1 /*- 2 * CAM IO Scheduler Interface 3 * 4 * SPDX-License-Identifier: BSD-2-Clause 5 * 6 * Copyright (c) 2015 Netflix, Inc. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 #include "opt_ddb.h" 31 32 #include <sys/param.h> 33 #include <sys/systm.h> 34 #include <sys/kernel.h> 35 #include <sys/bio.h> 36 #include <sys/lock.h> 37 #include <sys/malloc.h> 38 #include <sys/mutex.h> 39 #include <sys/sbuf.h> 40 #include <sys/sysctl.h> 41 42 #include <cam/cam.h> 43 #include <cam/cam_ccb.h> 44 #include <cam/cam_periph.h> 45 #include <cam/cam_xpt_periph.h> 46 #include <cam/cam_xpt_internal.h> 47 #include <cam/cam_iosched.h> 48 49 #include <ddb/ddb.h> 50 51 static MALLOC_DEFINE(M_CAMSCHED, "CAM I/O Scheduler", 52 "CAM I/O Scheduler buffers"); 53 54 static SYSCTL_NODE(_kern_cam, OID_AUTO, iosched, CTLFLAG_RD | CTLFLAG_MPSAFE, 0, 55 "CAM I/O Scheduler parameters"); 56 57 /* 58 * Default I/O scheduler for FreeBSD. This implementation is just a thin-vineer 59 * over the bioq_* interface, with notions of separate calls for normal I/O and 60 * for trims. 61 * 62 * When CAM_IOSCHED_DYNAMIC is defined, the scheduler is enhanced to dynamically 63 * steer the rate of one type of traffic to help other types of traffic (eg 64 * limit writes when read latency deteriorates on SSDs). 65 */ 66 67 #ifdef CAM_IOSCHED_DYNAMIC 68 69 static bool do_dynamic_iosched = true; 70 SYSCTL_BOOL(_kern_cam_iosched, OID_AUTO, dynamic, CTLFLAG_RDTUN, 71 &do_dynamic_iosched, 1, 72 "Enable Dynamic I/O scheduler optimizations."); 73 74 /* 75 * For an EMA, with an alpha of alpha, we know 76 * alpha = 2 / (N + 1) 77 * or 78 * N = 1 + (2 / alpha) 79 * where N is the number of samples that 86% of the current 80 * EMA is derived from. 81 * 82 * So we invent[*] alpha_bits: 83 * alpha_bits = -log_2(alpha) 84 * alpha = 2^-alpha_bits 85 * So 86 * N = 1 + 2^(alpha_bits + 1) 87 * 88 * The default 9 gives a 1025 lookback for 86% of the data. 89 * For a brief intro: https://en.wikipedia.org/wiki/Moving_average 90 * 91 * [*] Steal from the load average code and many other places. 92 * Note: See computation of EMA and EMVAR for acceptable ranges of alpha. 93 */ 94 static int alpha_bits = 9; 95 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, alpha_bits, CTLFLAG_RWTUN, 96 &alpha_bits, 1, 97 "Bits in EMA's alpha."); 98 99 /* 100 * Different parameters for the buckets of latency we keep track of. These are all 101 * published read-only since at present they are compile time constants. 102 * 103 * Bucket base is the upper bounds of the first latency bucket. It's currently 20us. 104 * With 20 buckets (see below), that leads to a geometric progression with a max size 105 * of 5.2s which is safeily larger than 1s to help diagnose extreme outliers better. 106 */ 107 #ifndef BUCKET_BASE 108 #define BUCKET_BASE ((SBT_1S / 50000) + 1) /* 20us */ 109 #endif 110 static sbintime_t bucket_base = BUCKET_BASE; 111 SYSCTL_SBINTIME_USEC(_kern_cam_iosched, OID_AUTO, bucket_base_us, CTLFLAG_RD, 112 &bucket_base, 113 "Size of the smallest latency bucket"); 114 115 /* 116 * Bucket ratio is the geometric progression for the bucket. For a bucket b_n 117 * the size of bucket b_n+1 is b_n * bucket_ratio / 100. 118 */ 119 static int bucket_ratio = 200; /* Rather hard coded at the moment */ 120 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, bucket_ratio, CTLFLAG_RD, 121 &bucket_ratio, 200, 122 "Latency Bucket Ratio for geometric progression."); 123 124 /* 125 * Number of total buckets. Starting at BUCKET_BASE, each one is a power of 2. 126 */ 127 #ifndef LAT_BUCKETS 128 #define LAT_BUCKETS 20 /* < 20us < 40us ... < 2^(n-1)*20us >= 2^(n-1)*20us */ 129 #endif 130 static int lat_buckets = LAT_BUCKETS; 131 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, buckets, CTLFLAG_RD, 132 &lat_buckets, LAT_BUCKETS, 133 "Total number of latency buckets published"); 134 135 /* 136 * Read bias: how many reads do we favor before scheduling a write 137 * when we have a choice. 138 */ 139 static int default_read_bias = 0; 140 SYSCTL_INT(_kern_cam_iosched, OID_AUTO, read_bias, CTLFLAG_RWTUN, 141 &default_read_bias, 0, 142 "Default read bias for new devices."); 143 144 struct iop_stats; 145 struct cam_iosched_softc; 146 147 int iosched_debug = 0; 148 149 typedef enum { 150 none = 0, /* No limits */ 151 queue_depth, /* Limit how many ops we queue to SIM */ 152 iops, /* Limit # of IOPS to the drive */ 153 bandwidth, /* Limit bandwidth to the drive */ 154 limiter_max 155 } io_limiter; 156 157 static const char *cam_iosched_limiter_names[] = 158 { "none", "queue_depth", "iops", "bandwidth" }; 159 160 /* 161 * Called to initialize the bits of the iop_stats structure relevant to the 162 * limiter. Called just after the limiter is set. 163 */ 164 typedef int l_init_t(struct iop_stats *); 165 166 /* 167 * Called every tick. 168 */ 169 typedef int l_tick_t(struct iop_stats *); 170 171 /* 172 * Called to see if the limiter thinks this IOP can be allowed to 173 * proceed. If so, the limiter assumes that the IOP proceeded 174 * and makes any accounting of it that's needed. 175 */ 176 typedef int l_iop_t(struct iop_stats *, struct bio *); 177 178 /* 179 * Called when an I/O completes so the limiter can update its 180 * accounting. Pending I/Os may complete in any order (even when 181 * sent to the hardware at the same time), so the limiter may not 182 * make any assumptions other than this I/O has completed. If it 183 * returns 1, then xpt_schedule() needs to be called again. 184 */ 185 typedef int l_iodone_t(struct iop_stats *, struct bio *); 186 187 static l_iop_t cam_iosched_qd_iop; 188 static l_iop_t cam_iosched_qd_caniop; 189 static l_iodone_t cam_iosched_qd_iodone; 190 191 static l_init_t cam_iosched_iops_init; 192 static l_tick_t cam_iosched_iops_tick; 193 static l_iop_t cam_iosched_iops_caniop; 194 static l_iop_t cam_iosched_iops_iop; 195 196 static l_init_t cam_iosched_bw_init; 197 static l_tick_t cam_iosched_bw_tick; 198 static l_iop_t cam_iosched_bw_caniop; 199 static l_iop_t cam_iosched_bw_iop; 200 201 struct limswitch { 202 l_init_t *l_init; 203 l_tick_t *l_tick; 204 l_iop_t *l_iop; 205 l_iop_t *l_caniop; 206 l_iodone_t *l_iodone; 207 } limsw[] = 208 { 209 { /* none */ 210 .l_init = NULL, 211 .l_tick = NULL, 212 .l_iop = NULL, 213 .l_iodone= NULL, 214 }, 215 { /* queue_depth */ 216 .l_init = NULL, 217 .l_tick = NULL, 218 .l_caniop = cam_iosched_qd_caniop, 219 .l_iop = cam_iosched_qd_iop, 220 .l_iodone= cam_iosched_qd_iodone, 221 }, 222 { /* iops */ 223 .l_init = cam_iosched_iops_init, 224 .l_tick = cam_iosched_iops_tick, 225 .l_caniop = cam_iosched_iops_caniop, 226 .l_iop = cam_iosched_iops_iop, 227 .l_iodone= NULL, 228 }, 229 { /* bandwidth */ 230 .l_init = cam_iosched_bw_init, 231 .l_tick = cam_iosched_bw_tick, 232 .l_caniop = cam_iosched_bw_caniop, 233 .l_iop = cam_iosched_bw_iop, 234 .l_iodone= NULL, 235 }, 236 }; 237 238 struct iop_stats { 239 /* 240 * sysctl state for this subnode. 241 */ 242 struct sysctl_ctx_list sysctl_ctx; 243 struct sysctl_oid *sysctl_tree; 244 245 /* 246 * Information about the current rate limiters, if any 247 */ 248 io_limiter limiter; /* How are I/Os being limited */ 249 int min; /* Low range of limit */ 250 int max; /* High range of limit */ 251 int current; /* Current rate limiter */ 252 int l_value1; /* per-limiter scratch value 1. */ 253 int l_value2; /* per-limiter scratch value 2. */ 254 255 /* 256 * Debug information about counts of I/Os that have gone through the 257 * scheduler. 258 */ 259 int pending; /* I/Os pending in the hardware */ 260 int queued; /* number currently in the queue */ 261 int total; /* Total for all time -- wraps */ 262 int in; /* number queued all time -- wraps */ 263 int out; /* number completed all time -- wraps */ 264 int errs; /* Number of I/Os completed with error -- wraps */ 265 266 /* 267 * Statistics on different bits of the process. 