1 /*- 2 * CAM IO Scheduler Interface 3 * 4 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 5 * 6 * Copyright (c) 2015 Netflix, Inc. 7 * All rights reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions, and the following disclaimer, 14 * without modification, immediately at the beginning of the file. 15 * 2. The name of the author may not be used to endorse or promote products 16 * derived from this software without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR 22 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 * 30 * $FreeBSD$ 31 */ 32 33 #include "opt_cam.h" 34 #include "opt_ddb.h" 35 36 #include <sys/cdefs.h> 37 __FBSDID("$FreeBSD$"); 38 39 #include <sys/param.h> 40 41 #include <sys/systm.h> 42 #include <sys/kernel.h> 43 #include <sys/bio.h> 44 #include <sys/lock.h> 45 #include <sys/malloc.h> 46 #include <sys/mutex.h> 47 #include <sys/sbuf.h> 48 #include <sys/sysctl.h> 49 50 #include <cam/cam.h> 51 #include <cam/cam_ccb.h> 52 #include <cam/cam_periph.h> 53 #include <cam/cam_xpt_periph.h> 54 #include <cam/cam_xpt_internal.h> 55 #include <cam/cam_iosched.h> 56 57 #include <ddb/ddb.h> 58 59 static MALLOC_DEFINE(M_CAMSCHED, "CAM I/O Scheduler", 60 "CAM I/O Scheduler buffers"); 61 62 /* 63 * Default I/O scheduler for FreeBSD. This implementation is just a thin-vineer 64 * over the bioq_* interface, with notions of separate calls for normal I/O and 65 * for trims. 66 * 67 * When CAM_IOSCHED_DYNAMIC is defined, the scheduler is enhanced to dynamically 68 * steer the rate of one type of traffic to help other types of traffic (eg 69 * limit writes when read latency deteriorates on SSDs). 70 */ 71 72 #ifdef CAM_IOSCHED_DYNAMIC 73 74 static int do_dynamic_iosched = 1; 75 TUNABLE_INT("kern.cam.do_dynamic_iosched", &do_dynamic_iosched); 76 SYSCTL_INT(_kern_cam, OID_AUTO, do_dynamic_iosched, CTLFLAG_RD, 77 &do_dynamic_iosched, 1, 78 "Enable Dynamic I/O scheduler optimizations."); 79 80 /* 81 * For an EMA, with an alpha of alpha, we know 82 * alpha = 2 / (N + 1) 83 * or 84 * N = 1 + (2 / alpha) 85 * where N is the number of samples that 86% of the current 86 * EMA is derived from. 87 * 88 * So we invent[*] alpha_bits: 89 * alpha_bits = -log_2(alpha) 90 * alpha = 2^-alpha_bits 91 * So 92 * N = 1 + 2^(alpha_bits + 1) 93 * 94 * The default 9 gives a 1025 lookback for 86% of the data. 95 * For a brief intro: https://en.wikipedia.org/wiki/Moving_average 96 * 97 * [*] Steal from the load average code and many other places. 98 * Note: See computation of EMA and EMVAR for acceptable ranges of alpha. 99 */ 100 static int alpha_bits = 9; 101 TUNABLE_INT("kern.cam.iosched_alpha_bits", &alpha_bits); 102 SYSCTL_INT(_kern_cam, OID_AUTO, iosched_alpha_bits, CTLFLAG_RW, 103 &alpha_bits, 1, 104 "Bits in EMA's alpha."); 105 106 struct iop_stats; 107 struct cam_iosched_softc; 108 109 int iosched_debug = 0; 110 111 typedef enum { 112 none = 0, /* No limits */ 113 queue_depth, /* Limit how many ops we queue to SIM */ 114 iops, /* Limit # of IOPS to the drive */ 115 bandwidth, /* Limit bandwidth to the drive */ 116 limiter_max 117 } io_limiter; 118 119 static const char *cam_iosched_limiter_names[] = 120 { "none", "queue_depth", "iops", "bandwidth" }; 121 122 /* 123 * Called to initialize the bits of the iop_stats structure relevant to the 124 * limiter. Called just after the limiter is set. 125 */ 126 typedef int l_init_t(struct iop_stats *); 127 128 /* 129 * Called every tick. 130 */ 131 typedef int l_tick_t(struct iop_stats *); 132 133 /* 134 * Called to see if the limiter thinks this IOP can be allowed to 135 * proceed. If so, the limiter assumes that the IOP proceeded 136 * and makes any accounting of it that's needed. 137 */ 138 typedef int l_iop_t(struct iop_stats *, struct bio *); 139 140 /* 141 * Called when an I/O completes so the limiter can update its 142 * accounting. Pending I/Os may complete in any order (even when 143 * sent to the hardware at the same time), so the limiter may not 144 * make any assumptions other than this I/O has completed. If it 145 * returns 1, then xpt_schedule() needs to be called again. 146 */ 147 typedef int l_iodone_t(struct iop_stats *, struct bio *); 148 149 static l_iop_t cam_iosched_qd_iop; 150 static l_iop_t cam_iosched_qd_caniop; 151 static l_iodone_t cam_iosched_qd_iodone; 152 153 static l_init_t cam_iosched_iops_init; 154 static l_tick_t cam_iosched_iops_tick; 155 static l_iop_t cam_iosched_iops_caniop; 156 static l_iop_t cam_iosched_iops_iop; 157 158 static l_init_t cam_iosched_bw_init; 159 static l_tick_t cam_iosched_bw_tick; 160 static l_iop_t cam_iosched_bw_caniop; 161 static l_iop_t cam_iosched_bw_iop; 162 163 struct limswitch { 164 l_init_t *l_init; 165 l_tick_t *l_tick; 166 l_iop_t *l_iop; 167 l_iop_t *l_caniop; 168 l_iodone_t *l_iodone; 169 } limsw[] = 170 { 171 { /* none */ 172 .l_init = NULL, 173 .l_tick = NULL, 174 .l_iop = NULL, 175 .l_iodone= NULL, 176 }, 177 { /* queue_depth */ 178 .l_init = NULL, 179 .l_tick = NULL, 180 .l_caniop = cam_iosched_qd_caniop, 181 .l_iop = cam_iosched_qd_iop, 182 .l_iodone= cam_iosched_qd_iodone, 183 }, 184 { /* iops */ 185 .l_init = cam_iosched_iops_init, 186 .l_tick = cam_iosched_iops_tick, 187 .l_caniop = cam_iosched_iops_caniop, 188 .l_iop = cam_iosched_iops_iop, 189 .l_iodone= NULL, 190 }, 191 { /* bandwidth */ 192 .l_init = cam_iosched_bw_init, 193 .l_tick = cam_iosched_bw_tick, 194 .l_caniop = cam_iosched_bw_caniop, 195 .l_iop = cam_iosched_bw_iop, 196 .l_iodone= NULL, 197 }, 198 }; 199 200 struct iop_stats { 201 /* 202 * sysctl state for this subnode. 203 */ 204 struct sysctl_ctx_list sysctl_ctx; 205 struct sysctl_oid *sysctl_tree; 206 207 /* 208 * Information about the current rate limiters, if any 209 */ 210 io_limiter limiter; /* How are I/Os being limited */ 211 int min; /* Low range of limit */ 212 int max; /* High range of limit */ 213 int current; /* Current rate limiter */ 214 int l_value1; /* per-limiter scratch value 1. */ 215 int l_value2; /* per-limiter scratch value 2. */ 216 217 /* 218 * Debug information about counts of I/Os that have gone through the 219 * scheduler. 220 */ 221 int pending; /* I/Os pending in the hardware */ 222 int queued; /* number currently in the queue */ 223 int total; /* Total for all time -- wraps */ 224 int in; /* number queued all time -- wraps */ 225 int out; /* number completed all time -- wraps */ 226 int errs; /* Number of I/Os completed with error -- wraps */ 227 228 /* 229 * Statistics on different bits of the process. 