCTL_ADD_INT(ctx, n, 1071 OID_AUTO, "current", CTLFLAG_RW, 1072 &ios->current, 0, 1073 "current resource"); 1074 1075 SYSCTL_ADD_PROC(ctx, n, 1076 OID_AUTO, "latencies", 1077 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, 1078 &ios->latencies, 0, 1079 cam_iosched_sysctl_latencies, "A", 1080 "Array of power of 2 latency from 1ms to 1.024s"); 1081 } 1082 1083 static void 1084 cam_iosched_iop_stats_fini(struct iop_stats *ios) 1085 { 1086 if (ios->sysctl_tree) 1087 if (sysctl_ctx_free(&ios->sysctl_ctx) != 0) 1088 printf("can't remove iosched sysctl stats context\n"); 1089 } 1090 1091 static void 1092 cam_iosched_cl_sysctl_init(struct cam_iosched_softc *isc) 1093 { 1094 struct sysctl_oid_list *n; 1095 struct sysctl_ctx_list *ctx; 1096 struct control_loop *clp; 1097 1098 clp = &isc->cl; 1099 clp->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1100 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, "control", 1101 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "Control loop info"); 1102 n = SYSCTL_CHILDREN(clp->sysctl_tree); 1103 ctx = &clp->sysctl_ctx; 1104 1105 SYSCTL_ADD_PROC(ctx, n, 1106 OID_AUTO, "type", 1107 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 1108 clp, 0, cam_iosched_control_type_sysctl, "A", 1109 "Control loop algorithm"); 1110 SYSCTL_ADD_PROC(ctx, n, 1111 OID_AUTO, "steer_interval", 1112 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 1113 &clp->steer_interval, 0, cam_iosched_sbintime_sysctl, "A", 1114 "How often to steer (in us)"); 1115 SYSCTL_ADD_PROC(ctx, n, 1116 OID_AUTO, "lolat", 1117 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 1118 &clp->lolat, 0, cam_iosched_sbintime_sysctl, "A", 1119 "Low water mark for Latency (in us)"); 1120 SYSCTL_ADD_PROC(ctx, n, 1121 OID_AUTO, "hilat", 1122 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 1123 &clp->hilat, 0, cam_iosched_sbintime_sysctl, "A", 1124 "Hi water mark for Latency (in us)"); 1125 SYSCTL_ADD_INT(ctx, n, 1126 OID_AUTO, "alpha", CTLFLAG_RW, 1127 &clp->alpha, 0, 1128 "Alpha for PLL (x100) aka gain"); 1129 } 1130 1131 static void 1132 cam_iosched_cl_sysctl_fini(struct control_loop *clp) 1133 { 1134 if (clp->sysctl_tree) 1135 if (sysctl_ctx_free(&clp->sysctl_ctx) != 0) 1136 printf("can't remove iosched sysctl control loop context\n"); 1137 } 1138 #endif 1139 1140 /* 1141 * Allocate the iosched structure. This also insulates callers from knowing 1142 * sizeof struct cam_iosched_softc. 1143 */ 1144 int 1145 cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph) 1146 { 1147 1148 *iscp = malloc(sizeof(**iscp), M_CAMSCHED, M_NOWAIT | M_ZERO); 1149 if (*iscp == NULL) 1150 return ENOMEM; 1151 #ifdef CAM_IOSCHED_DYNAMIC 1152 if (iosched_debug) 1153 printf("CAM IOSCHEDULER Allocating entry at %p\n", *iscp); 1154 #endif 1155 (*iscp)->sort_io_queue = -1; 1156 bioq_init(&(*iscp)->bio_queue); 1157 bioq_init(&(*iscp)->trim_queue); 1158 #ifdef CAM_IOSCHED_DYNAMIC 1159 if (do_dynamic_iosched) { 1160 bioq_init(&(*iscp)->write_queue); 1161 (*iscp)->read_bias = default_read_bias; 1162 (*iscp)->current_read_bias = 0; 1163 (*iscp)->quanta = min(hz, 200); 1164 cam_iosched_iop_stats_init(*iscp, &(*iscp)->read_stats); 1165 cam_iosched_iop_stats_init(*iscp, &(*iscp)->write_stats); 1166 cam_iosched_iop_stats_init(*iscp, &(*iscp)->trim_stats); 1167 (*iscp)->trim_stats.max = 1; /* Trims are special: one at a time for now */ 1168 (*iscp)->last_time = sbinuptime(); 1169 callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0); 1170 (*iscp)->periph = periph; 1171 cam_iosched_cl_init(&(*iscp)->cl, *iscp); 1172 callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta, cam_iosched_ticker, *iscp); 1173 (*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1174 } 1175 #endif 1176 1177 return 0; 1178 } 1179 1180 /* 1181 * Reclaim all used resources. This assumes that other folks have 1182 * drained the requests in the hardware. Maybe an unwise assumption. 