268 */ 269 /* Exp Moving Average, see alpha_bits for more details */ 270 sbintime_t ema; 271 sbintime_t emvar; 272 sbintime_t sd; /* Last computed sd */ 273 274 uint32_t state_flags; 275 #define IOP_RATE_LIMITED 1u 276 277 uint64_t latencies[LAT_BUCKETS]; 278 279 struct cam_iosched_softc *softc; 280 }; 281 282 typedef enum { 283 set_max = 0, /* current = max */ 284 read_latency, /* Steer read latency by throttling writes */ 285 cl_max /* Keep last */ 286 } control_type; 287 288 static const char *cam_iosched_control_type_names[] = 289 { "set_max", "read_latency" }; 290 291 struct control_loop { 292 /* 293 * sysctl state for this subnode. 294 */ 295 struct sysctl_ctx_list sysctl_ctx; 296 struct sysctl_oid *sysctl_tree; 297 298 sbintime_t next_steer; /* Time of next steer */ 299 sbintime_t steer_interval; /* How often do we steer? */ 300 sbintime_t lolat; 301 sbintime_t hilat; 302 int alpha; 303 control_type type; /* What type of control? */ 304 int last_count; /* Last I/O count */ 305 306 struct cam_iosched_softc *softc; 307 }; 308 309 #endif 310 311 struct cam_iosched_softc { 312 struct bio_queue_head bio_queue; 313 struct bio_queue_head trim_queue; 314 /* scheduler flags < 16, user flags >= 16 */ 315 uint32_t flags; 316 int sort_io_queue; 317 int trim_goal; /* # of trims to queue before sending */ 318 int trim_ticks; /* Max ticks to hold trims */ 319 int last_trim_tick; /* Last 'tick' time ld a trim */ 320 int queued_trims; /* Number of trims in the queue */ 321 #ifdef CAM_IOSCHED_DYNAMIC 322 int read_bias; /* Read bias setting */ 323 int current_read_bias; /* Current read bias state */ 324 int total_ticks; 325 int load; /* EMA of 'load average' of disk / 2^16 */ 326 327 struct bio_queue_head write_queue; 328 struct iop_stats read_stats, write_stats, trim_stats; 329 struct sysctl_ctx_list sysctl_ctx; 330 struct sysctl_oid *sysctl_tree; 331 332 int quanta; /* Number of quanta per second */ 333 struct callout ticker; /* Callout for our quota system */ 334 struct cam_periph *periph; /* cam periph associated with this device */ 335 uint32_t this_frac; /* Fraction of a second (1024ths) for this tick */ 336 sbintime_t last_time; /* Last time we ticked */ 337 struct control_loop cl; 338 sbintime_t max_lat; /* when != 0, if iop latency > max_lat, call max_lat_fcn */ 339 cam_iosched_latfcn_t latfcn; 340 void *latarg; 341 #endif 342 }; 343 344 #ifdef CAM_IOSCHED_DYNAMIC 345 /* 346 * helper functions to call the limsw functions. 347 */ 348 static int 349 cam_iosched_limiter_init(struct iop_stats *ios) 350 { 351 int lim = ios->limiter; 352 353 /* maybe this should be a kassert */ 354 if (lim < none || lim >= limiter_max) 355 return EINVAL; 356 357 if (limsw[lim].l_init) 358 return limsw[lim].l_init(ios); 359 360 return 0; 361 } 362 363 static int 364 cam_iosched_limiter_tick(struct iop_stats *ios) 365 { 366 int lim = ios->limiter; 367 368 /* maybe this should be a kassert */ 369 if (lim < none || lim >= limiter_max) 370 return EINVAL; 371 372 if (limsw[lim].l_tick) 373 return limsw[lim].l_tick(ios); 374 375 return 0; 376 } 377 378 static int 379 cam_iosched_limiter_iop(struct iop_stats *ios, struct bio *bp) 380 { 381 int lim = ios->limiter; 382 383 /* maybe this should be a kassert */ 384 if (lim < none || lim >= limiter_max) 385 return EINVAL; 386 387 if (limsw[lim].l_iop) 388 return limsw[lim].l_iop(ios, bp); 389 390 return 0; 391 } 392 393 static int 394 cam_iosched_limiter_caniop(struct iop_stats *ios, struct bio *bp) 395 { 396 int lim = ios->limiter; 397 398 /* maybe this should be a kassert */ 399 if (lim < none || lim >= limiter_max) 400 return EINVAL; 401 402 if (limsw[lim].l_caniop) 403 return limsw[lim].l_caniop(ios, bp); 404 405 return 0; 406 } 407 408 static int 409 cam_iosched_limiter_iodone(struct iop_stats *ios, struct bio *bp) 410 { 411 int lim = ios->limiter; 412 413 /* maybe this should be a kassert */ 414 if (lim < none || lim >= limiter_max) 415 return 0; 416 417 if (limsw[lim].l_iodone) 418 return limsw[lim].l_iodone(ios, bp); 419 420 return 0; 421 } 422 423 /* 424 * Functions to implement the different kinds of limiters 425 */ 426 427 static int 428 cam_iosched_qd_iop(struct iop_stats *ios, struct bio *bp) 429 { 430 431 if (ios->current <= 0 || ios->pending < ios->current) 432 return 0; 433 434 return EAGAIN; 435 } 436 437 static int 438 cam_iosched_qd_caniop(struct iop_stats *ios, struct bio *bp) 439 { 440 441 if (ios->current <= 0 || ios->pending < ios->current) 442 return 0; 443 444 return EAGAIN; 445 } 446 447 static int 448 cam_iosched_qd_iodone(struct iop_stats *ios, struct bio *bp) 449 { 450 451 if (ios->current <= 0 || ios->pending != ios->current) 452 return 0; 453 454 return 1; 455 } 456 457 static int 458 cam_iosched_iops_init(struct iop_stats *ios) 459 { 460 461 ios->l_value1 = ios->current / ios->softc->quanta; 462 if (ios->l_value1 <= 0) 463 ios->l_value1 = 1; 464 ios->l_value2 = 0; 465 466 return 0; 467 } 468 469 static int 470 cam_iosched_iops_tick(struct iop_stats *ios) 471 { 472 int new_ios; 473 474 /* 475 * Allow at least one IO per tick until all 476 * the IOs for this interval have been spent. 477 */ 478 new_ios = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16); 479 if (new_ios < 1 && ios->l_value2 < ios->current) { 480 new_ios = 1; 481 ios->l_value2++; 482 } 483 484 /* 485 * If this a new accounting interval, discard any "unspent" ios 486 * granted in the previous interval. Otherwise add the new ios to 487 * the previously granted ones that haven't been spent yet. 488 */ 489 if ((ios->softc->total_ticks % ios->softc->quanta) == 0) { 490 ios->l_value1 = new_ios; 491 ios->l_value2 = 1; 492 } else { 493 ios->l_value1 += new_ios; 494 } 495 496 return 0; 497 } 498 499 static int 500 cam_iosched_iops_caniop(struct iop_stats *ios, struct bio *bp) 501 { 502 503 /* 504 * So if we have any more IOPs left, allow it, 505 * otherwise wait. If current iops is 0, treat that 506 * as unlimited as a failsafe. 507 */ 508 if (ios->current > 0 && ios->l_value1 <= 0) 509 return EAGAIN; 510 return 0; 511 } 512 513 static int 514 cam_iosched_iops_iop(struct iop_stats *ios, struct bio *bp) 515 { 516 int rv; 517 518 rv = cam_iosched_limiter_caniop(ios, bp); 519 if (rv == 0) 520 ios->l_value1--; 521 522 return rv; 523 } 524 525 static int 526 cam_iosched_bw_init(struct iop_stats *ios) 527 { 528 529 /* ios->current is in kB/s, so scale to bytes */ 530 ios->l_value1 = ios->current * 1000 / ios->softc->quanta; 531 532 return 0; 533 } 534 535 static int 536 cam_iosched_bw_tick(struct iop_stats *ios) 537 { 538 int bw; 539 540 /* 541 * If we're in the hole for available quota from 542 * the last time, then add the quantum for this. 543 * If we have any left over from last quantum, 544 * then too bad, that's lost. Also, ios->current 545 * is in kB/s, so scale. 546 * 547 * We also allow up to 4 quanta of credits to 548 * accumulate to deal with burstiness. 4 is extremely 549 * arbitrary. 550 */ 551 bw = (int)((ios->current * 1000ull * (uint64_t)ios->softc->this_frac) >> 16); 552 if (ios->l_value1 < bw * 4) 553 ios->l_value1 += bw; 554 555 return 0; 556 } 557 558 static int 559 cam_iosched_bw_caniop(struct iop_stats *ios, struct bio *bp) 560 { 561 /* 562 * So if we have any more bw quota left, allow it, 563 * otherwise wait. Note, we'll go negative and that's 564 * OK. We'll just get a little less next quota. 565 * 566 * Note on going negative: that allows us to process 567 * requests in order better, since we won't allow 568 * shorter reads to get around the long one that we 569 * don't have the quota to do just yet. It also prevents 570 * starvation by being a little more permissive about 571 * what we let through this quantum (to prevent the 572 * starvation), at the cost of getting a little less 573 * next quantum. 574 * 575 * Also note that if the current limit is <= 0, 576 * we treat it as unlimited as a failsafe. 