230 */ 231 /* Exp Moving Average, see alpha_bits for more details */ 232 sbintime_t ema; 233 sbintime_t emvar; 234 sbintime_t sd; /* Last computed sd */ 235 236 uint32_t state_flags; 237 #define IOP_RATE_LIMITED 1u 238 239 #define LAT_BUCKETS 15 /* < 1ms < 2ms ... < 2^(n-1)ms >= 2^(n-1)ms*/ 240 uint64_t latencies[LAT_BUCKETS]; 241 242 struct cam_iosched_softc *softc; 243 }; 244 245 246 typedef enum { 247 set_max = 0, /* current = max */ 248 read_latency, /* Steer read latency by throttling writes */ 249 cl_max /* Keep last */ 250 } control_type; 251 252 static const char *cam_iosched_control_type_names[] = 253 { "set_max", "read_latency" }; 254 255 struct control_loop { 256 /* 257 * sysctl state for this subnode. 258 */ 259 struct sysctl_ctx_list sysctl_ctx; 260 struct sysctl_oid *sysctl_tree; 261 262 sbintime_t next_steer; /* Time of next steer */ 263 sbintime_t steer_interval; /* How often do we steer? */ 264 sbintime_t lolat; 265 sbintime_t hilat; 266 int alpha; 267 control_type type; /* What type of control? */ 268 int last_count; /* Last I/O count */ 269 270 struct cam_iosched_softc *softc; 271 }; 272 273 #endif 274 275 struct cam_iosched_softc { 276 struct bio_queue_head bio_queue; 277 struct bio_queue_head trim_queue; 278 /* scheduler flags < 16, user flags >= 16 */ 279 uint32_t flags; 280 int sort_io_queue; 281 #ifdef CAM_IOSCHED_DYNAMIC 282 int read_bias; /* Read bias setting */ 283 int current_read_bias; /* Current read bias state */ 284 int total_ticks; 285 int load; /* EMA of 'load average' of disk / 2^16 */ 286 287 struct bio_queue_head write_queue; 288 struct iop_stats read_stats, write_stats, trim_stats; 289 struct sysctl_ctx_list sysctl_ctx; 290 struct sysctl_oid *sysctl_tree; 291 292 int quanta; /* Number of quanta per second */ 293 struct callout ticker; /* Callout for our quota system */ 294 struct cam_periph *periph; /* cam periph associated with this device */ 295 uint32_t this_frac; /* Fraction of a second (1024ths) for this tick */ 296 sbintime_t last_time; /* Last time we ticked */ 297 struct control_loop cl; 298 #endif 299 }; 300 301 #ifdef CAM_IOSCHED_DYNAMIC 302 /* 303 * helper functions to call the limsw functions. 304 */ 305 static int 306 cam_iosched_limiter_init(struct iop_stats *ios) 307 { 308 int lim = ios->limiter; 309 310 /* maybe this should be a kassert */ 311 if (lim < none || lim >= limiter_max) 312 return EINVAL; 313 314 if (limsw[lim].l_init) 315 return limsw[lim].l_init(ios); 316 317 return 0; 318 } 319 320 static int 321 cam_iosched_limiter_tick(struct iop_stats *ios) 322 { 323 int lim = ios->limiter; 324 325 /* maybe this should be a kassert */ 326 if (lim < none || lim >= limiter_max) 327 return EINVAL; 328 329 if (limsw[lim].l_tick) 330 return limsw[lim].l_tick(ios); 331 332 return 0; 333 } 334 335 static int 336 cam_iosched_limiter_iop(struct iop_stats *ios, struct bio *bp) 337 { 338 int lim = ios->limiter; 339 340 /* maybe this should be a kassert */ 341 if (lim < none || lim >= limiter_max) 342 return EINVAL; 343 344 if (limsw[lim].l_iop) 345 return limsw[lim].l_iop(ios, bp); 346 347 return 0; 348 } 349 350 static int 351 cam_iosched_limiter_caniop(struct iop_stats *ios, struct bio *bp) 352 { 353 int lim = ios->limiter; 354 355 /* maybe this should be a kassert */ 356 if (lim < none || lim >= limiter_max) 357 return EINVAL; 358 359 if (limsw[lim].l_caniop) 360 return limsw[lim].l_caniop(ios, bp); 361 362 return 0; 363 } 364 365 static int 366 cam_iosched_limiter_iodone(struct iop_stats *ios, struct bio *bp) 367 { 368 int lim = ios->limiter; 369 370 /* maybe this should be a kassert */ 371 if (lim < none || lim >= limiter_max) 372 return 0; 373 374 if (limsw[lim].l_iodone) 375 return limsw[lim].l_iodone(ios, bp); 376 377 return 0; 378 } 379 380 /* 381 * Functions to implement the different kinds of limiters 382 */ 383 384 static int 385 cam_iosched_qd_iop(struct iop_stats *ios, struct bio *bp) 386 { 387 388 if (ios->current <= 0 || ios->pending < ios->current) 389 return 0; 390 391 return EAGAIN; 392 } 393 394 static int 395 cam_iosched_qd_caniop(struct iop_stats *ios, struct bio *bp) 396 { 397 398 if (ios->current <= 0 || ios->pending < ios->current) 399 return 0; 400 401 return EAGAIN; 402 } 403 404 static int 405 cam_iosched_qd_iodone(struct iop_stats *ios, struct bio *bp) 406 { 407 408 if (ios->current <= 0 || ios->pending != ios->current) 409 return 0; 410 411 return 1; 412 } 413 414 static int 415 cam_iosched_iops_init(struct iop_stats *ios) 416 { 417 418 ios->l_value1 = ios->current / ios->softc->quanta; 419 if (ios->l_value1 <= 0) 420 ios->l_value1 = 1; 421 ios->l_value2 = 0; 422 423 return 0; 424 } 425 426 static int 427 cam_iosched_iops_tick(struct iop_stats *ios) 428 { 429 int new_ios; 430 431 /* 432 * Allow at least one IO per tick until all 433 * the IOs for this interval have been spent. 434 */ 435 new_ios = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16); 436 if (new_ios < 1 && ios->l_value2 < ios->current) { 437 new_ios = 1; 438 ios->l_value2++; 439 } 440 441 /* 442 * If this a new accounting interval, discard any "unspent" ios 443 * granted in the previous interval. Otherwise add the new ios to 444 * the previously granted ones that haven't been spent yet. 445 */ 446 if ((ios->softc->total_ticks % ios->softc->quanta) == 0) { 447 ios->l_value1 = new_ios; 448 ios->l_value2 = 1; 449 } else { 450 ios->l_value1 += new_ios; 451 } 452 453 454 return 0; 455 } 456 457 static int 458 cam_iosched_iops_caniop(struct iop_stats *ios, struct bio *bp) 459 { 460 461 /* 462 * So if we have any more IOPs left, allow it, 463 * otherwise wait. If current iops is 0, treat that 464 * as unlimited as a failsafe. 465 */ 466 if (ios->current > 0 && ios->l_value1 <= 0) 467 return EAGAIN; 468 return 0; 469 } 470 471 static int 472 cam_iosched_iops_iop(struct iop_stats *ios, struct bio *bp) 473 { 474 int rv; 475 476 rv = cam_iosched_limiter_caniop(ios, bp); 477 if (rv == 0) 478 ios->l_value1--; 479 480 return rv; 481 } 482 483 static int 484 cam_iosched_bw_init(struct iop_stats *ios) 485 { 486 487 /* ios->current is in kB/s, so scale to bytes */ 488 ios->l_value1 = ios->current * 1000 / ios->softc->quanta; 489 490 return 0; 491 } 492 493 static int 494 cam_iosched_bw_tick(struct iop_stats *ios) 495 { 496 int bw; 497 498 /* 499 * If we're in the hole for available quota from 500 * the last time, then add the quantum for this. 501 * If we have any left over from last quantum, 502 * then too bad, that's lost. Also, ios->current 503 * is in kB/s, so scale. 504 * 505 * We also allow up to 4 quanta of credits to 506 * accumulate to deal with burstiness. 4 is extremely 507 * arbitrary. 508 */ 509 bw = (int)((ios->current * 1000ull * (uint64_t)ios->softc->this_frac) >> 16); 510 if (ios->l_value1 < bw * 4) 511 ios->l_value1 += bw; 512 513 return 0; 514 } 515 516 static int 517 cam_iosched_bw_caniop(struct iop_stats *ios, struct bio *bp) 518 { 519 /* 520 * So if we have any more bw quota left, allow it, 521 * otherwise wait. Note, we'll go negative and that's 522 * OK. We'll just get a little less next quota. 