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