577 */ 578 if (ios->current > 0 && ios->l_value1 <= 0) 579 return EAGAIN; 580 581 return 0; 582 } 583 584 static int 585 cam_iosched_bw_iop(struct iop_stats *ios, struct bio *bp) 586 { 587 int rv; 588 589 rv = cam_iosched_limiter_caniop(ios, bp); 590 if (rv == 0) 591 ios->l_value1 -= bp->bio_length; 592 593 return rv; 594 } 595 596 static void cam_iosched_cl_maybe_steer(struct control_loop *clp); 597 598 static void 599 cam_iosched_ticker(void *arg) 600 { 601 struct cam_iosched_softc *isc = arg; 602 sbintime_t now, delta; 603 int pending; 604 605 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc); 606 607 now = sbinuptime(); 608 delta = now - isc->last_time; 609 isc->this_frac = (uint32_t)delta >> 16; /* Note: discards seconds -- should be 0 harmless if not */ 610 isc->last_time = now; 611 612 cam_iosched_cl_maybe_steer(&isc->cl); 613 614 cam_iosched_limiter_tick(&isc->read_stats); 615 cam_iosched_limiter_tick(&isc->write_stats); 616 cam_iosched_limiter_tick(&isc->trim_stats); 617 618 cam_iosched_schedule(isc, isc->periph); 619 620 /* 621 * isc->load is an EMA of the pending I/Os at each tick. The number of 622 * pending I/Os is the sum of the I/Os queued to the hardware, and those 623 * in the software queue that could be queued to the hardware if there 624 * were slots. 625 * 626 * ios_stats.pending is a count of requests in the SIM right now for 627 * each of these types of I/O. So the total pending count is the sum of 628 * these I/Os and the sum of the queued I/Os still in the software queue 629 * for those operations that aren't being rate limited at the moment. 630 * 631 * The reason for the rate limiting bit is because those I/Os 632 * aren't part of the software queued load (since we could 633 * give them to hardware, but choose not to). 634 * 635 * Note: due to a bug in counting pending TRIM in the device, we 636 * don't include them in this count. We count each BIO_DELETE in 637 * the pending count, but the periph drivers collapse them down 638 * into one TRIM command. That one trim command gets the completion 639 * so the counts get off. 640 */ 641 pending = isc->read_stats.pending + isc->write_stats.pending /* + isc->trim_stats.pending */; 642 pending += !!(isc->read_stats.state_flags & IOP_RATE_LIMITED) * isc->read_stats.queued + 643 !!(isc->write_stats.state_flags & IOP_RATE_LIMITED) * isc->write_stats.queued /* + 644 !!(isc->trim_stats.state_flags & IOP_RATE_LIMITED) * isc->trim_stats.queued */ ; 645 pending <<= 16; 646 pending /= isc->periph->path->device->ccbq.total_openings; 647 648 isc->load = (pending + (isc->load << 13) - isc->load) >> 13; /* see above: 13 -> 16139 / 200/s = ~81s ~1 minute */ 649 650 isc->total_ticks++; 651 } 652 653 static void 654 cam_iosched_cl_init(struct control_loop *clp, struct cam_iosched_softc *isc) 655 { 656 657 clp->next_steer = sbinuptime(); 658 clp->softc = isc; 659 clp->steer_interval = SBT_1S * 5; /* Let's start out steering every 5s */ 660 clp->lolat = 5 * SBT_1MS; 661 clp->hilat = 15 * SBT_1MS; 662 clp->alpha = 20; /* Alpha == gain. 20 = .2 */ 663 clp->type = set_max; 664 } 665 666 static void 667 cam_iosched_cl_maybe_steer(struct control_loop *clp) 668 { 669 struct cam_iosched_softc *isc; 670 sbintime_t now, lat; 671 int old; 672 673 isc = clp->softc; 674 now = isc->last_time; 675 if (now < clp->next_steer) 676 return; 677 678 clp->next_steer = now + clp->steer_interval; 679 switch (clp->type) { 680 case set_max: 681 if (isc->write_stats.current != isc->write_stats.max) 682 printf("Steering write from %d kBps to %d kBps\n", 683 isc->write_stats.current, isc->write_stats.max); 684 isc->read_stats.current = isc->read_stats.max; 685 isc->write_stats.current = isc->write_stats.max; 686 isc->trim_stats.current = isc->trim_stats.max; 687 break; 688 case read_latency: 689 old = isc->write_stats.current; 690 lat = isc->read_stats.ema; 691 /* 692 * Simple PLL-like engine. Since we're steering to a range for 693 * the SP (set point) that makes things a little more 694 * complicated. In addition, we're not directly controlling our 695 * PV (process variable), the read latency, but instead are 696 * manipulating the write bandwidth limit for our MV 697 * (manipulation variable), analysis of this code gets a bit 698 * messy. Also, the MV is a very noisy control surface for read 699 * latency since it is affected by many hidden processes inside 700 * the device which change how responsive read latency will be 701 * in reaction to changes in write bandwidth. Unlike the classic 702 * boiler control PLL. this may result in over-steering while 703 * the SSD takes its time to react to the new, lower load. This 704 * is why we use a relatively low alpha of between .1 and .25 to 705 * compensate for this effect. At .1, it takes ~22 steering 706 * intervals to back off by a factor of 10. At .2 it only takes 707 * ~10. At .25 it only takes ~8. However some preliminary data 708 * from the SSD drives suggests a reasponse time in 10's of 709 * seconds before latency drops regardless of the new write 710 * rate. Careful observation will be required to tune this 711 * effectively. 712 * 713 * Also, when there's no read traffic, we jack up the write 714 * limit too regardless of the last read latency. 10 is 715 * somewhat arbitrary. 716 */ 717 if (lat < clp->lolat || isc->read_stats.total - clp->last_count < 10) 718 isc->write_stats.current = isc->write_stats.current * 719 (100 + clp->alpha) / 100; /* Scale up */ 720 else if (lat > clp->hilat) 721 isc->write_stats.current = isc->write_stats.current * 722 (100 - clp->alpha) / 100; /* Scale down */ 723 clp->last_count = isc->read_stats.total; 724 725 /* 726 * Even if we don't steer, per se, enforce the min/max limits as 727 * those may have changed. 728 */ 729 if (isc->write_stats.current < isc->write_stats.min) 730 isc->write_stats.current = isc->write_stats.min; 731 if (isc->write_stats.current > isc->write_stats.max) 732 isc->write_stats.current = isc->write_stats.max; 733 if (old != isc->write_stats.current && iosched_debug) 734 printf("Steering write from %d kBps to %d kBps due to latency of %jdus\n", 735 old, isc->write_stats.current, 736 (uintmax_t)((uint64_t)1000000 * (uint32_t)lat) >> 32); 737 break; 738 case cl_max: 739 break; 740 } 741 } 742 #endif 743 744 /* 745 * Trim or similar currently pending completion. Should only be set for 746 * those drivers wishing only one Trim active at a time. 747 */ 748 #define CAM_IOSCHED_FLAG_TRIM_ACTIVE (1ul << 0) 749 /* Callout active, and needs to be torn down */ 750 #define CAM_IOSCHED_FLAG_CALLOUT_ACTIVE (1ul << 1) 751 752 /* Periph drivers set these flags to indicate work */ 753 #define CAM_IOSCHED_FLAG_WORK_FLAGS ((0xffffu) << 16) 754 755 #ifdef CAM_IOSCHED_DYNAMIC 756 static void 757 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 758 sbintime_t sim_latency, int cmd, size_t size); 759 #endif 760 761 static inline bool 762 cam_iosched_has_flagged_work(struct cam_iosched_softc *isc) 763 { 764 return !!(isc->flags & CAM_IOSCHED_FLAG_WORK_FLAGS); 765 } 766 767 static inline bool 768 cam_iosched_has_io(struct cam_iosched_softc *isc) 769 { 770 #ifdef CAM_IOSCHED_DYNAMIC 771 if (do_dynamic_iosched) { 772 struct bio *rbp = bioq_first(&isc->bio_queue); 773 struct bio *wbp = bioq_first(&isc->write_queue); 774 bool can_write = wbp != NULL && 775 cam_iosched_limiter_caniop(&isc->write_stats, wbp) == 0; 776 bool can_read = rbp != NULL && 777 cam_iosched_limiter_caniop(&isc->read_stats, rbp) == 0; 778 if (iosched_debug > 2) { 779 printf("can write %d: pending_writes %d max_writes %d\n", can_write, isc->write_stats.pending, isc->write_stats.max); 780 printf("can read %d: read_stats.pending %d max_reads %d\n", can_read, isc->read_stats.pending, isc->read_stats.max); 781 printf("Queued reads %d writes %d\n", isc->read_stats.queued, isc->write_stats.queued); 782 } 783 return can_read || can_write; 784 } 785 #endif 786 return bioq_first(&isc->bio_queue) != NULL; 787 } 788 789 static inline bool 790 cam_iosched_has_more_trim(struct cam_iosched_softc *isc) 791 { 792 struct bio *bp; 793 794 bp = bioq_first(&isc->trim_queue); 795 #ifdef CAM_IOSCHED_DYNAMIC 796 if (do_dynamic_iosched) { 797 /* 798 * If we're limiting trims, then defer action on trims 799 * for a bit. 800 */ 801 if (bp == NULL || cam_iosched_limiter_caniop(&isc->trim_stats, bp) != 0) 802 return false; 803 } 804 #endif 805 806 /* 807 * If we've set a trim_goal, then if we exceed that allow trims 808 * to be passed back to the driver. If we've also set a tick timeout 809 * allow trims back to the driver. Otherwise, don't allow trims yet. 810 */ 811 if (isc->trim_goal > 0) { 812 if (isc->queued_trims >= isc->trim_goal) 813 return true; 814 if (isc->queued_trims > 0 && 815 isc->trim_ticks > 0 && 816 ticks - isc->last_trim_tick > isc->trim_ticks) 817 return true; 818 return false; 819 } 820 821 /* NB: Should perhaps have a max trim active independent of I/O limiters */ 822 return !(isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) && bp != NULL; 823 } 824 825 #define cam_iosched_sort_queue(isc) ((isc)->sort_io_queue >= 0 ? \ 826 (isc)->sort_io_queue : cam_sort_io_queues) 827 828 static inline bool 829 cam_iosched_has_work(struct cam_iosched_softc *isc) 830 { 831 #ifdef CAM_IOSCHED_DYNAMIC 832 if (iosched_debug > 2) 833 printf("has work: %d %d %d\n", cam_iosched_has_io(isc), 834 cam_iosched_has_more_trim(isc), 835 cam_iosched_has_flagged_work(isc)); 836 #endif 837 838 return cam_iosched_has_io(isc) || 839 cam_iosched_has_more_trim(isc) || 840 cam_iosched_has_flagged_work(isc); 841 } 842 843 #ifdef CAM_IOSCHED_DYNAMIC 844 static void 845 cam_iosched_iop_stats_init(struct cam_iosched_softc *isc, struct iop_stats *ios) 846 { 847 848 ios->limiter = none; 849 ios->in = 0; 850 ios->max = ios->current = 300000; 851 ios->min = 1; 852 ios->out = 0; 853 ios->errs = 0; 854 ios->pending = 0; 855 ios->queued = 0; 856 ios->total = 0; 857 ios->ema = 0; 858 ios->emvar = 0; 859 ios->softc = isc; 860 cam_iosched_limiter_init(ios); 861 } 862 863 static int 864 cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS) 865 { 866 char buf[16]; 867 struct iop_stats *ios; 868 struct cam_iosched_softc *isc; 869 int value, i, error; 870 const char *p; 871 872 ios = arg1; 873 isc = ios->softc; 874 value = ios->limiter; 875 if (value < none || value >= limiter_max) 876 p = "UNKNOWN"; 877 else 878 p = cam_iosched_limiter_names[value]; 879 880 strlcpy(buf, p, sizeof(buf)); 881 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 882 if (error != 0 || req->newptr == NULL) 883 return error; 884 885 cam_periph_lock(isc->periph); 886 887 for (i = none; i < limiter_max; i++) { 888 if (strcmp(buf, cam_iosched_limiter_names[i]) != 0) 889 continue; 890 ios->limiter = i; 891 error = cam_iosched_limiter_init(ios); 892 if (error != 0) { 893 ios->limiter = value; 894 cam_periph_unlock(isc->periph); 895 return error; 896 } 897 /* Note: disk load averate requires ticker to be always running */ 898 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc); 899 isc->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 900 901 cam_periph_unlock(isc->periph); 902 return 0; 903 } 904 905 cam_periph_unlock(isc->periph); 906 return EINVAL; 907 } 908 909 static int 910 cam_iosched_control_type_sysctl(SYSCTL_HANDLER_ARGS) 911 { 912 char buf[16]; 913 struct control_loop *clp; 914 struct cam_iosched_softc *isc; 915 int value, i, error; 916 const char *p; 917 918 clp = arg1; 919 isc = clp->softc; 920 value = clp->type; 921 if (value < none || value >= cl_max) 922 p = "UNKNOWN"; 923 else 924 p = cam_iosched_control_type_names[value]; 925 926 strlcpy(buf, p, sizeof(buf)); 927 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 928 if (error != 0 || req->newptr == NULL) 929 return error; 930 931 for (i = set_max; i < cl_max; i++) { 932 if (strcmp(buf, cam_iosched_control_type_names[i]) != 0) 933 continue; 934 cam_periph_lock(isc->periph); 935 clp->type = i; 936 cam_periph_unlock(isc->periph); 937 return 0; 938 } 939 940 return EINVAL; 941 } 942 943 static int 944 cam_iosched_sbintime_sysctl(SYSCTL_HANDLER_ARGS) 945 { 946 char buf[16]; 947 sbintime_t value; 948 int error; 949 uint64_t us; 950 951 value = *(sbintime_t *)arg1; 952 us = (uint64_t)value / SBT_1US; 953 snprintf(buf, sizeof(buf), "%ju", (intmax_t)us); 954 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 955 if (error != 0 || req->newptr == NULL) 956 return error; 957 us = strtoul(buf, NULL, 10); 958 if (us == 0) 959 return EINVAL; 960 *(sbintime_t *)arg1 = us * SBT_1US; 961 return 0; 962 } 963 964 static int 965 cam_iosched_sysctl_latencies(SYSCTL_HANDLER_ARGS) 966 { 967 int i, error; 968 struct sbuf sb; 969 uint64_t *latencies; 970 971 latencies = arg1; 972 sbuf_new_for_sysctl(&sb, NULL, LAT_BUCKETS * 16, req); 973 974 for (i = 0; i < LAT_BUCKETS - 1; i++) 975 sbuf_printf(&sb, "%jd,", (intmax_t)latencies[i]); 976 sbuf_printf(&sb, "%jd", (intmax_t)latencies[LAT_BUCKETS - 1]); 977 error = sbuf_finish(&sb); 978 sbuf_delete(&sb); 979 980 return (error); 981 } 982 983 static int 984 cam_iosched_quanta_sysctl(SYSCTL_HANDLER_ARGS) 985 { 986 int *quanta; 987 int error, value; 988 989 quanta = (unsigned *)arg1; 990 value = *quanta; 991 992 error = sysctl_handle_int(oidp, (int *)&value, 0, req); 993 if ((error != 0) || (req->newptr == NULL)) 994 return (error); 995 996 if (value < 1 || value > hz) 997 return (EINVAL); 998 999 *quanta = value; 1000 1001 return (0); 1002 } 1003 1004 static void 1005 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct iop_stats *ios, char *name) 1006 { 1007 struct sysctl_oid_list *n; 1008 struct sysctl_ctx_list *ctx; 1009 1010 ios->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1011 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, name, 1012 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, name); 1013 n = SYSCTL_CHILDREN(ios->sysctl_tree); 1014 ctx = &ios->sysctl_ctx; 1015 1016 SYSCTL_ADD_UQUAD(ctx, n, 1017 OID_AUTO, "ema", CTLFLAG_RD, 1018 &ios->ema, 1019 "Fast Exponentially Weighted Moving Average"); 1020 SYSCTL_ADD_UQUAD(ctx, n, 1021 OID_AUTO, "emvar", CTLFLAG_RD, 1022 &ios->emvar, 1023 "Fast Exponentially Weighted Moving Variance"); 1024 1025 SYSCTL_ADD_INT(ctx, n, 1026 OID_AUTO, "pending", CTLFLAG_RD, 1027 &ios->pending, 0, 1028 "Instantaneous # of pending transactions"); 1029 SYSCTL_ADD_INT(ctx, n, 1030 OID_AUTO, "count", CTLFLAG_RD, 1031 &ios->total, 0, 1032 "# of transactions submitted to hardware"); 1033 SYSCTL_ADD_INT(ctx, n, 1034 OID_AUTO, "queued", CTLFLAG_RD, 1035 &ios->queued, 0, 1036 "# of transactions in the queue"); 1037 SYSCTL_ADD_INT(ctx, n, 1038 OID_AUTO, "in", CTLFLAG_RD, 1039 &ios->in, 0, 1040 "# of transactions queued to driver"); 1041 SYSCTL_ADD_INT(ctx, n, 1042 OID_AUTO, "out", CTLFLAG_RD, 1043 &ios->out, 0, 1044 "# of transactions completed (including with error)"); 1045 SYSCTL_ADD_INT(ctx, n, 1046 OID_AUTO, "errs", CTLFLAG_RD, 1047 &ios->errs, 0, 1048 "# of transactions completed with an error"); 1049 1050 SYSCTL_ADD_PROC(ctx, n, 1051 OID_AUTO, "limiter", 1052 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 1053 ios, 0, cam_iosched_limiter_sysctl, "A", 1054 "Current limiting type."); 1055 SYSCTL_ADD_INT(ctx, n, 1056 OID_AUTO, "min", CTLFLAG_RW, 1057 &ios->min, 0, 1058 "min resource"); 1059 SYSCTL_ADD_INT(ctx, n, 1060 OID_AUTO, "max", CTLFLAG_RW, 1061 &ios->max, 0, 1062 "max resource"); 1063 SYSCTL_ADD_INT(ctx, n, 1064 OID_AUTO, "current", CTLFLAG_RW, 1065 &ios->current, 0, 1066 "current resource"); 1067 1068 SYSCTL_ADD_PROC(ctx, n, 1069 OID_AUTO, "latencies", 1070 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, 1071 &ios->latencies, 0, 1072 cam_iosched_sysctl_latencies, "A", 1073 "Array of power of 2 latency from 1ms to 1.024s"); 1074 } 1075 1076 static void 1077 cam_iosched_iop_stats_fini(struct iop_stats *ios) 1078 { 1079 if (ios->sysctl_tree) 1080 if (sysctl_ctx_free(&ios->sysctl_ctx) != 0) 1081 printf("can't remove iosched sysctl stats context\n"); 1082 } 1083 1084 static void 1085 cam_iosched_cl_sysctl_init(struct cam_iosched_softc *isc) 1086 { 1087 struct sysctl_oid_list *n; 1088 struct sysctl_ctx_list *ctx; 1089 struct control_loop *clp; 1090 1091 clp = &isc->cl; 1092 clp->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1093 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, "control", 1094 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "Control loop info"); 1095 n = SYSCTL_CHILDREN(clp->sysctl_tree); 1096 ctx = &clp->sysctl_ctx; 1097 1098 SYSCTL_ADD_PROC(ctx, n, 1099 OID_AUTO, "type", 1100 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 1101 clp, 0, cam_iosched_control_type_sysctl, "A", 1102 "Control loop algorithm"); 1103 SYSCTL_ADD_PROC(ctx, n, 1104 OID_AUTO, "steer_interval", 1105 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 1106 &clp->steer_interval, 0, cam_iosched_sbintime_sysctl, "A", 1107 "How often to steer (in us)"); 1108 SYSCTL_ADD_PROC(ctx, n, 1109 OID_AUTO, "lolat", 1110 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 1111 &clp->lolat, 0, cam_iosched_sbintime_sysctl, "A", 1112 "Low water mark for Latency (in us)"); 1113 SYSCTL_ADD_PROC(ctx, n, 1114 OID_AUTO, "hilat", 1115 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, 1116 &clp->hilat, 0, cam_iosched_sbintime_sysctl, "A", 1117 "Hi water mark for Latency (in us)"); 1118 SYSCTL_ADD_INT(ctx, n, 1119 OID_AUTO, "alpha", CTLFLAG_RW, 1120 &clp->alpha, 0, 1121 "Alpha for PLL (x100) aka gain"); 1122 } 1123 1124 static void 1125 cam_iosched_cl_sysctl_fini(struct control_loop *clp) 1126 { 1127 if (clp->sysctl_tree) 1128 if (sysctl_ctx_free(&clp->sysctl_ctx) != 0) 1129 printf("can't remove iosched sysctl control loop context\n"); 1130 } 1131 #endif 1132 1133 /* 1134 * Allocate the iosched structure. This also insulates callers from knowing 1135 * sizeof struct cam_iosched_softc. 