523 * 524 * Note on going negative: that allows us to process 525 * requests in order better, since we won't allow 526 * shorter reads to get around the long one that we 527 * don't have the quota to do just yet. It also prevents 528 * starvation by being a little more permissive about 529 * what we let through this quantum (to prevent the 530 * starvation), at the cost of getting a little less 531 * next quantum. 532 * 533 * Also note that if the current limit is <= 0, 534 * we treat it as unlimited as a failsafe. 535 */ 536 if (ios->current > 0 && ios->l_value1 <= 0) 537 return EAGAIN; 538 539 540 return 0; 541 } 542 543 static int 544 cam_iosched_bw_iop(struct iop_stats *ios, struct bio *bp) 545 { 546 int rv; 547 548 rv = cam_iosched_limiter_caniop(ios, bp); 549 if (rv == 0) 550 ios->l_value1 -= bp->bio_length; 551 552 return rv; 553 } 554 555 static void cam_iosched_cl_maybe_steer(struct control_loop *clp); 556 557 static void 558 cam_iosched_ticker(void *arg) 559 { 560 struct cam_iosched_softc *isc = arg; 561 sbintime_t now, delta; 562 int pending; 563 564 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc); 565 566 now = sbinuptime(); 567 delta = now - isc->last_time; 568 isc->this_frac = (uint32_t)delta >> 16; /* Note: discards seconds -- should be 0 harmless if not */ 569 isc->last_time = now; 570 571 cam_iosched_cl_maybe_steer(&isc->cl); 572 573 cam_iosched_limiter_tick(&isc->read_stats); 574 cam_iosched_limiter_tick(&isc->write_stats); 575 cam_iosched_limiter_tick(&isc->trim_stats); 576 577 cam_iosched_schedule(isc, isc->periph); 578 579 /* 580 * isc->load is an EMA of the pending I/Os at each tick. The number of 581 * pending I/Os is the sum of the I/Os queued to the hardware, and those 582 * in the software queue that could be queued to the hardware if there 583 * were slots. 584 * 585 * ios_stats.pending is a count of requests in the SIM right now for 586 * each of these types of I/O. So the total pending count is the sum of 587 * these I/Os and the sum of the queued I/Os still in the software queue 588 * for those operations that aren't being rate limited at the moment. 589 * 590 * The reason for the rate limiting bit is because those I/Os 591 * aren't part of the software queued load (since we could 592 * give them to hardware, but choose not to). 593 * 594 * Note: due to a bug in counting pending TRIM in the device, we 595 * don't include them in this count. We count each BIO_DELETE in 596 * the pending count, but the periph drivers collapse them down 597 * into one TRIM command. That one trim command gets the completion 598 * so the counts get off. 599 */ 600 pending = isc->read_stats.pending + isc->write_stats.pending /* + isc->trim_stats.pending */; 601 pending += !!(isc->read_stats.state_flags & IOP_RATE_LIMITED) * isc->read_stats.queued + 602 !!(isc->write_stats.state_flags & IOP_RATE_LIMITED) * isc->write_stats.queued /* + 603 !!(isc->trim_stats.state_flags & IOP_RATE_LIMITED) * isc->trim_stats.queued */ ; 604 pending <<= 16; 605 pending /= isc->periph->path->device->ccbq.total_openings; 606 607 isc->load = (pending + (isc->load << 13) - isc->load) >> 13; /* see above: 13 -> 16139 / 200/s = ~81s ~1 minute */ 608 609 isc->total_ticks++; 610 } 611 612 613 static void 614 cam_iosched_cl_init(struct control_loop *clp, struct cam_iosched_softc *isc) 615 { 616 617 clp->next_steer = sbinuptime(); 618 clp->softc = isc; 619 clp->steer_interval = SBT_1S * 5; /* Let's start out steering every 5s */ 620 clp->lolat = 5 * SBT_1MS; 621 clp->hilat = 15 * SBT_1MS; 622 clp->alpha = 20; /* Alpha == gain. 20 = .2 */ 623 clp->type = set_max; 624 } 625 626 static void 627 cam_iosched_cl_maybe_steer(struct control_loop *clp) 628 { 629 struct cam_iosched_softc *isc; 630 sbintime_t now, lat; 631 int old; 632 633 isc = clp->softc; 634 now = isc->last_time; 635 if (now < clp->next_steer) 636 return; 637 638 clp->next_steer = now + clp->steer_interval; 639 switch (clp->type) { 640 case set_max: 641 if (isc->write_stats.current != isc->write_stats.max) 642 printf("Steering write from %d kBps to %d kBps\n", 643 isc->write_stats.current, isc->write_stats.max); 644 isc->read_stats.current = isc->read_stats.max; 645 isc->write_stats.current = isc->write_stats.max; 646 isc->trim_stats.current = isc->trim_stats.max; 647 break; 648 case read_latency: 649 old = isc->write_stats.current; 650 lat = isc->read_stats.ema; 651 /* 652 * Simple PLL-like engine. Since we're steering to a range for 653 * the SP (set point) that makes things a little more 654 * complicated. In addition, we're not directly controlling our 655 * PV (process variable), the read latency, but instead are 656 * manipulating the write bandwidth limit for our MV 657 * (manipulation variable), analysis of this code gets a bit 658 * messy. Also, the MV is a very noisy control surface for read 659 * latency since it is affected by many hidden processes inside 660 * the device which change how responsive read latency will be 661 * in reaction to changes in write bandwidth. Unlike the classic 662 * boiler control PLL. this may result in over-steering while 663 * the SSD takes its time to react to the new, lower load. This 664 * is why we use a relatively low alpha of between .1 and .25 to 665 * compensate for this effect. At .1, it takes ~22 steering 666 * intervals to back off by a factor of 10. At .2 it only takes 667 * ~10. At .25 it only takes ~8. However some preliminary data 668 * from the SSD drives suggests a reasponse time in 10's of 669 * seconds before latency drops regardless of the new write 670 * rate. Careful observation will be required to tune this 671 * effectively. 672 * 673 * Also, when there's no read traffic, we jack up the write 674 * limit too regardless of the last read latency. 10 is 675 * somewhat arbitrary. 676 */ 677 if (lat < clp->lolat || isc->read_stats.total - clp->last_count < 10) 678 isc->write_stats.current = isc->write_stats.current * 679 (100 + clp->alpha) / 100; /* Scale up */ 680 else if (lat > clp->hilat) 681 isc->write_stats.current = isc->write_stats.current * 682 (100 - clp->alpha) / 100; /* Scale down */ 683 clp->last_count = isc->read_stats.total; 684 685 /* 686 * Even if we don't steer, per se, enforce the min/max limits as 687 * those may have changed. 