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