1136 */ 1137 int 1138 cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph) 1139 { 1140 1141 *iscp = malloc(sizeof(**iscp), M_CAMSCHED, M_NOWAIT | M_ZERO); 1142 if (*iscp == NULL) 1143 return ENOMEM; 1144 #ifdef CAM_IOSCHED_DYNAMIC 1145 if (iosched_debug) 1146 printf("CAM IOSCHEDULER Allocating entry at %p\n", *iscp); 1147 #endif 1148 (*iscp)->sort_io_queue = -1; 1149 bioq_init(&(*iscp)->bio_queue); 1150 bioq_init(&(*iscp)->trim_queue); 1151 #ifdef CAM_IOSCHED_DYNAMIC 1152 if (do_dynamic_iosched) { 1153 bioq_init(&(*iscp)->write_queue); 1154 (*iscp)->read_bias = default_read_bias; 1155 (*iscp)->current_read_bias = 0; 1156 (*iscp)->quanta = min(hz, 200); 1157 cam_iosched_iop_stats_init(*iscp, &(*iscp)->read_stats); 1158 cam_iosched_iop_stats_init(*iscp, &(*iscp)->write_stats); 1159 cam_iosched_iop_stats_init(*iscp, &(*iscp)->trim_stats); 1160 (*iscp)->trim_stats.max = 1; /* Trims are special: one at a time for now */ 1161 (*iscp)->last_time = sbinuptime(); 1162 callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0); 1163 (*iscp)->periph = periph; 1164 cam_iosched_cl_init(&(*iscp)->cl, *iscp); 1165 callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta, cam_iosched_ticker, *iscp); 1166 (*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1167 } 1168 #endif 1169 1170 return 0; 1171 } 1172 1173 /* 1174 * Reclaim all used resources. This assumes that other folks have 1175 * drained the requests in the hardware. Maybe an unwise assumption. 1176 */ 1177 void 1178 cam_iosched_fini(struct cam_iosched_softc *isc) 1179 { 1180 if (isc) { 1181 cam_iosched_flush(isc, NULL, ENXIO); 1182 #ifdef CAM_IOSCHED_DYNAMIC 1183 cam_iosched_iop_stats_fini(&isc->read_stats); 1184 cam_iosched_iop_stats_fini(&isc->write_stats); 1185 cam_iosched_iop_stats_fini(&isc->trim_stats); 1186 cam_iosched_cl_sysctl_fini(&isc->cl); 1187 if (isc->sysctl_tree) 1188 if (sysctl_ctx_free(&isc->sysctl_ctx) != 0) 1189 printf("can't remove iosched sysctl stats context\n"); 1190 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) { 1191 callout_drain(&isc->ticker); 1192 isc->flags &= ~ CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1193 } 1194 #endif 1195 free(isc, M_CAMSCHED); 1196 } 1197 } 1198 1199 /* 1200 * After we're sure we're attaching a device, go ahead and add 1201 * hooks for any sysctl we may wish to honor. 1202 */ 1203 void cam_iosched_sysctl_init(struct cam_iosched_softc *isc, 1204 struct sysctl_ctx_list *ctx, struct sysctl_oid *node) 1205 { 1206 struct sysctl_oid_list *n; 1207 1208 n = SYSCTL_CHILDREN(node); 1209 SYSCTL_ADD_INT(ctx, n, 1210 OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE, 1211 &isc->sort_io_queue, 0, 1212 "Sort IO queue to try and optimise disk access patterns"); 1213 SYSCTL_ADD_INT(ctx, n, 1214 OID_AUTO, "trim_goal", CTLFLAG_RW, 1215 &isc->trim_goal, 0, 1216 "Number of trims to try to accumulate before sending to hardware"); 1217 SYSCTL_ADD_INT(ctx, n, 1218 OID_AUTO, "trim_ticks", CTLFLAG_RW, 1219 &isc->trim_goal, 0, 1220 "IO Schedul qaunta to hold back trims for when accumulating"); 1221 1222 #ifdef CAM_IOSCHED_DYNAMIC 1223 if (!do_dynamic_iosched) 1224 return; 1225 1226 isc->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1227 SYSCTL_CHILDREN(node), OID_AUTO, "iosched", 1228 CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "I/O scheduler statistics"); 1229 n = SYSCTL_CHILDREN(isc->sysctl_tree); 1230 ctx = &isc->sysctl_ctx; 1231 1232 cam_iosched_iop_stats_sysctl_init(isc, &isc->read_stats, "read"); 1233 cam_iosched_iop_stats_sysctl_init(isc, &isc->write_stats, "write"); 1234 cam_iosched_iop_stats_sysctl_init(isc, &isc->trim_stats, "trim"); 1235 cam_iosched_cl_sysctl_init(isc); 1236 1237 SYSCTL_ADD_INT(ctx, n, 1238 OID_AUTO, "read_bias", CTLFLAG_RW, 1239 &isc->read_bias, default_read_bias, 1240 "How biased towards read should we be independent of limits"); 1241 1242 SYSCTL_ADD_PROC(ctx, n, 1243 OID_AUTO, "quanta", CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 1244 &isc->quanta, 0, cam_iosched_quanta_sysctl, "I", 1245 "How many quanta per second do we slice the I/O up into"); 1246 1247 SYSCTL_ADD_INT(ctx, n, 1248 OID_AUTO, "total_ticks", CTLFLAG_RD, 1249 &isc->total_ticks, 0, 1250 "Total number of ticks we've done"); 1251 1252 SYSCTL_ADD_INT(ctx, n, 1253 OID_AUTO, "load", CTLFLAG_RD, 1254 &isc->load, 0, 1255 "scaled load average / 100"); 1256 1257 SYSCTL_ADD_U64(ctx, n, 1258 OID_AUTO, "latency_trigger", CTLFLAG_RW, 1259 &isc->max_lat, 0, 1260 "Latency treshold to trigger callbacks"); 1261 #endif 1262 } 1263 1264 void 1265 cam_iosched_set_latfcn(struct cam_iosched_softc *isc, 1266 cam_iosched_latfcn_t fnp, void *argp) 1267 { 1268 #ifdef CAM_IOSCHED_DYNAMIC 1269 isc->latfcn = fnp; 1270 isc->latarg = argp; 1271 #endif 1272 } 1273 1274 /* 1275 * Client drivers can set two parameters. "goal" is the number of BIO_DELETEs 1276 * that will be queued up before iosched will "release" the trims to the client 1277 * driver to wo with what they will (usually combine as many as possible). If we 1278 * don't get this many, after trim_ticks we'll submit the I/O anyway with 1279 * whatever we have. We do need an I/O of some kind of to clock the deferred 1280 * trims out to disk. Since we will eventually get a write for the super block 1281 * or something before we shutdown, the trims will complete. To be safe, when a 1282 * BIO_FLUSH is presented to the iosched work queue, we set the ticks time far 1283 * enough in the past so we'll present the BIO_DELETEs to the client driver. 1284 * There might be a race if no BIO_DELETESs were queued, a BIO_FLUSH comes in 1285 * and then a BIO_DELETE is sent down. No know client does this, and there's 1286 * already a race between an ordered BIO_FLUSH and any BIO_DELETEs in flight, 1287 * but no client depends on the ordering being honored. 1288 * 1289 * XXX I'm not sure what the interaction between UFS direct BIOs and the BUF 1290 * flushing on shutdown. I think there's bufs that would be dependent on the BIO 1291 * finishing to write out at least metadata, so we'll be fine. To be safe, keep 1292 * the number of ticks low (less than maybe 10s) to avoid shutdown races. 1293 */ 1294 1295 void 1296 cam_iosched_set_trim_goal(struct cam_iosched_softc *isc, int goal) 1297 { 1298 1299 isc->trim_goal = goal; 1300 } 1301 1302 void 1303 cam_iosched_set_trim_ticks(struct cam_iosched_softc *isc, int trim_ticks) 1304 { 1305 1306 isc->trim_ticks = trim_ticks; 1307 } 1308 1309 /* 1310 * Flush outstanding I/O. Consumers of this library don't know all the 1311 * queues we may keep, so this allows all I/O to be flushed in one 1312 * convenient call. 1313 */ 1314 void 1315 cam_iosched_flush(struct cam_iosched_softc *isc, struct devstat *stp, int err) 1316 { 1317 bioq_flush(&isc->bio_queue, stp, err); 1318 bioq_flush(&isc->trim_queue, stp, err); 1319 #ifdef CAM_IOSCHED_DYNAMIC 1320 if (do_dynamic_iosched) 1321 bioq_flush(&isc->write_queue, stp, err); 1322 #endif 1323 } 1324 1325 #ifdef CAM_IOSCHED_DYNAMIC 1326 static struct bio * 1327 cam_iosched_get_write(struct cam_iosched_softc *isc) 1328 { 1329 struct bio *bp; 1330 1331 /* 1332 * We control the write rate by controlling how many requests we send 1333 * down to the drive at any one time. Fewer requests limits the 1334 * effects of both starvation when the requests take a while and write 1335 * amplification when each request is causing more than one write to 1336 * the NAND media. Limiting the queue depth like this will also limit 1337 * the write throughput and give and reads that want to compete to 1338 * compete unfairly. 