688 */ 689 if (isc->write_stats.current < isc->write_stats.min) 690 isc->write_stats.current = isc->write_stats.min; 691 if (isc->write_stats.current > isc->write_stats.max) 692 isc->write_stats.current = isc->write_stats.max; 693 if (old != isc->write_stats.current && iosched_debug) 694 printf("Steering write from %d kBps to %d kBps due to latency of %jdus\n", 695 old, isc->write_stats.current, 696 (uintmax_t)((uint64_t)1000000 * (uint32_t)lat) >> 32); 697 break; 698 case cl_max: 699 break; 700 } 701 } 702 #endif 703 704 /* 705 * Trim or similar currently pending completion. Should only be set for 706 * those drivers wishing only one Trim active at a time. 707 */ 708 #define CAM_IOSCHED_FLAG_TRIM_ACTIVE (1ul << 0) 709 /* Callout active, and needs to be torn down */ 710 #define CAM_IOSCHED_FLAG_CALLOUT_ACTIVE (1ul << 1) 711 712 /* Periph drivers set these flags to indicate work */ 713 #define CAM_IOSCHED_FLAG_WORK_FLAGS ((0xffffu) << 16) 714 715 #ifdef CAM_IOSCHED_DYNAMIC 716 static void 717 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 718 sbintime_t sim_latency, int cmd, size_t size); 719 #endif 720 721 static inline bool 722 cam_iosched_has_flagged_work(struct cam_iosched_softc *isc) 723 { 724 return !!(isc->flags & CAM_IOSCHED_FLAG_WORK_FLAGS); 725 } 726 727 static inline bool 728 cam_iosched_has_io(struct cam_iosched_softc *isc) 729 { 730 #ifdef CAM_IOSCHED_DYNAMIC 731 if (do_dynamic_iosched) { 732 struct bio *rbp = bioq_first(&isc->bio_queue); 733 struct bio *wbp = bioq_first(&isc->write_queue); 734 bool can_write = wbp != NULL && 735 cam_iosched_limiter_caniop(&isc->write_stats, wbp) == 0; 736 bool can_read = rbp != NULL && 737 cam_iosched_limiter_caniop(&isc->read_stats, rbp) == 0; 738 if (iosched_debug > 2) { 739 printf("can write %d: pending_writes %d max_writes %d\n", can_write, isc->write_stats.pending, isc->write_stats.max); 740 printf("can read %d: read_stats.pending %d max_reads %d\n", can_read, isc->read_stats.pending, isc->read_stats.max); 741 printf("Queued reads %d writes %d\n", isc->read_stats.queued, isc->write_stats.queued); 742 } 743 return can_read || can_write; 744 } 745 #endif 746 return bioq_first(&isc->bio_queue) != NULL; 747 } 748 749 static inline bool 750 cam_iosched_has_more_trim(struct cam_iosched_softc *isc) 751 { 752 return !(isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) && 753 bioq_first(&isc->trim_queue); 754 } 755 756 #define cam_iosched_sort_queue(isc) ((isc)->sort_io_queue >= 0 ? \ 757 (isc)->sort_io_queue : cam_sort_io_queues) 758 759 760 static inline bool 761 cam_iosched_has_work(struct cam_iosched_softc *isc) 762 { 763 #ifdef CAM_IOSCHED_DYNAMIC 764 if (iosched_debug > 2) 765 printf("has work: %d %d %d\n", cam_iosched_has_io(isc), 766 cam_iosched_has_more_trim(isc), 767 cam_iosched_has_flagged_work(isc)); 768 #endif 769 770 return cam_iosched_has_io(isc) || 771 cam_iosched_has_more_trim(isc) || 772 cam_iosched_has_flagged_work(isc); 773 } 774 775 #ifdef CAM_IOSCHED_DYNAMIC 776 static void 777 cam_iosched_iop_stats_init(struct cam_iosched_softc *isc, struct iop_stats *ios) 778 { 779 780 ios->limiter = none; 781 ios->in = 0; 782 ios->max = ios->current = 300000; 783 ios->min = 1; 784 ios->out = 0; 785 ios->errs = 0; 786 ios->pending = 0; 787 ios->queued = 0; 788 ios->total = 0; 789 ios->ema = 0; 790 ios->emvar = 0; 791 ios->softc = isc; 792 cam_iosched_limiter_init(ios); 793 } 794 795 static int 796 cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS) 797 { 798 char buf[16]; 799 struct iop_stats *ios; 800 struct cam_iosched_softc *isc; 801 int value, i, error; 802 const char *p; 803 804 ios = arg1; 805 isc = ios->softc; 806 value = ios->limiter; 807 if (value < none || value >= limiter_max) 808 p = "UNKNOWN"; 809 else 810 p = cam_iosched_limiter_names[value]; 811 812 strlcpy(buf, p, sizeof(buf)); 813 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 814 if (error != 0 || req->newptr == NULL) 815 return error; 816 817 cam_periph_lock(isc->periph); 818 819 for (i = none; i < limiter_max; i++) { 820 if (strcmp(buf, cam_iosched_limiter_names[i]) != 0) 821 continue; 822 ios->limiter = i; 823 error = cam_iosched_limiter_init(ios); 824 if (error != 0) { 825 ios->limiter = value; 826 cam_periph_unlock(isc->periph); 827 return error; 828 } 829 /* Note: disk load averate requires ticker to be always running */ 830 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc); 831 isc->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 832 833 cam_periph_unlock(isc->periph); 834 return 0; 835 } 836 837 cam_periph_unlock(isc->periph); 838 return EINVAL; 839 } 840 841 static int 842 cam_iosched_control_type_sysctl(SYSCTL_HANDLER_ARGS) 843 { 844 char buf[16]; 845 struct control_loop *clp; 846 struct cam_iosched_softc *isc; 847 int value, i, error; 848 const char *p; 849 850 clp = arg1; 851 isc = clp->softc; 852 value = clp->type; 853 if (value < none || value >= cl_max) 854 p = "UNKNOWN"; 855 else 856 p = cam_iosched_control_type_names[value]; 857 858 strlcpy(buf, p, sizeof(buf)); 859 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 860 if (error != 0 || req->newptr == NULL) 861 return error; 862 863 for (i = set_max; i < cl_max; i++) { 864 if (strcmp(buf, cam_iosched_control_type_names[i]) != 0) 865 continue; 866 cam_periph_lock(isc->periph); 867 clp->type = i; 868 cam_periph_unlock(isc->periph); 869 return 0; 870 } 871 872 return EINVAL; 873 } 874 875 static int 876 cam_iosched_sbintime_sysctl(SYSCTL_HANDLER_ARGS) 877 { 878 char buf[16]; 879 sbintime_t value; 880 int error; 881 uint64_t us; 882 883 value = *(sbintime_t *)arg1; 884 us = (uint64_t)value / SBT_1US; 885 snprintf(buf, sizeof(buf), "%ju", (intmax_t)us); 886 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 887 if (error != 0 || req->newptr == NULL) 888 return error; 889 us = strtoul(buf, NULL, 10); 890 if (us == 0) 891 return EINVAL; 892 *(sbintime_t *)arg1 = us * SBT_1US; 893 return 0; 894 } 895 896 static int 897 cam_iosched_sysctl_latencies(SYSCTL_HANDLER_ARGS) 898 { 899 int i, error; 900 struct sbuf sb; 901 uint64_t *latencies; 902 903 latencies = arg1; 904 sbuf_new_for_sysctl(&sb, NULL, LAT_BUCKETS * 16, req); 905 906 for (i = 0; i < LAT_BUCKETS - 1; i++) 907 sbuf_printf(&sb, "%jd,", (intmax_t)latencies[i]); 908 sbuf_printf(&sb, "%jd", (intmax_t)latencies[LAT_BUCKETS - 1]); 909 error = sbuf_finish(&sb); 910 sbuf_delete(&sb); 911 912 return (error); 913 } 914 915 static int 916 cam_iosched_quanta_sysctl(SYSCTL_HANDLER_ARGS) 917 { 918 int *quanta; 919 int error, value; 920 921 quanta = (unsigned *)arg1; 922 value = *quanta; 923 924 error = sysctl_handle_int(oidp, (int *)&value, 0, req); 925 if ((error != 0) || (req->newptr == NULL)) 926 return (error); 927 928 if (value < 1 || value > hz) 929 return (EINVAL); 930 931 *quanta = value; 932 933 return (0); 934 } 935 936 static void 937 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct iop_stats *ios, char *name) 938 { 939 struct sysctl_oid_list *n; 940 struct sysctl_ctx_list *ctx; 941 942 ios->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 943 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, name, 