1183 */ 1184 void 1185 cam_iosched_fini(struct cam_iosched_softc *isc) 1186 { 1187 if (isc) { 1188 cam_iosched_flush(isc, NULL, ENXIO); 1189 #ifdef CAM_IOSCHED_DYNAMIC 1190 cam_iosched_iop_stats_fini(&isc->read_stats); 1191 cam_iosched_iop_stats_fini(&isc->write_stats); 1192 cam_iosched_iop_stats_fini(&isc->trim_stats); 1193 cam_iosched_cl_sysctl_fini(&isc->cl); 1194 if (isc->sysctl_tree) 1195 if (sysctl_ctx_free(&isc->sysctl_ctx) != 0) 1196 printf("can't remove iosched sysctl stats context\n"); 1197 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) { 1198 callout_drain(&isc->ticker); 1199 isc->flags &= ~ CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1200 } 1201 #endif 1202 free(isc, M_CAMSCHED); 1203 } 1204 } 1205 1206 /* 1207 * After we're sure we're attaching a device, go ahead and add 1208 * hooks for any sysctl we may wish to honor. 1209 */ 1210 void cam_iosched_sysctl_init(struct cam_iosched_softc *isc, 1211 struct sysctl_ctx_list *ctx, struct sysctl_oid *node) 1212 { 1213 struct sysctl_oid_list *n; 1214 1215 n = SYSCTL_CHILDREN(node); 1216 SYSCTL_ADD_INT(ctx, n, 1217 OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE, 1218 &isc->sort_io_queue, 0, 1219 "Sort IO queue to try and optimise disk access patterns"); 1220 SYSCTL_ADD_INT(ctx, n, 1221 OID_AUTO, "trim_goal", CTLFLAG_RW, 1222 &isc->trim_goal, 0, 1223 "Number of trims to try to accumulate before sending to hardware"); 1224 SYSCTL_ADD_INT(ctx, n, 1225 OID_AUTO, "trim_ticks", CTLFLAG_RW, 1226 &isc->trim_goal, 0, 1227 "IO Schedul qaunta to hold back trims for when accumulating"); 1228 1229 #ifdef CAM_IOSCHED_DYNAMIC 1230 if (!do_dynamic_iosched) 1231 return; 1232 1233 isc->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1234 SYSCTL_CHILDREN(node), OID_AUTO, "iosched", 1235 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "I/O scheduler statistics"); 1236 n = SYSCTL_CHILDREN(isc->sysctl_tree); 1237 ctx = &isc->sysctl_ctx; 1238 1239 cam_iosched_iop_stats_sysctl_init(isc, &isc->read_stats, "read"); 1240 cam_iosched_iop_stats_sysctl_init(isc, &isc->write_stats, "write"); 1241 cam_iosched_iop_stats_sysctl_init(isc, &isc->trim_stats, "trim"); 1242 cam_iosched_cl_sysctl_init(isc); 1243 1244 SYSCTL_ADD_INT(ctx, n, 1245 OID_AUTO, "read_bias", CTLFLAG_RW, 1246 &isc->read_bias, default_read_bias, 1247 "How biased towards read should we be independent of limits"); 1248 1249 SYSCTL_ADD_PROC(ctx, n, 1250 OID_AUTO, "quanta", CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 1251 &isc->quanta, 0, cam_iosched_quanta_sysctl, "I", 1252 "How many quanta per second do we slice the I/O up into"); 1253 1254 SYSCTL_ADD_INT(ctx, n, 1255 OID_AUTO, "total_ticks", CTLFLAG_RD, 1256 &isc->total_ticks, 0, 1257 "Total number of ticks we've done"); 1258 1259 SYSCTL_ADD_INT(ctx, n, 1260 OID_AUTO, "load", CTLFLAG_RD, 1261 &isc->load, 0, 1262 "scaled load average / 100"); 1263 1264 SYSCTL_ADD_U64(ctx, n, 1265 OID_AUTO, "latency_trigger", CTLFLAG_RW, 1266 &isc->max_lat, 0, 1267 "Latency treshold to trigger callbacks"); 1268 #endif 1269 } 1270 1271 void 1272 cam_iosched_set_latfcn(struct cam_iosched_softc *isc, 1273 cam_iosched_latfcn_t fnp, void *argp) 1274 { 1275 #ifdef CAM_IOSCHED_DYNAMIC 1276 isc->latfcn = fnp; 1277 isc->latarg = argp; 1278 #endif 1279 } 1280 1281 /* 1282 * Client drivers can set two parameters. "goal" is the number of BIO_DELETEs 1283 * that will be queued up before iosched will "release" the trims to the client 1284 * driver to wo with what they will (usually combine as many as possible). If we 1285 * don't get this many, after trim_ticks we'll submit the I/O anyway with 1286 * whatever we have. We do need an I/O of some kind of to clock the deferred 1287 * trims out to disk. Since we will eventually get a write for the super block 1288 * or something before we shutdown, the trims will complete. To be safe, when a 1289 * BIO_FLUSH is presented to the iosched work queue, we set the ticks time far 1290 * enough in the past so we'll present the BIO_DELETEs to the client driver. 1291 * There might be a race if no BIO_DELETESs were queued, a BIO_FLUSH comes in 1292 * and then a BIO_DELETE is sent down. No know client does this, and there's 1293 * already a race between an ordered BIO_FLUSH and any BIO_DELETEs in flight, 1294 * but no client depends on the ordering being honored. 1295 * 1296 * XXX I'm not sure what the interaction between UFS direct BIOs and the BUF 1297 * flushing on shutdown. I think there's bufs that would be dependent on the BIO 1298 * finishing to write out at least metadata, so we'll be fine. To be safe, keep 1299 * the number of ticks low (less than maybe 10s) to avoid shutdown races. 