1339 */ 1340 bp = bioq_first(&isc->write_queue); 1341 if (bp == NULL) { 1342 if (iosched_debug > 3) 1343 printf("No writes present in write_queue\n"); 1344 return NULL; 1345 } 1346 1347 /* 1348 * If pending read, prefer that based on current read bias 1349 * setting. 1350 */ 1351 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) { 1352 if (iosched_debug) 1353 printf( 1354 "Reads present and current_read_bias is %d queued " 1355 "writes %d queued reads %d\n", 1356 isc->current_read_bias, isc->write_stats.queued, 1357 isc->read_stats.queued); 1358 isc->current_read_bias--; 1359 /* We're not limiting writes, per se, just doing reads first */ 1360 return NULL; 1361 } 1362 1363 /* 1364 * See if our current limiter allows this I/O. 1365 */ 1366 if (cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) { 1367 if (iosched_debug) 1368 printf("Can't write because limiter says no.\n"); 1369 isc->write_stats.state_flags |= IOP_RATE_LIMITED; 1370 return NULL; 1371 } 1372 1373 /* 1374 * Let's do this: We've passed all the gates and we're a go 1375 * to schedule the I/O in the SIM. 1376 */ 1377 isc->current_read_bias = isc->read_bias; 1378 bioq_remove(&isc->write_queue, bp); 1379 if (bp->bio_cmd == BIO_WRITE) { 1380 isc->write_stats.queued--; 1381 isc->write_stats.total++; 1382 isc->write_stats.pending++; 1383 } 1384 if (iosched_debug > 9) 1385 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1386 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED; 1387 return bp; 1388 } 1389 #endif 1390 1391 /* 1392 * Put back a trim that you weren't able to actually schedule this time. 1393 */ 1394 void 1395 cam_iosched_put_back_trim(struct cam_iosched_softc *isc, struct bio *bp) 1396 { 1397 bioq_insert_head(&isc->trim_queue, bp); 1398 if (isc->queued_trims == 0) 1399 isc->last_trim_tick = ticks; 1400 isc->queued_trims++; 1401 #ifdef CAM_IOSCHED_DYNAMIC 1402 isc->trim_stats.queued++; 1403 isc->trim_stats.total--; /* since we put it back, don't double count */ 1404 isc->trim_stats.pending--; 1405 #endif 1406 } 1407 1408 /* 1409 * gets the next trim from the trim queue. 1410 * 1411 * Assumes we're called with the periph lock held. It removes this 1412 * trim from the queue and the device must explicitly reinsert it 1413 * should the need arise. 1414 */ 1415 struct bio * 1416 cam_iosched_next_trim(struct cam_iosched_softc *isc) 1417 { 1418 struct bio *bp; 1419 1420 bp = bioq_first(&isc->trim_queue); 1421 if (bp == NULL) 1422 return NULL; 1423 bioq_remove(&isc->trim_queue, bp); 1424 isc->queued_trims--; 1425 isc->last_trim_tick = ticks; /* Reset the tick timer when we take trims */ 1426 #ifdef CAM_IOSCHED_DYNAMIC 1427 isc->trim_stats.queued--; 1428 isc->trim_stats.total++; 1429 isc->trim_stats.pending++; 1430 #endif 1431 return bp; 1432 } 1433 1434 /* 1435 * gets an available trim from the trim queue, if there's no trim 1436 * already pending. It removes this trim from the queue and the device 1437 * must explicitly reinsert it should the need arise. 1438 * 1439 * Assumes we're called with the periph lock held. 1440 */ 1441 struct bio * 1442 cam_iosched_get_trim(struct cam_iosched_softc *isc) 1443 { 1444 #ifdef CAM_IOSCHED_DYNAMIC 1445 struct bio *bp; 1446 #endif 1447 1448 if (!cam_iosched_has_more_trim(isc)) 1449 return NULL; 1450 #ifdef CAM_IOSCHED_DYNAMIC 1451 bp = bioq_first(&isc->trim_queue); 1452 if (bp == NULL) 1453 return NULL; 1454 1455 /* 1456 * If pending read, prefer that based on current read bias setting. The 1457 * read bias is shared for both writes and TRIMs, but on TRIMs the bias 1458 * is for a combined TRIM not a single TRIM request that's come in. 1459 */ 1460 if (do_dynamic_iosched) { 1461 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) { 1462 if (iosched_debug) 1463 printf("Reads present and current_read_bias is %d" 1464 " queued trims %d queued reads %d\n", 1465 isc->current_read_bias, isc->trim_stats.queued, 1466 isc->read_stats.queued); 1467 isc->current_read_bias--; 1468 /* We're not limiting TRIMS, per se, just doing reads first */ 1469 return NULL; 1470 } 1471 /* 1472 * We're going to do a trim, so reset the bias. 1473 */ 1474 isc->current_read_bias = isc->read_bias; 1475 } 1476 1477 /* 1478 * See if our current limiter allows this I/O. Because we only call this 1479 * here, and not in next_trim, the 'bandwidth' limits for trims won't 1480 * work, while the iops or max queued limits will work. It's tricky 1481 * because we want the limits to be from the perspective of the 1482 * "commands sent to the device." To make iops work, we need to check 1483 * only here (since we want all the ops we combine to count as one). To 1484 * make bw limits work, we'd need to check in next_trim, but that would 1485 * have the effect of limiting the iops as seen from the upper layers. 1486 */ 1487 if (cam_iosched_limiter_iop(&isc->trim_stats, bp) != 0) { 1488 if (iosched_debug) 1489 printf("Can't trim because limiter says no.\n"); 1490 isc->trim_stats.state_flags |= IOP_RATE_LIMITED; 1491 return NULL; 1492 } 1493 isc->current_read_bias = isc->read_bias; 1494 isc->trim_stats.state_flags &= ~IOP_RATE_LIMITED; 1495 /* cam_iosched_next_trim below keeps proper book */ 1496 #endif 1497 return cam_iosched_next_trim(isc); 1498 } 1499 1500 1501 #ifdef CAM_IOSCHED_DYNAMIC 1502 static struct bio * 1503 bio_next(struct bio *bp) 1504 { 1505 bp = TAILQ_NEXT(bp, bio_queue); 1506 /* 1507 * After the first commands, the ordered bit terminates 1508 * our search because BIO_ORDERED acts like a barrier. 1509 */ 1510 if (bp == NULL || bp->bio_flags & BIO_ORDERED) 1511 return NULL; 1512 return bp; 1513 } 1514 1515 static bool 1516 cam_iosched_rate_limited(struct iop_stats *ios) 1517 { 1518 return ios->state_flags & IOP_RATE_LIMITED; 1519 } 1520 #endif 1521 1522 /* 1523 * Determine what the next bit of work to do is for the periph. The 1524 * default implementation looks to see if we have trims to do, but no 1525 * trims outstanding. If so, we do that. Otherwise we see if we have 1526 * other work. If we do, then we do that. Otherwise why were we called? 1527 */ 1528 struct bio * 1529 cam_iosched_next_bio(struct cam_iosched_softc *isc) 1530 { 1531 struct bio *bp; 1532 1533 /* 1534 * See if we have a trim that can be scheduled. We can only send one 1535 * at a time down, so this takes that into account. 1536 * 1537 * XXX newer TRIM commands are queueable. Revisit this when we 1538 * implement them. 1539 */ 1540 if ((bp = cam_iosched_get_trim(isc)) != NULL) 1541 return bp; 1542 1543 #ifdef CAM_IOSCHED_DYNAMIC 1544 /* 1545 * See if we have any pending writes, room in the queue for them, 1546 * and no pending reads (unless we've scheduled too many). 