944 CTLFLAG_RD, 0, name); 945 n = SYSCTL_CHILDREN(ios->sysctl_tree); 946 ctx = &ios->sysctl_ctx; 947 948 SYSCTL_ADD_UQUAD(ctx, n, 949 OID_AUTO, "ema", CTLFLAG_RD, 950 &ios->ema, 951 "Fast Exponentially Weighted Moving Average"); 952 SYSCTL_ADD_UQUAD(ctx, n, 953 OID_AUTO, "emvar", CTLFLAG_RD, 954 &ios->emvar, 955 "Fast Exponentially Weighted Moving Variance"); 956 957 SYSCTL_ADD_INT(ctx, n, 958 OID_AUTO, "pending", CTLFLAG_RD, 959 &ios->pending, 0, 960 "Instantaneous # of pending transactions"); 961 SYSCTL_ADD_INT(ctx, n, 962 OID_AUTO, "count", CTLFLAG_RD, 963 &ios->total, 0, 964 "# of transactions submitted to hardware"); 965 SYSCTL_ADD_INT(ctx, n, 966 OID_AUTO, "queued", CTLFLAG_RD, 967 &ios->queued, 0, 968 "# of transactions in the queue"); 969 SYSCTL_ADD_INT(ctx, n, 970 OID_AUTO, "in", CTLFLAG_RD, 971 &ios->in, 0, 972 "# of transactions queued to driver"); 973 SYSCTL_ADD_INT(ctx, n, 974 OID_AUTO, "out", CTLFLAG_RD, 975 &ios->out, 0, 976 "# of transactions completed (including with error)"); 977 SYSCTL_ADD_INT(ctx, n, 978 OID_AUTO, "errs", CTLFLAG_RD, 979 &ios->errs, 0, 980 "# of transactions completed with an error"); 981 982 SYSCTL_ADD_PROC(ctx, n, 983 OID_AUTO, "limiter", CTLTYPE_STRING | CTLFLAG_RW, 984 ios, 0, cam_iosched_limiter_sysctl, "A", 985 "Current limiting type."); 986 SYSCTL_ADD_INT(ctx, n, 987 OID_AUTO, "min", CTLFLAG_RW, 988 &ios->min, 0, 989 "min resource"); 990 SYSCTL_ADD_INT(ctx, n, 991 OID_AUTO, "max", CTLFLAG_RW, 992 &ios->max, 0, 993 "max resource"); 994 SYSCTL_ADD_INT(ctx, n, 995 OID_AUTO, "current", CTLFLAG_RW, 996 &ios->current, 0, 997 "current resource"); 998 999 SYSCTL_ADD_PROC(ctx, n, 1000 OID_AUTO, "latencies", CTLTYPE_STRING | CTLFLAG_RD, 1001 &ios->latencies, 0, 1002 cam_iosched_sysctl_latencies, "A", 1003 "Array of power of 2 latency from 1ms to 1.024s"); 1004 } 1005 1006 static void 1007 cam_iosched_iop_stats_fini(struct iop_stats *ios) 1008 { 1009 if (ios->sysctl_tree) 1010 if (sysctl_ctx_free(&ios->sysctl_ctx) != 0) 1011 printf("can't remove iosched sysctl stats context\n"); 1012 } 1013 1014 static void 1015 cam_iosched_cl_sysctl_init(struct cam_iosched_softc *isc) 1016 { 1017 struct sysctl_oid_list *n; 1018 struct sysctl_ctx_list *ctx; 1019 struct control_loop *clp; 1020 1021 clp = &isc->cl; 1022 clp->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1023 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, "control", 1024 CTLFLAG_RD, 0, "Control loop info"); 1025 n = SYSCTL_CHILDREN(clp->sysctl_tree); 1026 ctx = &clp->sysctl_ctx; 1027 1028 SYSCTL_ADD_PROC(ctx, n, 1029 OID_AUTO, "type", CTLTYPE_STRING | CTLFLAG_RW, 1030 clp, 0, cam_iosched_control_type_sysctl, "A", 1031 "Control loop algorithm"); 1032 SYSCTL_ADD_PROC(ctx, n, 1033 OID_AUTO, "steer_interval", CTLTYPE_STRING | CTLFLAG_RW, 1034 &clp->steer_interval, 0, cam_iosched_sbintime_sysctl, "A", 1035 "How often to steer (in us)"); 1036 SYSCTL_ADD_PROC(ctx, n, 1037 OID_AUTO, "lolat", CTLTYPE_STRING | CTLFLAG_RW, 1038 &clp->lolat, 0, cam_iosched_sbintime_sysctl, "A", 1039 "Low water mark for Latency (in us)"); 1040 SYSCTL_ADD_PROC(ctx, n, 1041 OID_AUTO, "hilat", CTLTYPE_STRING | CTLFLAG_RW, 1042 &clp->hilat, 0, cam_iosched_sbintime_sysctl, "A", 1043 "Hi water mark for Latency (in us)"); 1044 SYSCTL_ADD_INT(ctx, n, 1045 OID_AUTO, "alpha", CTLFLAG_RW, 1046 &clp->alpha, 0, 1047 "Alpha for PLL (x100) aka gain"); 1048 } 1049 1050 static void 1051 cam_iosched_cl_sysctl_fini(struct control_loop *clp) 1052 { 1053 if (clp->sysctl_tree) 1054 if (sysctl_ctx_free(&clp->sysctl_ctx) != 0) 1055 printf("can't remove iosched sysctl control loop context\n"); 1056 } 1057 #endif 1058 1059 /* 1060 * Allocate the iosched structure. This also insulates callers from knowing 1061 * sizeof struct cam_iosched_softc. 1062 */ 1063 int 1064 cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph) 1065 { 1066 1067 *iscp = malloc(sizeof(**iscp), M_CAMSCHED, M_NOWAIT | M_ZERO); 1068 if (*iscp == NULL) 1069 return ENOMEM; 1070 #ifdef CAM_IOSCHED_DYNAMIC 1071 if (iosched_debug) 1072 printf("CAM IOSCHEDULER Allocating entry at %p\n", *iscp); 1073 #endif 1074 (*iscp)->sort_io_queue = -1; 1075 bioq_init(&(*iscp)->bio_queue); 1076 bioq_init(&(*iscp)->trim_queue); 1077 #ifdef CAM_IOSCHED_DYNAMIC 1078 if (do_dynamic_iosched) { 1079 bioq_init(&(*iscp)->write_queue); 1080 (*iscp)->read_bias = 100; 1081 (*iscp)->current_read_bias = 100; 1082 (*iscp)->quanta = min(hz, 200); 1083 cam_iosched_iop_stats_init(*iscp, &(*iscp)->read_stats); 1084 cam_iosched_iop_stats_init(*iscp, &(*iscp)->write_stats); 1085 cam_iosched_iop_stats_init(*iscp, &(*iscp)->trim_stats); 1086 (*iscp)->trim_stats.max = 1; /* Trims are special: one at a time for now */ 1087 (*iscp)->last_time = sbinuptime(); 1088 callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0); 1089 (*iscp)->periph = periph; 1090 cam_iosched_cl_init(&(*iscp)->cl, *iscp); 1091 callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta, cam_iosched_ticker, *iscp); 1092 (*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1093 } 1094 #endif 1095 1096 return 0; 1097 } 1098 1099 /* 1100 * Reclaim all used resources. This assumes that other folks have 1101 * drained the requests in the hardware. Maybe an unwise assumption. 1102 */ 1103 void 1104 cam_iosched_fini(struct cam_iosched_softc *isc) 1105 { 1106 if (isc) { 1107 cam_iosched_flush(isc, NULL, ENXIO); 1108 #ifdef CAM_IOSCHED_DYNAMIC 1109 cam_iosched_iop_stats_fini(&isc->read_stats); 1110 cam_iosched_iop_stats_fini(&isc->write_stats); 1111 cam_iosched_iop_stats_fini(&isc->trim_stats); 1112 cam_iosched_cl_sysctl_fini(&isc->cl); 1113 if (isc->sysctl_tree) 1114 if (sysctl_ctx_free(&isc->sysctl_ctx) != 0) 1115 printf("can't remove iosched sysctl stats context\n"); 1116 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) { 1117 callout_drain(&isc->ticker); 1118 isc->flags &= ~ CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1119 } 1120 #endif 1121 free(isc, M_CAMSCHED); 1122 } 1123 } 1124 1125 /* 1126 * After we're sure we're attaching a device, go ahead and add 1127 * hooks for any sysctl we may wish to honor. 