1300 */ 1301 1302 void 1303 cam_iosched_set_trim_goal(struct cam_iosched_softc *isc, int goal) 1304 { 1305 1306 isc->trim_goal = goal; 1307 } 1308 1309 void 1310 cam_iosched_set_trim_ticks(struct cam_iosched_softc *isc, int trim_ticks) 1311 { 1312 1313 isc->trim_ticks = trim_ticks; 1314 } 1315 1316 /* 1317 * Flush outstanding I/O. Consumers of this library don't know all the 1318 * queues we may keep, so this allows all I/O to be flushed in one 1319 * convenient call. 1320 */ 1321 void 1322 cam_iosched_flush(struct cam_iosched_softc *isc, struct devstat *stp, int err) 1323 { 1324 bioq_flush(&isc->bio_queue, stp, err); 1325 bioq_flush(&isc->trim_queue, stp, err); 1326 #ifdef CAM_IOSCHED_DYNAMIC 1327 if (do_dynamic_iosched) 1328 bioq_flush(&isc->write_queue, stp, err); 1329 #endif 1330 } 1331 1332 #ifdef CAM_IOSCHED_DYNAMIC 1333 static struct bio * 1334 cam_iosched_get_write(struct cam_iosched_softc *isc) 1335 { 1336 struct bio *bp; 1337 1338 /* 1339 * We control the write rate by controlling how many requests we send 1340 * down to the drive at any one time. Fewer requests limits the 1341 * effects of both starvation when the requests take a while and write 1342 * amplification when each request is causing more than one write to 1343 * the NAND media. Limiting the queue depth like this will also limit 1344 * the write throughput and give and reads that want to compete to 1345 * compete unfairly. 1346 */ 1347 bp = bioq_first(&isc->write_queue); 1348 if (bp == NULL) { 1349 if (iosched_debug > 3) 1350 printf("No writes present in write_queue\n"); 1351 return NULL; 1352 } 1353 1354 /* 1355 * If pending read, prefer that based on current read bias 1356 * setting. 1357 */ 1358 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) { 1359 if (iosched_debug) 1360 printf( 1361 "Reads present and current_read_bias is %d queued " 1362 "writes %d queued reads %d\n", 1363 isc->current_read_bias, isc->write_stats.queued, 1364 isc->read_stats.queued); 1365 isc->current_read_bias--; 1366 /* We're not limiting writes, per se, just doing reads first */ 1367 return NULL; 1368 } 1369 1370 /* 1371 * See if our current limiter allows this I/O. 1372 */ 1373 if (cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) { 1374 if (iosched_debug) 1375 printf("Can't write because limiter says no.\n"); 1376 isc->write_stats.state_flags |= IOP_RATE_LIMITED; 1377 return NULL; 1378 } 1379 1380 /* 1381 * Let's do this: We've passed all the gates and we're a go 1382 * to schedule the I/O in the SIM. 1383 */ 1384 isc->current_read_bias = isc->read_bias; 1385 bioq_remove(&isc->write_queue, bp); 1386 if (bp->bio_cmd == BIO_WRITE) { 1387 isc->write_stats.queued--; 1388 isc->write_stats.total++; 1389 isc->write_stats.pending++; 1390 } 1391 if (iosched_debug > 9) 1392 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1393 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED; 1394 return bp; 1395 } 1396 #endif 1397 1398 /* 1399 * Put back a trim that you weren't able to actually schedule this time. 1400 */ 1401 void 1402 cam_iosched_put_back_trim(struct cam_iosched_softc *isc, struct bio *bp) 1403 { 1404 bioq_insert_head(&isc->trim_queue, bp); 1405 if (isc->queued_trims == 0) 1406 isc->last_trim_tick = ticks; 1407 isc->queued_trims++; 1408 #ifdef CAM_IOSCHED_DYNAMIC 1409 isc->trim_stats.queued++; 1410 isc->trim_stats.total--; /* since we put it back, don't double count */ 1411 isc->trim_stats.pending--; 1412 #endif 1413 } 1414 1415 /* 1416 * gets the next trim from the trim queue. 1417 * 1418 * Assumes we're called with the periph lock held. It removes this 1419 * trim from the queue and the device must explicitly reinsert it 1420 * should the need arise. 1421 */ 1422 struct bio * 1423 cam_iosched_next_trim(struct cam_iosched_softc *isc) 1424 { 1425 struct bio *bp; 1426 1427 bp = bioq_first(&isc->trim_queue); 1428 if (bp == NULL) 1429 return NULL; 1430 bioq_remove(&isc->trim_queue, bp); 1431 isc->queued_trims--; 1432 isc->last_trim_tick = ticks; /* Reset the tick timer when we take trims */ 1433 #ifdef CAM_IOSCHED_DYNAMIC 1434 isc->trim_stats.queued--; 1435 isc->trim_stats.total++; 1436 isc->trim_stats.pending++; 1437 #endif 1438 return bp; 1439 } 1440 1441 /* 1442 * gets an available trim from the trim queue, if there's no trim 1443 * already pending. It removes this trim from the queue and the device 1444 * must explicitly reinsert it should the need arise. 