1547 * if so, those are next. 1548 */ 1549 if (do_dynamic_iosched) { 1550 if ((bp = cam_iosched_get_write(isc)) != NULL) 1551 return bp; 1552 } 1553 #endif 1554 /* 1555 * next, see if there's other, normal I/O waiting. If so return that. 1556 */ 1557 #ifdef CAM_IOSCHED_DYNAMIC 1558 if (do_dynamic_iosched) { 1559 for (bp = bioq_first(&isc->bio_queue); bp != NULL; 1560 bp = bio_next(bp)) { 1561 /* 1562 * For the dynamic scheduler with a read bias, bio_queue 1563 * is only for reads. However, without one, all 1564 * operations are queued. Enforce limits here for any 1565 * operation we find here. 1566 */ 1567 if (bp->bio_cmd == BIO_READ) { 1568 if (cam_iosched_rate_limited(&isc->read_stats) || 1569 cam_iosched_limiter_iop(&isc->read_stats, bp) != 0) { 1570 isc->read_stats.state_flags |= IOP_RATE_LIMITED; 1571 continue; 1572 } 1573 isc->read_stats.state_flags &= ~IOP_RATE_LIMITED; 1574 } 1575 /* 1576 * There can only be write requests on the queue when 1577 * the read bias is 0, but we need to process them 1578 * here. We do not assert for read bias == 0, however, 1579 * since it is dynamic and we can have WRITE operations 1580 * in the queue after we transition from 0 to non-zero. 1581 */ 1582 if (bp->bio_cmd == BIO_WRITE) { 1583 if (cam_iosched_rate_limited(&isc->write_stats) || 1584 cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) { 1585 isc->write_stats.state_flags |= IOP_RATE_LIMITED; 1586 continue; 1587 } 1588 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED; 1589 } 1590 /* 1591 * here we know we have a bp that's != NULL, that's not rate limited 1592 * and can be the next I/O. 1593 */ 1594 break; 1595 } 1596 } else 1597 #endif 1598 bp = bioq_first(&isc->bio_queue); 1599 1600 if (bp == NULL) 1601 return (NULL); 1602 bioq_remove(&isc->bio_queue, bp); 1603 #ifdef CAM_IOSCHED_DYNAMIC 1604 if (do_dynamic_iosched) { 1605 if (bp->bio_cmd == BIO_READ) { 1606 isc->read_stats.queued--; 1607 isc->read_stats.total++; 1608 isc->read_stats.pending++; 1609 } else if (bp->bio_cmd == BIO_WRITE) { 1610 isc->write_stats.queued--; 1611 isc->write_stats.total++; 1612 isc->write_stats.pending++; 1613 } 1614 } 1615 if (iosched_debug > 9) 1616 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1617 #endif 1618 return bp; 1619 } 1620 1621 /* 1622 * Driver has been given some work to do by the block layer. Tell the 1623 * scheduler about it and have it queue the work up. The scheduler module 1624 * will then return the currently most useful bit of work later, possibly 1625 * deferring work for various reasons. 1626 */ 1627 void 1628 cam_iosched_queue_work(struct cam_iosched_softc *isc, struct bio *bp) 1629 { 1630 1631 /* 1632 * A BIO_SPEEDUP from the upper layers means that they have a block 1633 * shortage. At the present, this is only sent when we're trying to 1634 * allocate blocks, but have a shortage before giving up. bio_length is 1635 * the size of their shortage. We will complete just enough BIO_DELETEs 1636 * in the queue to satisfy the need. If bio_length is 0, we'll complete 1637 * them all. This allows the scheduler to delay BIO_DELETEs to improve 1638 * read/write performance without worrying about the upper layers. When 1639 * it's possibly a problem, we respond by pretending the BIO_DELETEs 1640 * just worked. We can't do anything about the BIO_DELETEs in the 1641 * hardware, though. We have to wait for them to complete. 1642 */ 1643 if (bp->bio_cmd == BIO_SPEEDUP) { 1644 off_t len; 1645 struct bio *nbp; 1646 1647 len = 0; 1648 while (bioq_first(&isc->trim_queue) && 1649 (bp->bio_length == 0 || len < bp->bio_length)) { 1650 nbp = bioq_takefirst(&isc->trim_queue); 1651 len += nbp->bio_length; 1652 nbp->bio_error = 0; 1653 biodone(nbp); 1654 } 1655 if (bp->bio_length > 0) { 1656 if (bp->bio_length > len) 1657 bp->bio_resid = bp->bio_length - len; 1658 else 1659 bp->bio_resid = 0; 1660 } 1661 bp->bio_error = 0; 1662 biodone(bp); 1663 return; 1664 } 1665 1666 /* 1667 * If we get a BIO_FLUSH, and we're doing delayed BIO_DELETEs then we 1668 * set the last tick time to one less than the current ticks minus the 1669 * delay to force the BIO_DELETEs to be presented to the client driver. 1670 */ 1671 if (bp->bio_cmd == BIO_FLUSH && isc->trim_ticks > 0) 1672 isc->last_trim_tick = ticks - isc->trim_ticks - 1; 1673 1674 /* 1675 * Put all trims on the trim queue. Otherwise put the work on the bio 1676 * queue. 1677 */ 1678 if (bp->bio_cmd == BIO_DELETE) { 1679 bioq_insert_tail(&isc->trim_queue, bp); 1680 if (isc->queued_trims == 0) 1681 isc->last_trim_tick = ticks; 1682 isc->queued_trims++; 1683 #ifdef CAM_IOSCHED_DYNAMIC 1684 isc->trim_stats.in++; 1685 isc->trim_stats.queued++; 1686 #endif 1687 } 1688 #ifdef CAM_IOSCHED_DYNAMIC 1689 else if (do_dynamic_iosched && isc->read_bias != 0 && 1690 (bp->bio_cmd != BIO_READ)) { 1691 if (cam_iosched_sort_queue(isc)) 1692 bioq_disksort(&isc->write_queue, bp); 1693 else 1694 bioq_insert_tail(&isc->write_queue, bp); 1695 if (iosched_debug > 9) 1696 printf("Qw : %p %#x\n", bp, bp->bio_cmd); 1697 if (bp->bio_cmd == BIO_WRITE) { 1698 isc->write_stats.in++; 1699 isc->write_stats.queued++; 1700 } 1701 } 1702 #endif 1703 else { 1704 if (cam_iosched_sort_queue(isc)) 1705 bioq_disksort(&isc->bio_queue, bp); 1706 else 1707 bioq_insert_tail(&isc->bio_queue, bp); 1708 #ifdef CAM_IOSCHED_DYNAMIC 1709 if (iosched_debug > 9) 1710 printf("Qr : %p %#x\n", bp, bp->bio_cmd); 1711 if (bp->bio_cmd == BIO_READ) { 1712 isc->read_stats.in++; 1713 isc->read_stats.queued++; 1714 } else if (bp->bio_cmd == BIO_WRITE) { 1715 isc->write_stats.in++; 1716 isc->write_stats.queued++; 1717 } 1718 #endif 1719 } 1720 } 1721 1722 /* 1723 * If we have work, get it scheduled. Called with the periph lock held. 1724 */ 1725 void 1726 cam_iosched_schedule(struct cam_iosched_softc *isc, struct cam_periph *periph) 1727 { 1728 1729 if (cam_iosched_has_work(isc)) 1730 xpt_schedule(periph, CAM_PRIORITY_NORMAL); 1731 } 1732 1733 /* 1734 * Complete a trim request. Mark that we no longer have one in flight. 1735 */ 1736 void 1737 cam_iosched_trim_done(struct cam_iosched_softc *isc) 1738 { 1739 1740 isc->flags &= ~CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1741 } 1742 1743 /* 1744 * Complete a bio. Called before we release the ccb with xpt_release_ccb so we 1745 * might use notes in the ccb for statistics. 1746 */ 1747 int 1748 cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp, 1749 union ccb *done_ccb) 1750 { 1751 int retval = 0; 1752 #ifdef CAM_IOSCHED_DYNAMIC 1753 if (!do_dynamic_iosched) 1754 return retval; 1755 1756 if (iosched_debug > 10) 1757 printf("done: %p %#x\n", bp, bp->bio_cmd); 1758 if (bp->bio_cmd == BIO_WRITE) { 1759 retval = cam_iosched_limiter_iodone(&isc->write_stats, bp); 1760 if ((bp->bio_flags & BIO_ERROR) != 0) 1761 isc->write_stats.errs++; 1762 isc->write_stats.out++; 1763 isc->write_stats.pending--; 1764 } else if (bp->bio_cmd == BIO_READ) { 1765 retval = cam_iosched_limiter_iodone(&isc->read_stats, bp); 1766 if ((bp->bio_flags & BIO_ERROR) != 0) 1767 isc->read_stats.errs++; 1768 isc->read_stats.out++; 1769 isc->read_stats.pending--; 1770 } else if (bp->bio_cmd == BIO_DELETE) { 1771 if ((bp->bio_flags & BIO_ERROR) != 0) 1772 isc->trim_stats.errs++; 1773 isc->trim_stats.out++; 1774 isc->trim_stats.pending--; 1775 } else if (bp->bio_cmd != BIO_FLUSH) { 1776 if (iosched_debug) 1777 printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd); 1778 } 1779 1780 if ((bp->bio_flags & BIO_ERROR) == 0 && done_ccb != NULL && 1781 (done_ccb->ccb_h.status & CAM_QOS_VALID) != 0) { 1782 sbintime_t sim_latency; 1783 1784 sim_latency = cam_iosched_sbintime_t(done_ccb->ccb_h.qos.periph_data); 1785 1786 cam_iosched_io_metric_update(isc, sim_latency, 1787 bp->bio_cmd, bp->bio_bcount); 1788 /* 1789 * Debugging code: allow callbacks to the periph driver when latency max 1790 * is exceeded. This can be useful for triggering external debugging actions. 1791 */ 1792 if (isc->latfcn && isc->max_lat != 0 && sim_latency > isc->max_lat) 1793 isc->latfcn(isc->latarg, sim_latency, bp); 1794 } 1795 1796 #endif 1797 return retval; 1798 } 1799 1800 /* 1801 * Tell the io scheduler that you've pushed a trim down into the sim. 1802 * This also tells the I/O scheduler not to push any more trims down, so 1803 * some periphs do not call it if they can cope with multiple trims in flight. 1804 */ 1805 void 1806 cam_iosched_submit_trim(struct cam_iosched_softc *isc) 1807 { 1808 1809 isc->flags |= CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1810 } 1811 1812 /* 1813 * Change the sorting policy hint for I/O transactions for this device. 1814 */ 1815 void 1816 cam_iosched_set_sort_queue(struct cam_iosched_softc *isc, int val) 1817 { 1818 1819 isc->sort_io_queue = val; 1820 } 1821 1822 int 1823 cam_iosched_has_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1824 { 1825 return isc->flags & flags; 1826 } 1827 1828 void 1829 cam_iosched_set_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1830 { 1831 isc->flags |= flags; 1832 } 1833 1834 void 1835 cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1836 { 1837 isc->flags &= ~flags; 1838 } 1839 1840 #ifdef CAM_IOSCHED_DYNAMIC 1841 /* 1842 * After the method presented in Jack Crenshaw's 1998 article "Integer 1843 * Square Roots," reprinted at 1844 * http://www.embedded.com/electronics-blogs/programmer-s-toolbox/4219659/Integer-Square-Roots 1845 * and well worth the read. Briefly, we find the power of 4 that's the 1846 * largest smaller than val. We then check each smaller power of 4 to 1847 * see if val is still bigger. The right shifts at each step divide 1848 * the result by 2 which after successive application winds up 1849 * accumulating the right answer. It could also have been accumulated 1850 * using a separate root counter, but this code is smaller and faster 1851 * than that method. This method is also integer size invariant. 