1128 */ 1129 void cam_iosched_sysctl_init(struct cam_iosched_softc *isc, 1130 struct sysctl_ctx_list *ctx, struct sysctl_oid *node) 1131 { 1132 #ifdef CAM_IOSCHED_DYNAMIC 1133 struct sysctl_oid_list *n; 1134 #endif 1135 1136 SYSCTL_ADD_INT(ctx, SYSCTL_CHILDREN(node), 1137 OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE, 1138 &isc->sort_io_queue, 0, 1139 "Sort IO queue to try and optimise disk access patterns"); 1140 1141 #ifdef CAM_IOSCHED_DYNAMIC 1142 if (!do_dynamic_iosched) 1143 return; 1144 1145 isc->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1146 SYSCTL_CHILDREN(node), OID_AUTO, "iosched", 1147 CTLFLAG_RD, 0, "I/O scheduler statistics"); 1148 n = SYSCTL_CHILDREN(isc->sysctl_tree); 1149 ctx = &isc->sysctl_ctx; 1150 1151 cam_iosched_iop_stats_sysctl_init(isc, &isc->read_stats, "read"); 1152 cam_iosched_iop_stats_sysctl_init(isc, &isc->write_stats, "write"); 1153 cam_iosched_iop_stats_sysctl_init(isc, &isc->trim_stats, "trim"); 1154 cam_iosched_cl_sysctl_init(isc); 1155 1156 SYSCTL_ADD_INT(ctx, n, 1157 OID_AUTO, "read_bias", CTLFLAG_RW, 1158 &isc->read_bias, 100, 1159 "How biased towards read should we be independent of limits"); 1160 1161 SYSCTL_ADD_PROC(ctx, n, 1162 OID_AUTO, "quanta", CTLTYPE_UINT | CTLFLAG_RW, 1163 &isc->quanta, 0, cam_iosched_quanta_sysctl, "I", 1164 "How many quanta per second do we slice the I/O up into"); 1165 1166 SYSCTL_ADD_INT(ctx, n, 1167 OID_AUTO, "total_ticks", CTLFLAG_RD, 1168 &isc->total_ticks, 0, 1169 "Total number of ticks we've done"); 1170 1171 SYSCTL_ADD_INT(ctx, n, 1172 OID_AUTO, "load", CTLFLAG_RD, 1173 &isc->load, 0, 1174 "scaled load average / 100"); 1175 #endif 1176 } 1177 1178 /* 1179 * Flush outstanding I/O. Consumers of this library don't know all the 1180 * queues we may keep, so this allows all I/O to be flushed in one 1181 * convenient call. 1182 */ 1183 void 1184 cam_iosched_flush(struct cam_iosched_softc *isc, struct devstat *stp, int err) 1185 { 1186 bioq_flush(&isc->bio_queue, stp, err); 1187 bioq_flush(&isc->trim_queue, stp, err); 1188 #ifdef CAM_IOSCHED_DYNAMIC 1189 if (do_dynamic_iosched) 1190 bioq_flush(&isc->write_queue, stp, err); 1191 #endif 1192 } 1193 1194 #ifdef CAM_IOSCHED_DYNAMIC 1195 static struct bio * 1196 cam_iosched_get_write(struct cam_iosched_softc *isc) 1197 { 1198 struct bio *bp; 1199 1200 /* 1201 * We control the write rate by controlling how many requests we send 1202 * down to the drive at any one time. Fewer requests limits the 1203 * effects of both starvation when the requests take a while and write 1204 * amplification when each request is causing more than one write to 1205 * the NAND media. Limiting the queue depth like this will also limit 1206 * the write throughput and give and reads that want to compete to 1207 * compete unfairly. 1208 */ 1209 bp = bioq_first(&isc->write_queue); 1210 if (bp == NULL) { 1211 if (iosched_debug > 3) 1212 printf("No writes present in write_queue\n"); 1213 return NULL; 1214 } 1215 1216 /* 1217 * If pending read, prefer that based on current read bias 1218 * setting. 1219 */ 1220 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) { 1221 if (iosched_debug) 1222 printf( 1223 "Reads present and current_read_bias is %d queued " 1224 "writes %d queued reads %d\n", 1225 isc->current_read_bias, isc->write_stats.queued, 1226 isc->read_stats.queued); 1227 isc->current_read_bias--; 1228 /* We're not limiting writes, per se, just doing reads first */ 1229 return NULL; 1230 } 1231 1232 /* 1233 * See if our current limiter allows this I/O. 1234 */ 1235 if (cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) { 1236 if (iosched_debug) 1237 printf("Can't write because limiter says no.\n"); 1238 isc->write_stats.state_flags |= IOP_RATE_LIMITED; 1239 return NULL; 1240 } 1241 1242 /* 1243 * Let's do this: We've passed all the gates and we're a go 1244 * to schedule the I/O in the SIM. 1245 */ 1246 isc->current_read_bias = isc->read_bias; 1247 bioq_remove(&isc->write_queue, bp); 1248 if (bp->bio_cmd == BIO_WRITE) { 1249 isc->write_stats.queued--; 1250 isc->write_stats.total++; 1251 isc->write_stats.pending++; 1252 } 1253 if (iosched_debug > 9) 1254 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1255 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED; 1256 return bp; 1257 } 1258 #endif 1259 1260 /* 1261 * Put back a trim that you weren't able to actually schedule this time. 1262 */ 1263 void 1264 cam_iosched_put_back_trim(struct cam_iosched_softc *isc, struct bio *bp) 1265 { 1266 bioq_insert_head(&isc->trim_queue, bp); 1267 #ifdef CAM_IOSCHED_DYNAMIC 1268 isc->trim_stats.queued++; 1269 isc->trim_stats.total--; /* since we put it back, don't double count */ 1270 isc->trim_stats.pending--; 1271 #endif 1272 } 1273 1274 /* 1275 * gets the next trim from the trim queue. 1276 * 1277 * Assumes we're called with the periph lock held. It removes this 1278 * trim from the queue and the device must explicitly reinsert it 1279 * should the need arise. 1280 */ 1281 struct bio * 1282 cam_iosched_next_trim(struct cam_iosched_softc *isc) 1283 { 1284 struct bio *bp; 1285 1286 bp = bioq_first(&isc->trim_queue); 1287 if (bp == NULL) 1288 return NULL; 1289 bioq_remove(&isc->trim_queue, bp); 1290 #ifdef CAM_IOSCHED_DYNAMIC 1291 isc->trim_stats.queued--; 1292 isc->trim_stats.total++; 1293 isc->trim_stats.pending++; 1294 #endif 1295 return bp; 1296 } 1297 1298 /* 1299 * gets an available trim from the trim queue, if there's no trim 1300 * already pending. It removes this trim from the queue and the device 1301 * must explicitly reinsert it should the need arise. 1302 * 1303 * Assumes we're called with the periph lock held. 1304 */ 1305 struct bio * 1306 cam_iosched_get_trim(struct cam_iosched_softc *isc) 1307 { 1308 1309 if (!cam_iosched_has_more_trim(isc)) 1310 return NULL; 1311 1312 return cam_iosched_next_trim(isc); 1313 } 1314 1315 /* 1316 * Determine what the next bit of work to do is for the periph. The 1317 * default implementation looks to see if we have trims to do, but no 1318 * trims outstanding. If so, we do that. Otherwise we see if we have 1319 * other work. If we do, then we do that. Otherwise why were we called? 1320 */ 1321 struct bio * 1322 cam_iosched_next_bio(struct cam_iosched_softc *isc) 1323 { 1324 struct bio *bp; 1325 1326 /* 1327 * See if we have a trim that can be scheduled. We can only send one 1328 * at a time down, so this takes that into account. 1329 * 1330 * XXX newer TRIM commands are queueable. Revisit this when we 1331 * implement them. 1332 */ 1333 if ((bp = cam_iosched_get_trim(isc)) != NULL) 1334 return bp; 1335 1336 #ifdef CAM_IOSCHED_DYNAMIC 1337 /* 1338 * See if we have any pending writes, and room in the queue for them, 1339 * and if so, those are next. 1340 */ 1341 if (do_dynamic_iosched) { 1342 if ((bp = cam_iosched_get_write(isc)) != NULL) 1343 return bp; 1344 } 1345 #endif 1346 1347 /* 1348 * next, see if there's other, normal I/O waiting. If so return that. 1349 */ 1350 if ((bp = bioq_first(&isc->bio_queue)) == NULL) 1351 return NULL; 1352 1353 #ifdef CAM_IOSCHED_DYNAMIC 1354 /* 1355 * For the dynamic scheduler, bio_queue is only for reads, so enforce 1356 * the limits here. Enforce only for reads. 