1445 * 1446 * Assumes we're called with the periph lock held. 1447 */ 1448 struct bio * 1449 cam_iosched_get_trim(struct cam_iosched_softc *isc) 1450 { 1451 #ifdef CAM_IOSCHED_DYNAMIC 1452 struct bio *bp; 1453 #endif 1454 1455 if (!cam_iosched_has_more_trim(isc)) 1456 return NULL; 1457 #ifdef CAM_IOSCHED_DYNAMIC 1458 bp = bioq_first(&isc->trim_queue); 1459 if (bp == NULL) 1460 return NULL; 1461 1462 /* 1463 * If pending read, prefer that based on current read bias setting. The 1464 * read bias is shared for both writes and TRIMs, but on TRIMs the bias 1465 * is for a combined TRIM not a single TRIM request that's come in. 1466 */ 1467 if (do_dynamic_iosched) { 1468 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) { 1469 if (iosched_debug) 1470 printf("Reads present and current_read_bias is %d" 1471 " queued trims %d queued reads %d\n", 1472 isc->current_read_bias, isc->trim_stats.queued, 1473 isc->read_stats.queued); 1474 isc->current_read_bias--; 1475 /* We're not limiting TRIMS, per se, just doing reads first */ 1476 return NULL; 1477 } 1478 /* 1479 * We're going to do a trim, so reset the bias. 1480 */ 1481 isc->current_read_bias = isc->read_bias; 1482 } 1483 1484 /* 1485 * See if our current limiter allows this I/O. Because we only call this 1486 * here, and not in next_trim, the 'bandwidth' limits for trims won't 1487 * work, while the iops or max queued limits will work. It's tricky 1488 * because we want the limits to be from the perspective of the 1489 * "commands sent to the device." To make iops work, we need to check 1490 * only here (since we want all the ops we combine to count as one). To 1491 * make bw limits work, we'd need to check in next_trim, but that would 1492 * have the effect of limiting the iops as seen from the upper layers. 1493 */ 1494 if (cam_iosched_limiter_iop(&isc->trim_stats, bp) != 0) { 1495 if (iosched_debug) 1496 printf("Can't trim because limiter says no.\n"); 1497 isc->trim_stats.state_flags |= IOP_RATE_LIMITED; 1498 return NULL; 1499 } 1500 isc->current_read_bias = isc->read_bias; 1501 isc->trim_stats.state_flags &= ~IOP_RATE_LIMITED; 1502 /* cam_iosched_next_trim below keeps proper book */ 1503 #endif 1504 return cam_iosched_next_trim(isc); 1505 } 1506 1507 1508 #ifdef CAM_IOSCHED_DYNAMIC 1509 static struct bio * 1510 bio_next(struct bio *bp) 1511 { 1512 bp = TAILQ_NEXT(bp, bio_queue); 1513 /* 1514 * After the first commands, the ordered bit terminates 1515 * our search because BIO_ORDERED acts like a barrier. 1516 */ 1517 if (bp == NULL || bp->bio_flags & BIO_ORDERED) 1518 return NULL; 1519 return bp; 1520 } 1521 1522 static bool 1523 cam_iosched_rate_limited(struct iop_stats *ios) 1524 { 1525 return ios->state_flags & IOP_RATE_LIMITED; 1526 } 1527 #endif 1528 1529 /* 1530 * Determine what the next bit of work to do is for the periph. The 1531 * default implementation looks to see if we have trims to do, but no 1532 * trims outstanding. If so, we do that. Otherwise we see if we have 1533 * other work. If we do, then we do that. Otherwise why were we called? 1534 */ 1535 struct bio * 1536 cam_iosched_next_bio(struct cam_iosched_softc *isc) 1537 { 1538 struct bio *bp; 1539 1540 /* 1541 * See if we have a trim that can be scheduled. We can only send one 1542 * at a time down, so this takes that into account. 1543 * 1544 * XXX newer TRIM commands are queueable. Revisit this when we 1545 * implement them. 1546 */ 1547 if ((bp = cam_iosched_get_trim(isc)) != NULL) 1548 return bp; 1549 1550 #ifdef CAM_IOSCHED_DYNAMIC 1551 /* 1552 * See if we have any pending writes, room in the queue for them, 1553 * and no pending reads (unless we've scheduled too many). 