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/sysctl.h> 46 47 #include <cam/cam.h> 48 #include <cam/cam_ccb.h> 49 #include <cam/cam_periph.h> 50 #include <cam/cam_xpt_periph.h> 51 #include <cam/cam_iosched.h> 52 53 #include <ddb/ddb.h> 54 55 static MALLOC_DEFINE(M_CAMSCHED, "CAM I/O Scheduler", 56 "CAM I/O Scheduler buffers"); 57 58 /* 59 * Default I/O scheduler for FreeBSD. This implementation is just a thin-vineer 60 * over the bioq_* interface, with notions of separate calls for normal I/O and 61 * for trims. 62 * 63 * When CAM_IOSCHED_DYNAMIC is defined, the scheduler is enhanced to dynamically 64 * steer the rate of one type of traffic to help other types of traffic (eg 65 * limit writes when read latency deteriorates on SSDs). 66 */ 67 68 #ifdef CAM_IOSCHED_DYNAMIC 69 70 static int do_dynamic_iosched = 1; 71 TUNABLE_INT("kern.cam.do_dynamic_iosched", &do_dynamic_iosched); 72 SYSCTL_INT(_kern_cam, OID_AUTO, do_dynamic_iosched, CTLFLAG_RD, 73 &do_dynamic_iosched, 1, 74 "Enable Dynamic I/O scheduler optimizations."); 75 76 static int alpha_bits = 9; 77 TUNABLE_INT("kern.cam.iosched_alpha_bits", &alpha_bits); 78 SYSCTL_INT(_kern_cam, OID_AUTO, iosched_alpha_bits, CTLFLAG_RW, 79 &alpha_bits, 1, 80 "Bits in EMA's alpha."); 81 82 83 84 struct iop_stats; 85 struct cam_iosched_softc; 86 87 int iosched_debug = 0; 88 89 typedef enum { 90 none = 0, /* No limits */ 91 queue_depth, /* Limit how many ops we queue to SIM */ 92 iops, /* Limit # of IOPS to the drive */ 93 bandwidth, /* Limit bandwidth to the drive */ 94 limiter_max 95 } io_limiter; 96 97 static const char *cam_iosched_limiter_names[] = 98 { "none", "queue_depth", "iops", "bandwidth" }; 99 100 /* 101 * Called to initialize the bits of the iop_stats structure relevant to the 102 * limiter. Called just after the limiter is set. 103 */ 104 typedef int l_init_t(struct iop_stats *); 105 106 /* 107 * Called every tick. 108 */ 109 typedef int l_tick_t(struct iop_stats *); 110 111 /* 112 * Called to see if the limiter thinks this IOP can be allowed to 113 * proceed. If so, the limiter assumes that the while IOP proceeded 114 * and makes any accounting of it that's needed. 115 */ 116 typedef int l_iop_t(struct iop_stats *, struct bio *); 117 118 /* 119 * Called when an I/O completes so the limiter can updates its 120 * accounting. Pending I/Os may complete in any order (even when 121 * sent to the hardware at the same time), so the limiter may not 122 * make any assumptions other than this I/O has completed. If it 123 * returns 1, then xpt_schedule() needs to be called again. 124 */ 125 typedef int l_iodone_t(struct iop_stats *, struct bio *); 126 127 static l_iop_t cam_iosched_qd_iop; 128 static l_iop_t cam_iosched_qd_caniop; 129 static l_iodone_t cam_iosched_qd_iodone; 130 131 static l_init_t cam_iosched_iops_init; 132 static l_tick_t cam_iosched_iops_tick; 133 static l_iop_t cam_iosched_iops_caniop; 134 static l_iop_t cam_iosched_iops_iop; 135 136 static l_init_t cam_iosched_bw_init; 137 static l_tick_t cam_iosched_bw_tick; 138 static l_iop_t cam_iosched_bw_caniop; 139 static l_iop_t cam_iosched_bw_iop; 140 141 struct limswitch 142 { 143 l_init_t *l_init; 144 l_tick_t *l_tick; 145 l_iop_t *l_iop; 146 l_iop_t *l_caniop; 147 l_iodone_t *l_iodone; 148 } limsw[] = 149 { 150 { /* none */ 151 .l_init = NULL, 152 .l_tick = NULL, 153 .l_iop = NULL, 154 .l_iodone= NULL, 155 }, 156 { /* queue_depth */ 157 .l_init = NULL, 158 .l_tick = NULL, 159 .l_caniop = cam_iosched_qd_caniop, 160 .l_iop = cam_iosched_qd_iop, 161 .l_iodone= cam_iosched_qd_iodone, 162 }, 163 { /* iops */ 164 .l_init = cam_iosched_iops_init, 165 .l_tick = cam_iosched_iops_tick, 166 .l_caniop = cam_iosched_iops_caniop, 167 .l_iop = cam_iosched_iops_iop, 168 .l_iodone= NULL, 169 }, 170 { /* bandwidth */ 171 .l_init = cam_iosched_bw_init, 172 .l_tick = cam_iosched_bw_tick, 173 .l_caniop = cam_iosched_bw_caniop, 174 .l_iop = cam_iosched_bw_iop, 175 .l_iodone= NULL, 176 }, 177 }; 178 179 struct iop_stats 180 { 181 /* 182 * sysctl state for this subnode. 