1357 */ 1358 if (do_dynamic_iosched) { 1359 if (bp->bio_cmd == BIO_READ && 1360 cam_iosched_limiter_iop(&isc->read_stats, bp) != 0) { 1361 isc->read_stats.state_flags |= IOP_RATE_LIMITED; 1362 return NULL; 1363 } 1364 } 1365 isc->read_stats.state_flags &= ~IOP_RATE_LIMITED; 1366 #endif 1367 bioq_remove(&isc->bio_queue, bp); 1368 #ifdef CAM_IOSCHED_DYNAMIC 1369 if (do_dynamic_iosched) { 1370 if (bp->bio_cmd == BIO_READ) { 1371 isc->read_stats.queued--; 1372 isc->read_stats.total++; 1373 isc->read_stats.pending++; 1374 } else 1375 printf("Found bio_cmd = %#x\n", bp->bio_cmd); 1376 } 1377 if (iosched_debug > 9) 1378 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1379 #endif 1380 return bp; 1381 } 1382 1383 /* 1384 * Driver has been given some work to do by the block layer. Tell the 1385 * scheduler about it and have it queue the work up. The scheduler module 1386 * will then return the currently most useful bit of work later, possibly 1387 * deferring work for various reasons. 1388 */ 1389 void 1390 cam_iosched_queue_work(struct cam_iosched_softc *isc, struct bio *bp) 1391 { 1392 1393 /* 1394 * Put all trims on the trim queue sorted, since we know 1395 * that the collapsing code requires this. Otherwise put 1396 * the work on the bio queue. 1397 */ 1398 if (bp->bio_cmd == BIO_DELETE) { 1399 bioq_insert_tail(&isc->trim_queue, bp); 1400 #ifdef CAM_IOSCHED_DYNAMIC 1401 isc->trim_stats.in++; 1402 isc->trim_stats.queued++; 1403 #endif 1404 } 1405 #ifdef CAM_IOSCHED_DYNAMIC 1406 else if (do_dynamic_iosched && (bp->bio_cmd != BIO_READ)) { 1407 if (cam_iosched_sort_queue(isc)) 1408 bioq_disksort(&isc->write_queue, bp); 1409 else 1410 bioq_insert_tail(&isc->write_queue, bp); 1411 if (iosched_debug > 9) 1412 printf("Qw : %p %#x\n", bp, bp->bio_cmd); 1413 if (bp->bio_cmd == BIO_WRITE) { 1414 isc->write_stats.in++; 1415 isc->write_stats.queued++; 1416 } 1417 } 1418 #endif 1419 else { 1420 if (cam_iosched_sort_queue(isc)) 1421 bioq_disksort(&isc->bio_queue, bp); 1422 else 1423 bioq_insert_tail(&isc->bio_queue, bp); 1424 #ifdef CAM_IOSCHED_DYNAMIC 1425 if (iosched_debug > 9) 1426 printf("Qr : %p %#x\n", bp, bp->bio_cmd); 1427 if (bp->bio_cmd == BIO_READ) { 1428 isc->read_stats.in++; 1429 isc->read_stats.queued++; 1430 } else if (bp->bio_cmd == BIO_WRITE) { 1431 isc->write_stats.in++; 1432 isc->write_stats.queued++; 1433 } 1434 #endif 1435 } 1436 } 1437 1438 /* 1439 * If we have work, get it scheduled. Called with the periph lock held. 1440 */ 1441 void 1442 cam_iosched_schedule(struct cam_iosched_softc *isc, struct cam_periph *periph) 1443 { 1444 1445 if (cam_iosched_has_work(isc)) 1446 xpt_schedule(periph, CAM_PRIORITY_NORMAL); 1447 } 1448 1449 /* 1450 * Complete a trim request. Mark that we no longer have one in flight. 1451 */ 1452 void 1453 cam_iosched_trim_done(struct cam_iosched_softc *isc) 1454 { 1455 1456 isc->flags &= ~CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1457 } 1458 1459 /* 1460 * Complete a bio. Called before we release the ccb with xpt_release_ccb so we 1461 * might use notes in the ccb for statistics. 1462 */ 1463 int 1464 cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp, 1465 union ccb *done_ccb) 1466 { 1467 int retval = 0; 1468 #ifdef CAM_IOSCHED_DYNAMIC 1469 if (!do_dynamic_iosched) 1470 return retval; 1471 1472 if (iosched_debug > 10) 1473 printf("done: %p %#x\n", bp, bp->bio_cmd); 1474 if (bp->bio_cmd == BIO_WRITE) { 1475 retval = cam_iosched_limiter_iodone(&isc->write_stats, bp); 1476 if (!(bp->bio_flags & BIO_ERROR)) 1477 isc->write_stats.errs++; 1478 isc->write_stats.out++; 1479 isc->write_stats.pending--; 1480 } else if (bp->bio_cmd == BIO_READ) { 1481 retval = cam_iosched_limiter_iodone(&isc->read_stats, bp); 1482 if (!(bp->bio_flags & BIO_ERROR)) 1483 isc->read_stats.errs++; 1484 isc->read_stats.out++; 1485 isc->read_stats.pending--; 1486 } else if (bp->bio_cmd == BIO_DELETE) { 1487 if (!(bp->bio_flags & BIO_ERROR)) 1488 isc->trim_stats.errs++; 1489 isc->trim_stats.out++; 1490 isc->trim_stats.pending--; 1491 } else if (bp->bio_cmd != BIO_FLUSH) { 1492 if (iosched_debug) 1493 printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd); 1494 } 1495 1496 if (!(bp->bio_flags & BIO_ERROR)) 1497 cam_iosched_io_metric_update(isc, 1498 cam_iosched_sbintime_t(done_ccb->ccb_h.qos.periph_data), 1499 bp->bio_cmd, bp->bio_bcount); 1500 #endif 1501 return retval; 1502 } 1503 1504 /* 1505 * Tell the io scheduler that you've pushed a trim down into the sim. 1506 * This also tells the I/O scheduler not to push any more trims down, so 1507 * some periphs do not call it if they can cope with multiple trims in flight. 1508 */ 1509 void 1510 cam_iosched_submit_trim(struct cam_iosched_softc *isc) 1511 { 1512 1513 isc->flags |= CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1514 } 1515 1516 /* 1517 * Change the sorting policy hint for I/O transactions for this device. 1518 */ 1519 void 1520 cam_iosched_set_sort_queue(struct cam_iosched_softc *isc, int val) 1521 { 1522 1523 isc->sort_io_queue = val; 1524 } 1525 1526 int 1527 cam_iosched_has_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1528 { 1529 return isc->flags & flags; 1530 } 1531 1532 void 1533 cam_iosched_set_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1534 { 1535 isc->flags |= flags; 1536 } 1537 1538 void 1539 cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1540 { 1541 isc->flags &= ~flags; 1542 } 1543 1544 #ifdef CAM_IOSCHED_DYNAMIC 1545 /* 1546 * After the method presented in Jack Crenshaw's 1998 article "Integer 1547 * Square Roots," reprinted at 1548 * http://www.embedded.com/electronics-blogs/programmer-s-toolbox/4219659/Integer-Square-Roots 1549 * and well worth the read. Briefly, we find the power of 4 that's the 1550 * largest smaller than val. We then check each smaller power of 4 to 1551 * see if val is still bigger. The right shifts at each step divide 1552 * the result by 2 which after successive application winds up 1553 * accumulating the right answer. It could also have been accumulated 1554 * using a separate root counter, but this code is smaller and faster 1555 * than that method. This method is also integer size invariant. 1556 * It returns floor(sqrt((float)val)), or the largest integer less than 1557 * or equal to the square root. 1558 */ 1559 static uint64_t 1560 isqrt64(uint64_t val) 1561 { 1562 uint64_t res = 0; 1563 uint64_t bit = 1ULL << (sizeof(uint64_t) * NBBY - 2); 1564 1565 /* 1566 * Find the largest power of 4 smaller than val. 1567 */ 1568 while (bit > val) 1569 bit >>= 2; 1570 1571 /* 1572 * Accumulate the answer, one bit at a time (we keep moving 1573 * them over since 2 is the square root of 4 and we test 1574 * powers of 4). We accumulate where we find the bit, but 1575 * the successive shifts land the bit in the right place 1576 * by the end. 1577 */ 1578 while (bit != 0) { 1579 if (val >= res + bit) { 1580 val -= res + bit; 1581 res = (res >> 1) + bit; 1582 } else 1583 res >>= 1; 1584 bit >>= 2; 1585 } 1586 1587 return res; 1588 } 1589 1590 static sbintime_t latencies[LAT_BUCKETS - 1] = { 1591 SBT_1MS << 0, 1592 SBT_1MS << 1, 1593 SBT_1MS << 2, 1594 SBT_1MS << 3, 1595 SBT_1MS << 4, 1596 SBT_1MS << 5, 1597 SBT_1MS << 6, 1598 SBT_1MS << 7, 1599 SBT_1MS << 8, 1600 SBT_1MS << 9, 1601 SBT_1MS << 10, 1602 SBT_1MS << 11, 1603 SBT_1MS << 12, 1604 SBT_1MS << 13 /* 8.192s */ 1605 }; 1606 1607 static void 1608 cam_iosched_update(struct iop_stats *iop, sbintime_t sim_latency) 1609 { 1610 sbintime_t y, deltasq, delta; 1611 int i; 1612 1613 /* 1614 * Keep counts for latency. We do it by power of two buckets. 