1554 * if so, those are next. 1555 */ 1556 if (do_dynamic_iosched) { 1557 if ((bp = cam_iosched_get_write(isc)) != NULL) 1558 return bp; 1559 } 1560 #endif 1561 /* 1562 * next, see if there's other, normal I/O waiting. If so return that. 1563 */ 1564 #ifdef CAM_IOSCHED_DYNAMIC 1565 if (do_dynamic_iosched) { 1566 for (bp = bioq_first(&isc->bio_queue); bp != NULL; 1567 bp = bio_next(bp)) { 1568 /* 1569 * For the dynamic scheduler with a read bias, bio_queue 1570 * is only for reads. However, without one, all 1571 * operations are queued. Enforce limits here for any 1572 * operation we find here. 1573 */ 1574 if (bp->bio_cmd == BIO_READ) { 1575 if (cam_iosched_rate_limited(&isc->read_stats) || 1576 cam_iosched_limiter_iop(&isc->read_stats, bp) != 0) { 1577 isc->read_stats.state_flags |= IOP_RATE_LIMITED; 1578 continue; 1579 } 1580 isc->read_stats.state_flags &= ~IOP_RATE_LIMITED; 1581 } 1582 /* 1583 * There can only be write requests on the queue when 1584 * the read bias is 0, but we need to process them 1585 * here. We do not assert for read bias == 0, however, 1586 * since it is dynamic and we can have WRITE operations 1587 * in the queue after we transition from 0 to non-zero. 1588 */ 1589 if (bp->bio_cmd == BIO_WRITE) { 1590 if (cam_iosched_rate_limited(&isc->write_stats) || 1591 cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) { 1592 isc->write_stats.state_flags |= IOP_RATE_LIMITED; 1593 continue; 1594 } 1595 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED; 1596 } 1597 /* 1598 * here we know we have a bp that's != NULL, that's not rate limited 1599 * and can be the next I/O. 1600 */ 1601 break; 1602 } 1603 } else 1604 #endif 1605 bp = bioq_first(&isc->bio_queue); 1606 1607 if (bp == NULL) 1608 return (NULL); 1609 bioq_remove(&isc->bio_queue, bp); 1610 #ifdef CAM_IOSCHED_DYNAMIC 1611 if (do_dynamic_iosched) { 1612 if (bp->bio_cmd == BIO_READ) { 1613 isc->read_stats.queued--; 1614 isc->read_stats.total++; 1615 isc->read_stats.pending++; 1616 } else if (bp->bio_cmd == BIO_WRITE) { 1617 isc->write_stats.queued--; 1618 isc->write_stats.total++; 1619 isc->write_stats.pending++; 1620 } 1621 } 1622 if (iosched_debug > 9) 1623 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1624 #endif 1625 return bp; 1626 } 1627 1628 /* 1629 * Driver has been given some work to do by the block layer. Tell the 1630 * scheduler about it and have it queue the work up. The scheduler module 1631 * will then return the currently most useful bit of work later, possibly 1632 * deferring work for various reasons. 1633 */ 1634 void 1635 cam_iosched_queue_work(struct cam_iosched_softc *isc, struct bio *bp) 1636 { 1637 1638 /* 1639 * A BIO_SPEEDUP from the uppper layers means that they have a block 1640 * shortage. At the present, this is only sent when we're trying to 1641 * allocate blocks, but have a shortage before giving up. bio_length is 1642 * the size of their shortage. We will complete just enough BIO_DELETEs 1643 * in the queue to satisfy the need. If bio_length is 0, we'll complete 1644 * them all. This allows the scheduler to delay BIO_DELETEs to improve 1645 * read/write performance without worrying about the upper layers. When 1646 * it's possibly a problem, we respond by pretending the BIO_DELETEs 1647 * just worked. We can't do anything about the BIO_DELETEs in the 1648 * hardware, though. We have to wait for them to complete. 1649 */ 1650 if (bp->bio_cmd == BIO_SPEEDUP) { 1651 off_t len; 1652 struct bio *nbp; 1653 1654 len = 0; 1655 while (bioq_first(&isc->trim_queue) && 1656 (bp->bio_length == 0 || len < bp->bio_length)) { 1657 nbp = bioq_takefirst(&isc->trim_queue); 1658 len += nbp->bio_length; 1659 nbp->bio_error = 0; 1660 biodone(nbp); 1661 } 1662 if (bp->bio_length > 0) { 1663 if (bp->bio_length > len) 1664 bp->bio_resid = bp->bio_length - len; 1665 else 1666 bp->bio_resid = 0; 1667 } 1668 bp->bio_error = 0; 1669 biodone(bp); 1670 return; 1671 } 1672 1673 /* 1674 * If we get a BIO_FLUSH, and we're doing delayed BIO_DELETEs then we 1675 * set the last tick time to one less than the current ticks minus the 1676 * delay to force the BIO_DELETEs to be presented to the client driver. 1677 */ 1678 if (bp->bio_cmd == BIO_FLUSH && isc->trim_ticks > 0) 1679 isc->last_trim_tick = ticks - isc->trim_ticks - 1; 1680 1681 /* 1682 * Put all trims on the trim queue. Otherwise put the work on the bio 1683 * queue. 