183 */ 184 struct sysctl_ctx_list sysctl_ctx; 185 struct sysctl_oid *sysctl_tree; 186 187 /* 188 * Information about the current rate limiters, if any 189 */ 190 io_limiter limiter; /* How are I/Os being limited */ 191 int min; /* Low range of limit */ 192 int max; /* High range of limit */ 193 int current; /* Current rate limiter */ 194 int l_value1; /* per-limiter scratch value 1. */ 195 int l_value2; /* per-limiter scratch value 2. */ 196 197 198 /* 199 * Debug information about counts of I/Os that have gone through the 200 * scheduler. 201 */ 202 int pending; /* I/Os pending in the hardware */ 203 int queued; /* number currently in the queue */ 204 int total; /* Total for all time -- wraps */ 205 int in; /* number queued all time -- wraps */ 206 int out; /* number completed all time -- wraps */ 207 208 /* 209 * Statistics on different bits of the process. 210 */ 211 /* Exp Moving Average, alpha = 1 / (1 << alpha_bits) */ 212 sbintime_t ema; 213 sbintime_t emss; /* Exp Moving sum of the squares */ 214 sbintime_t sd; /* Last computed sd */ 215 216 struct cam_iosched_softc *softc; 217 }; 218 219 220 typedef enum { 221 set_max = 0, /* current = max */ 222 read_latency, /* Steer read latency by throttling writes */ 223 cl_max /* Keep last */ 224 } control_type; 225 226 static const char *cam_iosched_control_type_names[] = 227 { "set_max", "read_latency" }; 228 229 struct control_loop 230 { 231 /* 232 * sysctl state for this subnode. 233 */ 234 struct sysctl_ctx_list sysctl_ctx; 235 struct sysctl_oid *sysctl_tree; 236 237 sbintime_t next_steer; /* Time of next steer */ 238 sbintime_t steer_interval; /* How often do we steer? */ 239 sbintime_t lolat; 240 sbintime_t hilat; 241 int alpha; 242 control_type type; /* What type of control? */ 243 int last_count; /* Last I/O count */ 244 245 struct cam_iosched_softc *softc; 246 }; 247 248 #endif 249 250 struct cam_iosched_softc 251 { 252 struct bio_queue_head bio_queue; 253 struct bio_queue_head trim_queue; 254 /* scheduler flags < 16, user flags >= 16 */ 255 uint32_t flags; 256 int sort_io_queue; 257 #ifdef CAM_IOSCHED_DYNAMIC 258 int read_bias; /* Read bias setting */ 259 int current_read_bias; /* Current read bias state */ 260 int total_ticks; 261 262 struct bio_queue_head write_queue; 263 struct iop_stats read_stats, write_stats, trim_stats; 264 struct sysctl_ctx_list sysctl_ctx; 265 struct sysctl_oid *sysctl_tree; 266 267 int quanta; /* Number of quanta per second */ 268 struct callout ticker; /* Callout for our quota system */ 269 struct cam_periph *periph; /* cam periph associated with this device */ 270 uint32_t this_frac; /* Fraction of a second (1024ths) for this tick */ 271 sbintime_t last_time; /* Last time we ticked */ 272 struct control_loop cl; 273 #endif 274 }; 275 276 #ifdef CAM_IOSCHED_DYNAMIC 277 /* 278 * helper functions to call the limsw functions. 