1615 * This helps us spot outlier behavior obscured by averages. 1616 */ 1617 for (i = 0; i < LAT_BUCKETS - 1; i++) { 1618 if (sim_latency < latencies[i]) { 1619 iop->latencies[i]++; 1620 break; 1621 } 1622 } 1623 if (i == LAT_BUCKETS - 1) 1624 iop->latencies[i]++; /* Put all > 1024ms values into the last bucket. */ 1625 1626 /* 1627 * Classic exponentially decaying average with a tiny alpha 1628 * (2 ^ -alpha_bits). For more info see the NIST statistical 1629 * handbook. 1630 * 1631 * ema_t = y_t * alpha + ema_t-1 * (1 - alpha) [nist] 1632 * ema_t = y_t * alpha + ema_t-1 - alpha * ema_t-1 1633 * ema_t = alpha * y_t - alpha * ema_t-1 + ema_t-1 1634 * alpha = 1 / (1 << alpha_bits) 1635 * sub e == ema_t-1, b == 1/alpha (== 1 << alpha_bits), d == y_t - ema_t-1 1636 * = y_t/b - e/b + be/b 1637 * = (y_t - e + be) / b 1638 * = (e + d) / b 1639 * 1640 * Since alpha is a power of two, we can compute this w/o any mult or 1641 * division. 1642 * 1643 * Variance can also be computed. Usually, it would be expressed as follows: 1644 * diff_t = y_t - ema_t-1 1645 * emvar_t = (1 - alpha) * (emavar_t-1 + diff_t^2 * alpha) 1646 * = emavar_t-1 - alpha * emavar_t-1 + delta_t^2 * alpha - (delta_t * alpha)^2 1647 * sub b == 1/alpha (== 1 << alpha_bits), e == emavar_t-1, d = delta_t^2 1648 * = e - e/b + dd/b + dd/bb 1649 * = (bbe - be + bdd + dd) / bb 1650 * = (bbe + b(dd-e) + dd) / bb (which is expanded below bb = 1<<(2*alpha_bits)) 1651 */ 1652 /* 1653 * XXX possible numeric issues 1654 * o We assume right shifted integers do the right thing, since that's 1655 * implementation defined. You can change the right shifts to / (1LL << alpha). 1656 * o alpha_bits = 9 gives ema ceiling of 23 bits of seconds for ema and 14 bits 1657 * for emvar. This puts a ceiling of 13 bits on alpha since we need a 1658 * few tens of seconds of representation. 1659 * o We mitigate alpha issues by never setting it too high. 1660 */ 1661 y = sim_latency; 1662 delta = (y - iop->ema); /* d */ 1663 iop->ema = ((iop->ema << alpha_bits) + delta) >> alpha_bits; 1664 1665 /* 1666 * Were we to naively plow ahead at this point, we wind up with many numerical 1667 * issues making any SD > ~3ms unreliable. So, we shift right by 12. This leaves 1668 * us with microsecond level precision in the input, so the same in the 1669 * output. It means we can't overflow deltasq unless delta > 4k seconds. It 1670 * also means that emvar can be up 46 bits 40 of which are fraction, which 1671 * gives us a way to measure up to ~8s in the SD before the computation goes 1672 * unstable. Even the worst hard disk rarely has > 1s service time in the 1673 * drive. It does mean we have to shift left 12 bits after taking the 1674 * square root to compute the actual standard deviation estimate. This loss of 1675 * precision is preferable to needing int128 types to work. The above numbers 1676 * assume alpha=9. 10 or 11 are ok, but we start to run into issues at 12, 1677 * so 12 or 13 is OK for EMA, EMVAR and SD will be wrong in those cases. 1678 */ 1679 delta >>= 12; 1680 deltasq = delta * delta; /* dd */ 1681 iop->emvar = ((iop->emvar << (2 * alpha_bits)) + /* bbe */ 1682 ((deltasq - iop->emvar) << alpha_bits) + /* b(dd-e) */ 1683 deltasq) /* dd */ 1684 >> (2 * alpha_bits); /* div bb */ 1685 iop->sd = (sbintime_t)isqrt64((uint64_t)iop->emvar) << 12; 1686 } 1687 1688 static void 1689 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 1690 sbintime_t sim_latency, int cmd, size_t size) 1691 { 1692 /* xxx Do we need to scale based on the size of the I/O ? */ 1693 switch (cmd) { 1694 case BIO_READ: 1695 cam_iosched_update(&isc->read_stats, sim_latency); 1696 break; 1697 case BIO_WRITE: 1698 cam_iosched_update(&isc->write_stats, sim_latency); 1699 break; 1700 case BIO_DELETE: 1701 cam_iosched_update(&isc->trim_stats, sim_latency); 1702 break; 1703 default: 1704 break; 1705 } 1706 } 1707 1708 #ifdef DDB 1709 static int biolen(struct bio_queue_head *bq) 1710 { 1711 int i = 0; 1712 struct bio *bp; 1713 1714 TAILQ_FOREACH(bp, &bq->queue, bio_queue) { 1715 i++; 1716 } 1717 return i; 1718 } 1719 1720 /* 1721 * Show the internal state of the I/O scheduler. 1722 */ 1723 DB_SHOW_COMMAND(iosched, cam_iosched_db_show) 1724 { 1725 struct cam_iosched_softc *isc; 1726 1727 if (!have_addr) { 1728 db_printf("Need addr\n"); 1729 return; 1730 } 1731 isc = (struct cam_iosched_softc *)addr; 1732 db_printf("pending_reads: %d\n", isc->read_stats.pending); 1733 db_printf("min_reads: %d\n", isc->read_stats.min); 1734 db_printf("max_reads: %d\n", isc->read_stats.max); 1735 db_printf("reads: %d\n", isc->read_stats.total); 1736 db_printf("in_reads: %d\n", isc->read_stats.in); 1737 db_printf("out_reads: %d\n", isc->read_stats.out); 1738 db_printf("queued_reads: %d\n", isc->read_stats.queued); 1739 db_printf("Current Q len %d\n", biolen(&isc->bio_queue)); 1740 db_printf("pending_writes: %d\n", isc->write_stats.pending); 1741 db_printf("min_writes: %d\n", isc->write_stats.min); 1742 db_printf("max_writes: %d\n", isc->write_stats.max); 1743 db_printf("writes: %d\n", isc->write_stats.total); 1744 db_printf("in_writes: %d\n", isc->write_stats.in); 1745 db_printf("out_writes: %d\n", isc->write_stats.out); 1746 db_printf("queued_writes: %d\n", isc->write_stats.queued); 1747 db_printf("Current Q len %d\n", biolen(&isc->write_queue)); 1748 db_printf("pending_trims: %d\n", isc->trim_stats.pending); 1749 db_printf("min_trims: %d\n", isc->trim_stats.min); 1750 db_printf("max_trims: %d\n", isc->trim_stats.max); 1751 db_printf("trims: %d\n", isc->trim_stats.total); 1752 db_printf("in_trims: %d\n", isc->trim_stats.in); 1753 db_printf("out_trims: %d\n", isc->trim_stats.out); 1754 db_printf("queued_trims: %d\n", isc->trim_stats.queued); 1755 db_printf("Current Q len %d\n", biolen(&isc->trim_queue)); 1756 db_printf("read_bias: %d\n", isc->read_bias); 1757 db_printf("current_read_bias: %d\n", isc->current_read_bias); 1758 db_printf("Trim active? %s\n", 1759 (isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) ? "yes" : "no"); 1760 } 1761 #endif 1762 #endif 1763