1684 */ 1685 if (bp->bio_cmd == BIO_DELETE) { 1686 bioq_insert_tail(&isc->trim_queue, bp); 1687 if (isc->queued_trims == 0) 1688 isc->last_trim_tick = ticks; 1689 isc->queued_trims++; 1690 #ifdef CAM_IOSCHED_DYNAMIC 1691 isc->trim_stats.in++; 1692 isc->trim_stats.queued++; 1693 #endif 1694 } 1695 #ifdef CAM_IOSCHED_DYNAMIC 1696 else if (do_dynamic_iosched && isc->read_bias != 0 && 1697 (bp->bio_cmd != BIO_READ)) { 1698 if (cam_iosched_sort_queue(isc)) 1699 bioq_disksort(&isc->write_queue, bp); 1700 else 1701 bioq_insert_tail(&isc->write_queue, bp); 1702 if (iosched_debug > 9) 1703 printf("Qw : %p %#x\n", bp, bp->bio_cmd); 1704 if (bp->bio_cmd == BIO_WRITE) { 1705 isc->write_stats.in++; 1706 isc->write_stats.queued++; 1707 } 1708 } 1709 #endif 1710 else { 1711 if (cam_iosched_sort_queue(isc)) 1712 bioq_disksort(&isc->bio_queue, bp); 1713 else 1714 bioq_insert_tail(&isc->bio_queue, bp); 1715 #ifdef CAM_IOSCHED_DYNAMIC 1716 if (iosched_debug > 9) 1717 printf("Qr : %p %#x\n", bp, bp->bio_cmd); 1718 if (bp->bio_cmd == BIO_READ) { 1719 isc->read_stats.in++; 1720 isc->read_stats.queued++; 1721 } else if (bp->bio_cmd == BIO_WRITE) { 1722 isc->write_stats.in++; 1723 isc->write_stats.queued++; 1724 } 1725 #endif 1726 } 1727 } 1728 1729 /* 1730 * If we have work, get it scheduled. Called with the periph lock held. 1731 */ 1732 void 1733 cam_iosched_schedule(struct cam_iosched_softc *isc, struct cam_periph *periph) 1734 { 1735 1736 if (cam_iosched_has_work(isc)) 1737 xpt_schedule(periph, CAM_PRIORITY_NORMAL); 1738 } 1739 1740 /* 1741 * Complete a trim request. Mark that we no longer have one in flight. 1742 */ 1743 void 1744 cam_iosched_trim_done(struct cam_iosched_softc *isc) 1745 { 1746 1747 isc->flags &= ~CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1748 } 1749 1750 /* 1751 * Complete a bio. Called before we release the ccb with xpt_release_ccb so we 1752 * might use notes in the ccb for statistics. 1753 */ 1754 int 1755 cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp, 1756 union ccb *done_ccb) 1757 { 1758 int retval = 0; 1759 #ifdef CAM_IOSCHED_DYNAMIC 1760 if (!do_dynamic_iosched) 1761 return retval; 1762 1763 if (iosched_debug > 10) 1764 printf("done: %p %#x\n", bp, bp->bio_cmd); 1765 if (bp->bio_cmd == BIO_WRITE) { 1766 retval = cam_iosched_limiter_iodone(&isc->write_stats, bp); 1767 if ((bp->bio_flags & BIO_ERROR) != 0) 1768 isc->write_stats.errs++; 1769 isc->write_stats.out++; 1770 isc->write_stats.pending--; 1771 } else if (bp->bio_cmd == BIO_READ) { 1772 retval = cam_iosched_limiter_iodone(&isc->read_stats, bp); 1773 if ((bp->bio_flags & BIO_ERROR) != 0) 1774 isc->read_stats.errs++; 1775 isc->read_stats.out++; 1776 isc->read_stats.pending--; 1777 } else if (bp->bio_cmd == BIO_DELETE) { 1778 if ((bp->bio_flags & BIO_ERROR) != 0) 1779 isc->trim_stats.errs++; 1780 isc->trim_stats.out++; 1781 isc->trim_stats.pending--; 1782 } else if (bp->bio_cmd != BIO_FLUSH) { 1783 if (iosched_debug) 1784 printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd); 1785 } 1786 1787 if ((bp->bio_flags & BIO_ERROR) == 0 && done_ccb != NULL && 1788 (done_ccb->ccb_h.status & CAM_QOS_VALID) != 0) { 1789 sbintime_t sim_latency; 1790 1791 sim_latency = cam_iosched_sbintime_t(done_ccb->ccb_h.qos.periph_data); 1792 1793 cam_iosched_io_metric_update(isc, sim_latency, 1794 bp->bio_cmd, bp->bio_bcount); 1795 /* 1796 * Debugging code: allow callbacks to the periph driver when latency max 1797 * is exceeded. This can be useful for triggering external debugging actions. 1798 */ 1799 if (isc->latfcn && isc->max_lat != 0 && sim_latency > isc->max_lat) 1800 isc->latfcn(isc->latarg, sim_latency, bp); 1801 } 1802 1803 #endif 1804 return retval; 1805 } 1806 1807 /* 1808 * Tell the io scheduler that you've pushed a trim down into the sim. 1809 * This also tells the I/O scheduler not to push any more trims down, so 1810 * some periphs do not call it if they can cope with multiple trims in flight. 1811 */ 1812 void 1813 cam_iosched_submit_trim(struct cam_iosched_softc *isc) 1814 { 1815 1816 isc->flags |= CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1817 } 1818 1819 /* 1820 * Change the sorting policy hint for I/O transactions for this device. 