279 */ 280 static int 281 cam_iosched_limiter_init(struct iop_stats *ios) 282 { 283 int lim = ios->limiter; 284 285 /* maybe this should be a kassert */ 286 if (lim < none || lim >= limiter_max) 287 return EINVAL; 288 289 if (limsw[lim].l_init) 290 return limsw[lim].l_init(ios); 291 292 return 0; 293 } 294 295 static int 296 cam_iosched_limiter_tick(struct iop_stats *ios) 297 { 298 int lim = ios->limiter; 299 300 /* maybe this should be a kassert */ 301 if (lim < none || lim >= limiter_max) 302 return EINVAL; 303 304 if (limsw[lim].l_tick) 305 return limsw[lim].l_tick(ios); 306 307 return 0; 308 } 309 310 static int 311 cam_iosched_limiter_iop(struct iop_stats *ios, struct bio *bp) 312 { 313 int lim = ios->limiter; 314 315 /* maybe this should be a kassert */ 316 if (lim < none || lim >= limiter_max) 317 return EINVAL; 318 319 if (limsw[lim].l_iop) 320 return limsw[lim].l_iop(ios, bp); 321 322 return 0; 323 } 324 325 static int 326 cam_iosched_limiter_caniop(struct iop_stats *ios, struct bio *bp) 327 { 328 int lim = ios->limiter; 329 330 /* maybe this should be a kassert */ 331 if (lim < none || lim >= limiter_max) 332 return EINVAL; 333 334 if (limsw[lim].l_caniop) 335 return limsw[lim].l_caniop(ios, bp); 336 337 return 0; 338 } 339 340 static int 341 cam_iosched_limiter_iodone(struct iop_stats *ios, struct bio *bp) 342 { 343 int lim = ios->limiter; 344 345 /* maybe this should be a kassert */ 346 if (lim < none || lim >= limiter_max) 347 return 0; 348 349 if (limsw[lim].l_iodone) 350 return limsw[lim].l_iodone(ios, bp); 351 352 return 0; 353 } 354 355 /* 356 * Functions to implement the different kinds of limiters 357 */ 358 359 static int 360 cam_iosched_qd_iop(struct iop_stats *ios, struct bio *bp) 361 { 362 363 if (ios->current <= 0 || ios->pending < ios->current) 364 return 0; 365 366 return EAGAIN; 367 } 368 369 static int 370 cam_iosched_qd_caniop(struct iop_stats *ios, struct bio *bp) 371 { 372 373 if (ios->current <= 0 || ios->pending < ios->current) 374 return 0; 375 376 return EAGAIN; 377 } 378 379 static int 380 cam_iosched_qd_iodone(struct iop_stats *ios, struct bio *bp) 381 { 382 383 if (ios->current <= 0 || ios->pending != ios->current) 384 return 0; 385 386 return 1; 387 } 388 389 static int 390 cam_iosched_iops_init(struct iop_stats *ios) 391 { 392 393 ios->l_value1 = ios->current / ios->softc->quanta; 394 if (ios->l_value1 <= 0) 395 ios->l_value1 = 1; 396 397 return 0; 398 } 399 400 static int 401 cam_iosched_iops_tick(struct iop_stats *ios) 402 { 403 404 ios->l_value1 = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16); 405 if (ios->l_value1 <= 0) 406 ios->l_value1 = 1; 407 408 return 0; 409 } 410 411 static int 412 cam_iosched_iops_caniop(struct iop_stats *ios, struct bio *bp) 413 { 414 415 /* 416 * So if we have any more IOPs left, allow it, 417 * otherwise wait. 418 */ 419 if (ios->l_value1 <= 0) 420 return EAGAIN; 421 return 0; 422 } 423 424 static int 425 cam_iosched_iops_iop(struct iop_stats *ios, struct bio *bp) 426 { 427 int rv; 428 429 rv = cam_iosched_limiter_caniop(ios, bp); 430 if (rv == 0) 431 ios->l_value1--; 432 433 return rv; 434 } 435 436 static int 437 cam_iosched_bw_init(struct iop_stats *ios) 438 { 439 440 /* ios->current is in kB/s, so scale to bytes */ 441 ios->l_value1 = ios->current * 1000 / ios->softc->quanta; 442 443 return 0; 444 } 445 446 static int 447 cam_iosched_bw_tick(struct iop_stats *ios) 448 { 449 int bw; 450 451 /* 452 * If we're in the hole for available quota from 453 * the last time, then add the quantum for this. 454 * If we have any left over from last quantum, 455 * then too bad, that's lost. Also, ios->current 456 * is in kB/s, so scale. 457 * 458 * We also allow up to 4 quanta of credits to 459 * accumulate to deal with burstiness. 4 is extremely 460 * arbitrary. 461 */ 462 bw = (int)((ios->current * 1000ull * (uint64_t)ios->softc->this_frac) >> 16); 463 if (ios->l_value1 < bw * 4) 464 ios->l_value1 += bw; 465 466 return 0; 467 } 468 469 static int 470 cam_iosched_bw_caniop(struct iop_stats *ios, struct bio *bp) 471 { 472 /* 473 * So if we have any more bw quota left, allow it, 474 * otherwise wait. Not, we'll go negative and that's 475 * OK. We'll just get a lettle less next quota. 