1852 * It returns floor(sqrt((float)val)), or the largest integer less than 1853 * or equal to the square root. 1854 */ 1855 static uint64_t 1856 isqrt64(uint64_t val) 1857 { 1858 uint64_t res = 0; 1859 uint64_t bit = 1ULL << (sizeof(uint64_t) * NBBY - 2); 1860 1861 /* 1862 * Find the largest power of 4 smaller than val. 1863 */ 1864 while (bit > val) 1865 bit >>= 2; 1866 1867 /* 1868 * Accumulate the answer, one bit at a time (we keep moving 1869 * them over since 2 is the square root of 4 and we test 1870 * powers of 4). We accumulate where we find the bit, but 1871 * the successive shifts land the bit in the right place 1872 * by the end. 1873 */ 1874 while (bit != 0) { 1875 if (val >= res + bit) { 1876 val -= res + bit; 1877 res = (res >> 1) + bit; 1878 } else 1879 res >>= 1; 1880 bit >>= 2; 1881 } 1882 1883 return res; 1884 } 1885 1886 static sbintime_t latencies[LAT_BUCKETS - 1] = { 1887 BUCKET_BASE << 0, /* 20us */ 1888 BUCKET_BASE << 1, 1889 BUCKET_BASE << 2, 1890 BUCKET_BASE << 3, 1891 BUCKET_BASE << 4, 1892 BUCKET_BASE << 5, 1893 BUCKET_BASE << 6, 1894 BUCKET_BASE << 7, 1895 BUCKET_BASE << 8, 1896 BUCKET_BASE << 9, 1897 BUCKET_BASE << 10, 1898 BUCKET_BASE << 11, 1899 BUCKET_BASE << 12, 1900 BUCKET_BASE << 13, 1901 BUCKET_BASE << 14, 1902 BUCKET_BASE << 15, 1903 BUCKET_BASE << 16, 1904 BUCKET_BASE << 17, 1905 BUCKET_BASE << 18 /* 5,242,880us */ 1906 }; 1907 1908 static void 1909 cam_iosched_update(struct iop_stats *iop, sbintime_t sim_latency) 1910 { 1911 sbintime_t y, deltasq, delta; 1912 int i; 1913 1914 /* 1915 * Keep counts for latency. We do it by power of two buckets. 1916 * This helps us spot outlier behavior obscured by averages. 1917 */ 1918 for (i = 0; i < LAT_BUCKETS - 1; i++) { 1919 if (sim_latency < latencies[i]) { 1920 iop->latencies[i]++; 1921 break; 1922 } 1923 } 1924 if (i == LAT_BUCKETS - 1) 1925 iop->latencies[i]++; /* Put all > 8192ms values into the last bucket. */ 1926 1927 /* 1928 * Classic exponentially decaying average with a tiny alpha 1929 * (2 ^ -alpha_bits). For more info see the NIST statistical 1930 * handbook. 1931 * 1932 * ema_t = y_t * alpha + ema_t-1 * (1 - alpha) [nist] 1933 * ema_t = y_t * alpha + ema_t-1 - alpha * ema_t-1 1934 * ema_t = alpha * y_t - alpha * ema_t-1 + ema_t-1 1935 * alpha = 1 / (1 << alpha_bits) 1936 * sub e == ema_t-1, b == 1/alpha (== 1 << alpha_bits), d == y_t - ema_t-1 1937 * = y_t/b - e/b + be/b 1938 * = (y_t - e + be) / b 1939 * = (e + d) / b 1940 * 1941 * Since alpha is a power of two, we can compute this w/o any mult or 1942 * division. 1943 * 1944 * Variance can also be computed. Usually, it would be expressed as follows: 1945 * diff_t = y_t - ema_t-1 1946 * emvar_t = (1 - alpha) * (emavar_t-1 + diff_t^2 * alpha) 1947 * = emavar_t-1 - alpha * emavar_t-1 + delta_t^2 * alpha - (delta_t * alpha)^2 1948 * sub b == 1/alpha (== 1 << alpha_bits), e == emavar_t-1, d = delta_t^2 1949 * = e - e/b + dd/b + dd/bb 1950 * = (bbe - be + bdd + dd) / bb 1951 * = (bbe + b(dd-e) + dd) / bb (which is expanded below bb = 1<<(2*alpha_bits)) 1952 */ 1953 /* 1954 * XXX possible numeric issues 1955 * o We assume right shifted integers do the right thing, since that's 1956 * implementation defined. You can change the right shifts to / (1LL << alpha). 1957 * o alpha_bits = 9 gives ema ceiling of 23 bits of seconds for ema and 14 bits 1958 * for emvar. This puts a ceiling of 13 bits on alpha since we need a 1959 * few tens of seconds of representation. 1960 * o We mitigate alpha issues by never setting it too high. 1961 */ 1962 y = sim_latency; 1963 delta = (y - iop->ema); /* d */ 1964 iop->ema = ((iop->ema << alpha_bits) + delta) >> alpha_bits; 1965 1966 /* 1967 * Were we to naively plow ahead at this point, we wind up with many numerical 1968 * issues making any SD > ~3ms unreliable. So, we shift right by 12. This leaves 1969 * us with microsecond level precision in the input, so the same in the 1970 * output. It means we can't overflow deltasq unless delta > 4k seconds. It 1971 * also means that emvar can be up 46 bits 40 of which are fraction, which 1972 * gives us a way to measure up to ~8s in the SD before the computation goes 1973 * unstable. Even the worst hard disk rarely has > 1s service time in the 1974 * drive. It does mean we have to shift left 12 bits after taking the 1975 * square root to compute the actual standard deviation estimate. This loss of 1976 * precision is preferable to needing int128 types to work. The above numbers 1977 * assume alpha=9. 10 or 11 are ok, but we start to run into issues at 12, 1978 * so 12 or 13 is OK for EMA, EMVAR and SD will be wrong in those cases. 1979 */ 1980 delta >>= 12; 1981 deltasq = delta * delta; /* dd */ 1982 iop->emvar = ((iop->emvar << (2 * alpha_bits)) + /* bbe */ 1983 ((deltasq - iop->emvar) << alpha_bits) + /* b(dd-e) */ 1984 deltasq) /* dd */ 1985 >> (2 * alpha_bits); /* div bb */ 1986 iop->sd = (sbintime_t)isqrt64((uint64_t)iop->emvar) << 12; 1987 } 1988 1989 static void 1990 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 1991 sbintime_t sim_latency, int cmd, size_t size) 1992 { 1993 /* xxx Do we need to scale based on the size of the I/O ? */ 1994 switch (cmd) { 1995 case BIO_READ: 1996 cam_iosched_update(&isc->read_stats, sim_latency); 1997 break; 1998 case BIO_WRITE: 1999 cam_iosched_update(&isc->write_stats, sim_latency); 2000 break; 2001 case BIO_DELETE: 2002 cam_iosched_update(&isc->trim_stats, sim_latency); 2003 break; 2004 default: 2005 break; 2006 } 2007 } 2008 2009 #ifdef DDB 2010 static int biolen(struct bio_queue_head *bq) 2011 { 2012 int i = 0; 2013 struct bio *bp; 2014 2015 TAILQ_FOREACH(bp, &bq->queue, bio_queue) { 2016 i++; 2017 } 2018 return i; 2019 } 2020 2021 /* 2022 * Show the internal state of the I/O scheduler. 2023 */ 2024 DB_SHOW_COMMAND(iosched, cam_iosched_db_show) 2025 { 2026 struct cam_iosched_softc *isc; 2027 2028 if (!have_addr) { 2029 db_printf("Need addr\n"); 2030 return; 2031 } 2032 isc = (struct cam_iosched_softc *)addr; 2033 db_printf("pending_reads: %d\n", isc->read_stats.pending); 2034 db_printf("min_reads: %d\n", isc->read_stats.min); 2035 db_printf("max_reads: %d\n", isc->read_stats.max); 2036 db_printf("reads: %d\n", isc->read_stats.total); 2037 db_printf("in_reads: %d\n", isc->read_stats.in); 2038 db_printf("out_reads: %d\n", isc->read_stats.out); 2039 db_printf("queued_reads: %d\n", isc->read_stats.queued); 2040 db_printf("Read Q len %d\n", biolen(&isc->bio_queue)); 2041 db_printf("pending_writes: %d\n", isc->write_stats.pending); 2042 db_printf("min_writes: %d\n", isc->write_stats.min); 2043 db_printf("max_writes: %d\n", isc->write_stats.max); 2044 db_printf("writes: %d\n", isc->write_stats.total); 2045 db_printf("in_writes: %d\n", isc->write_stats.in); 2046 db_printf("out_writes: %d\n", isc->write_stats.out); 2047 db_printf("queued_writes: %d\n", isc->write_stats.queued); 2048 db_printf("Write Q len %d\n", biolen(&isc->write_queue)); 2049 db_printf("pending_trims: %d\n", isc->trim_stats.pending); 2050 db_printf("min_trims: %d\n", isc->trim_stats.min); 2051 db_printf("max_trims: %d\n", isc->trim_stats.max); 2052 db_printf("trims: %d\n", isc->trim_stats.total); 2053 db_printf("in_trims: %d\n", isc->trim_stats.in); 2054 db_printf("out_trims: %d\n", isc->trim_stats.out); 2055 db_printf("queued_trims: %d\n", isc->trim_stats.queued); 2056 db_printf("Trim Q len %d\n", biolen(&isc->trim_queue)); 2057 db_printf("read_bias: %d\n", isc->read_bias); 2058 db_printf("current_read_bias: %d\n", isc->current_read_bias); 2059 db_printf("Trim active? %s\n", 2060 (isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) ? "yes" : "no"); 2061 } 2062 #endif 2063 #endif 2064