1821 */ 1822 void 1823 cam_iosched_set_sort_queue(struct cam_iosched_softc *isc, int val) 1824 { 1825 1826 isc->sort_io_queue = val; 1827 } 1828 1829 int 1830 cam_iosched_has_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1831 { 1832 return isc->flags & flags; 1833 } 1834 1835 void 1836 cam_iosched_set_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1837 { 1838 isc->flags |= flags; 1839 } 1840 1841 void 1842 cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1843 { 1844 isc->flags &= ~flags; 1845 } 1846 1847 #ifdef CAM_IOSCHED_DYNAMIC 1848 /* 1849 * After the method presented in Jack Crenshaw's 1998 article "Integer 1850 * Square Roots," reprinted at 1851 * http://www.embedded.com/electronics-blogs/programmer-s-toolbox/4219659/Integer-Square-Roots 1852 * and well worth the read. Briefly, we find the power of 4 that's the 1853 * largest smaller than val. We then check each smaller power of 4 to 1854 * see if val is still bigger. The right shifts at each step divide 1855 * the result by 2 which after successive application winds up 1856 * accumulating the right answer. It could also have been accumulated 1857 * using a separate root counter, but this code is smaller and faster 1858 * than that method. This method is also integer size invariant. 1859 * It returns floor(sqrt((float)val)), or the largest integer less than 1860 * or equal to the square root. 1861 */ 1862 static uint64_t 1863 isqrt64(uint64_t val) 1864 { 1865 uint64_t res = 0; 1866 uint64_t bit = 1ULL << (sizeof(uint64_t) * NBBY - 2); 1867 1868 /* 1869 * Find the largest power of 4 smaller than val. 1870 */ 1871 while (bit > val) 1872 bit >>= 2; 1873 1874 /* 1875 * Accumulate the answer, one bit at a time (we keep moving 1876 * them over since 2 is the square root of 4 and we test 1877 * powers of 4). We accumulate where we find the bit, but 1878 * the successive shifts land the bit in the right place 1879 * by the end. 1880 */ 1881 while (bit != 0) { 1882 if (val >= res + bit) { 1883 val -= res + bit; 1884 res = (res >> 1) + bit; 1885 } else 1886 res >>= 1; 1887 bit >>= 2; 1888 } 1889 1890 return res; 1891 } 1892 1893 static sbintime_t latencies[LAT_BUCKETS - 1] = { 1894 BUCKET_BASE << 0, /* 20us */ 1895 BUCKET_BASE << 1, 1896 BUCKET_BASE << 2, 1897 BUCKET_BASE << 3, 1898 BUCKET_BASE << 4, 1899 BUCKET_BASE << 5, 1900 BUCKET_BASE << 6, 1901 BUCKET_BASE << 7, 1902 BUCKET_BASE << 8, 1903 BUCKET_BASE << 9, 1904 BUCKET_BASE << 10, 1905 BUCKET_BASE << 11, 1906 BUCKET_BASE << 12, 1907 BUCKET_BASE << 13, 1908 BUCKET_BASE << 14, 1909 BUCKET_BASE << 15, 1910 BUCKET_BASE << 16, 1911 BUCKET_BASE << 17, 1912 BUCKET_BASE << 18 /* 5,242,880us */ 1913 }; 1914 1915 static void 1916 cam_iosched_update(struct iop_stats *iop, sbintime_t sim_latency) 1917 { 1918 sbintime_t y, deltasq, delta; 1919 int i; 1920 1921 /* 1922 * Keep counts for latency. We do it by power of two buckets. 1923 * This helps us spot outlier behavior obscured by averages. 1924 */ 1925 for (i = 0; i < LAT_BUCKETS - 1; i++) { 1926 if (sim_latency < latencies[i]) { 1927 iop->latencies[i]++; 1928 break; 1929 } 1930 } 1931 if (i == LAT_BUCKETS - 1) 1932 iop->latencies[i]++; /* Put all > 8192ms values into the last bucket. */ 1933 1934 /* 1935 * Classic exponentially decaying average with a tiny alpha 1936 * (2 ^ -alpha_bits). For more info see the NIST statistical 1937 * handbook. 1938 * 1939 * ema_t = y_t * alpha + ema_t-1 * (1 - alpha) [nist] 1940 * ema_t = y_t * alpha + ema_t-1 - alpha * ema_t-1 1941 * ema_t = alpha * y_t - alpha * ema_t-1 + ema_t-1 1942 * alpha = 1 / (1 << alpha_bits) 1943 * sub e == ema_t-1, b == 1/alpha (== 1 << alpha_bits), d == y_t - ema_t-1 1944 * = y_t/b - e/b + be/b 1945 * = (y_t - e + be) / b 1946 * = (e + d) / b 1947 * 1948 * Since alpha is a power of two, we can compute this w/o any mult or 1949 * division. 1950 * 1951 * Variance can also be computed. Usually, it would be expressed as follows: 1952 * diff_t = y_t - ema_t-1 1953 * emvar_t = (1 - alpha) * (emavar_t-1 + diff_t^2 * alpha) 1954 * = emavar_t-1 - alpha * emavar_t-1 + delta_t^2 * alpha - (delta_t * alpha)^2 1955 * sub b == 1/alpha (== 1 << alpha_bits), e == emavar_t-1, d = delta_t^2 1956 * = e - e/b + dd/b + dd/bb 1957 * = (bbe - be + bdd + dd) / bb 1958 * = (bbe + b(dd-e) + dd) / bb (which is expanded below bb = 1<<(2*alpha_bits)) 1959 */ 1960 /* 1961 * XXX possible numeric issues 1962 * o We assume right shifted integers do the right thing, since that's 1963 * implementation defined. You can change the right shifts to / (1LL << alpha). 1964 * o alpha_bits = 9 gives ema ceiling of 23 bits of seconds for ema and 14 bits 1965 * for emvar. This puts a ceiling of 13 bits on alpha since we need a 1966 * few tens of seconds of representation. 