476 * 477 * Note on going negative: that allows us to process 478 * requests in order better, since we won't allow 479 * shorter reads to get around the long one that we 480 * don't have the quota to do just yet. It also prevents 481 * starvation by being a little more permissive about 482 * what we let through this quantum (to prevent the 483 * starvation), at the cost of getting a little less 484 * next quantum. 485 */ 486 if (ios->l_value1 <= 0) 487 return EAGAIN; 488 489 490 return 0; 491 } 492 493 static int 494 cam_iosched_bw_iop(struct iop_stats *ios, struct bio *bp) 495 { 496 int rv; 497 498 rv = cam_iosched_limiter_caniop(ios, bp); 499 if (rv == 0) 500 ios->l_value1 -= bp->bio_length; 501 502 return rv; 503 } 504 505 static void cam_iosched_cl_maybe_steer(struct control_loop *clp); 506 507 static void 508 cam_iosched_ticker(void *arg) 509 { 510 struct cam_iosched_softc *isc = arg; 511 sbintime_t now, delta; 512 513 callout_reset(&isc->ticker, hz / isc->quanta - 1, cam_iosched_ticker, isc); 514 515 now = sbinuptime(); 516 delta = now - isc->last_time; 517 isc->this_frac = (uint32_t)delta >> 16; /* Note: discards seconds -- should be 0 harmless if not */ 518 isc->last_time = now; 519 520 cam_iosched_cl_maybe_steer(&isc->cl); 521 522 cam_iosched_limiter_tick(&isc->read_stats); 523 cam_iosched_limiter_tick(&isc->write_stats); 524 cam_iosched_limiter_tick(&isc->trim_stats); 525 526 cam_iosched_schedule(isc, isc->periph); 527 528 isc->total_ticks++; 529 } 530 531 532 static void 533 cam_iosched_cl_init(struct control_loop *clp, struct cam_iosched_softc *isc) 534 { 535 536 clp->next_steer = sbinuptime(); 537 clp->softc = isc; 538 clp->steer_interval = SBT_1S * 5; /* Let's start out steering every 5s */ 539 clp->lolat = 5 * SBT_1MS; 540 clp->hilat = 15 * SBT_1MS; 541 clp->alpha = 20; /* Alpha == gain. 20 = .2 */ 542 clp->type = set_max; 543 } 544 545 static void 546 cam_iosched_cl_maybe_steer(struct control_loop *clp) 547 { 548 struct cam_iosched_softc *isc; 549 sbintime_t now, lat; 550 int old; 551 552 isc = clp->softc; 553 now = isc->last_time; 554 if (now < clp->next_steer) 555 return; 556 557 clp->next_steer = now + clp->steer_interval; 558 switch (clp->type) { 559 case set_max: 560 if (isc->write_stats.current != isc->write_stats.max) 561 printf("Steering write from %d kBps to %d kBps\n", 562 isc->write_stats.current, isc->write_stats.max); 563 isc->read_stats.current = isc->read_stats.max; 564 isc->write_stats.current = isc->write_stats.max; 565 isc->trim_stats.current = isc->trim_stats.max; 566 break; 567 case read_latency: 568 old = isc->write_stats.current; 569 lat = isc->read_stats.ema; 570 /* 571 * Simple PLL-like engine. Since we're steering to a range for 572 * the SP (set point) that makes things a little more 573 * complicated. In addition, we're not directly controlling our 574 * PV (process variable), the read latency, but instead are 575 * manipulating the write bandwidth limit for our MV 576 * (manipulation variable), analysis of this code gets a bit 577 * messy. Also, the MV is a very noisy control surface for read 578 * latency since it is affected by many hidden processes inside 579 * the device which change how responsive read latency will be 580 * in reaction to changes in write bandwidth. Unlike the classic 581 * boiler control PLL. this may result in over-steering while 582 * the SSD takes its time to react to the new, lower load. This 583 * is why we use a relatively low alpha of between .1 and .25 to 584 * compensate for this effect. At .1, it takes ~22 steering 585 * intervals to back off by a factor of 10. At .2 it only takes 586 * ~10. At .25 it only takes ~8. However some preliminary data 587 * from the SSD drives suggests a reasponse time in 10's of 588 * seconds before latency drops regardless of the new write 589 * rate. Careful observation will be reqiured to tune this 590 * effectively. 