1967 * o We mitigate alpha issues by never setting it too high. 1968 */ 1969 y = sim_latency; 1970 delta = (y - iop->ema); /* d */ 1971 iop->ema = ((iop->ema << alpha_bits) + delta) >> alpha_bits; 1972 1973 /* 1974 * Were we to naively plow ahead at this point, we wind up with many numerical 1975 * issues making any SD > ~3ms unreliable. So, we shift right by 12. This leaves 1976 * us with microsecond level precision in the input, so the same in the 1977 * output. It means we can't overflow deltasq unless delta > 4k seconds. It 1978 * also means that emvar can be up 46 bits 40 of which are fraction, which 1979 * gives us a way to measure up to ~8s in the SD before the computation goes 1980 * unstable. Even the worst hard disk rarely has > 1s service time in the 1981 * drive. It does mean we have to shift left 12 bits after taking the 1982 * square root to compute the actual standard deviation estimate. This loss of 1983 * precision is preferable to needing int128 types to work. The above numbers 1984 * assume alpha=9. 10 or 11 are ok, but we start to run into issues at 12, 1985 * so 12 or 13 is OK for EMA, EMVAR and SD will be wrong in those cases. 1986 */ 1987 delta >>= 12; 1988 deltasq = delta * delta; /* dd */ 1989 iop->emvar = ((iop->emvar << (2 * alpha_bits)) + /* bbe */ 1990 ((deltasq - iop->emvar) << alpha_bits) + /* b(dd-e) */ 1991 deltasq) /* dd */ 1992 >> (2 * alpha_bits); /* div bb */ 1993 iop->sd = (sbintime_t)isqrt64((uint64_t)iop->emvar) << 12; 1994 } 1995 1996 static void 1997 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 1998 sbintime_t sim_latency, int cmd, size_t size) 1999 { 2000 /* xxx Do we need to scale based on the size of the I/O ? */ 2001 switch (cmd) { 2002 case BIO_READ: 2003 cam_iosched_update(&isc->read_stats, sim_latency); 2004 break; 2005 case BIO_WRITE: 2006 cam_iosched_update(&isc->write_stats, sim_latency); 2007 break; 2008 case BIO_DELETE: 2009 cam_iosched_update(&isc->trim_stats, sim_latency); 2010 break; 2011 default: 2012 break; 2013 } 2014 } 2015 2016 #ifdef DDB 2017 static int biolen(struct bio_queue_head *bq) 2018 { 2019 int i = 0; 2020 struct bio *bp; 2021 2022 TAILQ_FOREACH(bp, &bq->queue, bio_queue) { 2023 i++; 2024 } 2025 return i; 2026 } 2027 2028 /* 2029 * Show the internal state of the I/O scheduler. 2030 */ 2031 DB_SHOW_COMMAND(iosched, cam_iosched_db_show) 2032 { 2033 struct cam_iosched_softc *isc; 2034 2035 if (!have_addr) { 2036 db_printf("Need addr\n"); 2037 return; 2038 } 2039 isc = (struct cam_iosched_softc *)addr; 2040 db_printf("pending_reads: %d\n", isc->read_stats.pending); 2041 db_printf("min_reads: %d\n", isc->read_stats.min); 2042 db_printf("max_reads: %d\n", isc->read_stats.max); 2043 db_printf("reads: %d\n", isc->read_stats.total); 2044 db_printf("in_reads: %d\n", isc->read_stats.in); 2045 db_printf("out_reads: %d\n", isc->read_stats.out); 2046 db_printf("queued_reads: %d\n", isc->read_stats.queued); 2047 db_printf("Read Q len %d\n", biolen(&isc->bio_queue)); 2048 db_printf("pending_writes: %d\n", isc->write_stats.pending); 2049 db_printf("min_writes: %d\n", isc->write_stats.min); 2050 db_printf("max_writes: %d\n", isc->write_stats.max); 2051 db_printf("writes: %d\n", isc->write_stats.total); 2052 db_printf("in_writes: %d\n", isc->write_stats.in); 2053 db_printf("out_writes: %d\n", isc->write_stats.out); 2054 db_printf("queued_writes: %d\n", isc->write_stats.queued); 2055 db_printf("Write Q len %d\n", biolen(&isc->write_queue)); 2056 db_printf("pending_trims: %d\n", isc->trim_stats.pending); 2057 db_printf("min_trims: %d\n", isc->trim_stats.min); 2058 db_printf("max_trims: %d\n", isc->trim_stats.max); 2059 db_printf("trims: %d\n", isc->trim_stats.total); 2060 db_printf("in_trims: %d\n", isc->trim_stats.in); 2061 db_printf("out_trims: %d\n", isc->trim_stats.out); 2062 db_printf("queued_trims: %d\n", isc->trim_stats.queued); 2063 db_printf("Trim Q len %d\n", biolen(&isc->trim_queue)); 2064 db_printf("read_bias: %d\n", isc->read_bias); 2065 db_printf("current_read_bias: %d\n", isc->current_read_bias); 2066 db_printf("Trim active? %s\n", 2067 (isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) ? "yes" : "no"); 2068 } 2069 #endif 2070 #endif 2071