591 * 592 * Also, when there's no read traffic, we jack up the write 593 * limit too regardless of the last read latency. 10 is 594 * somewhat arbitrary. 595 */ 596 if (lat < clp->lolat || isc->read_stats.total - clp->last_count < 10) 597 isc->write_stats.current = isc->write_stats.current * 598 (100 + clp->alpha) / 100; /* Scale up */ 599 else if (lat > clp->hilat) 600 isc->write_stats.current = isc->write_stats.current * 601 (100 - clp->alpha) / 100; /* Scale down */ 602 clp->last_count = isc->read_stats.total; 603 604 /* 605 * Even if we don't steer, per se, enforce the min/max limits as 606 * those may have changed. 607 */ 608 if (isc->write_stats.current < isc->write_stats.min) 609 isc->write_stats.current = isc->write_stats.min; 610 if (isc->write_stats.current > isc->write_stats.max) 611 isc->write_stats.current = isc->write_stats.max; 612 if (old != isc->write_stats.current && iosched_debug) 613 printf("Steering write from %d kBps to %d kBps due to latency of %jdms\n", 614 old, isc->write_stats.current, 615 (uintmax_t)((uint64_t)1000000 * (uint32_t)lat) >> 32); 616 break; 617 case cl_max: 618 break; 619 } 620 } 621 #endif 622 623 /* Trim or similar currently pending completion */ 624 #define CAM_IOSCHED_FLAG_TRIM_ACTIVE (1ul << 0) 625 /* Callout active, and needs to be torn down */ 626 #define CAM_IOSCHED_FLAG_CALLOUT_ACTIVE (1ul << 1) 627 628 /* Periph drivers set these flags to indicate work */ 629 #define CAM_IOSCHED_FLAG_WORK_FLAGS ((0xffffu) << 16) 630 631 #ifdef CAM_IOSCHED_DYNAMIC 632 static void 633 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 634 sbintime_t sim_latency, int cmd, size_t size); 635 #endif 636 637 static inline int 638 cam_iosched_has_flagged_work(struct cam_iosched_softc *isc) 639 { 640 return !!(isc->flags & CAM_IOSCHED_FLAG_WORK_FLAGS); 641 } 642 643 static inline int 644 cam_iosched_has_io(struct cam_iosched_softc *isc) 645 { 646 #ifdef CAM_IOSCHED_DYNAMIC 647 if (do_dynamic_iosched) { 648 struct bio *rbp = bioq_first(&isc->bio_queue); 649 struct bio *wbp = bioq_first(&isc->write_queue); 650 int can_write = wbp != NULL && 651 cam_iosched_limiter_caniop(&isc->write_stats, wbp) == 0; 652 int can_read = rbp != NULL && 653 cam_iosched_limiter_caniop(&isc->read_stats, rbp) == 0; 654 if (iosched_debug > 2) { 655 printf("can write %d: pending_writes %d max_writes %d\n", can_write, isc->write_stats.pending, isc->write_stats.max); 656 printf("can read %d: read_stats.pending %d max_reads %d\n", can_read, isc->read_stats.pending, isc->read_stats.max); 657 printf("Queued reads %d writes %d\n", isc->read_stats.queued, isc->write_stats.queued); 658 } 659 return can_read || can_write; 660 } 661 #endif 662 return bioq_first(&isc->bio_queue) != NULL; 663 } 664 665 static inline int 666 cam_iosched_has_more_trim(struct cam_iosched_softc *isc) 667 { 668 return !(isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) && 669 bioq_first(&isc->trim_queue); 670 } 671 672 #define cam_iosched_sort_queue(isc) ((isc)->sort_io_queue >= 0 ? \ 673 (isc)->sort_io_queue : cam_sort_io_queues) 674 675 676 static inline int 677 cam_iosched_has_work(struct cam_iosched_softc *isc) 678 { 679 #ifdef CAM_IOSCHED_DYNAMIC 680 if (iosched_debug > 2) 681 printf("has work: %d %d %d\n", cam_iosched_has_io(isc), 682 cam_iosched_has_more_trim(isc), 683 cam_iosched_has_flagged_work(isc)); 684 #endif 685 686 return cam_iosched_has_io(isc) || 687 cam_iosched_has_more_trim(isc) || 688 cam_iosched_has_flagged_work(isc); 689 } 690 691 #ifdef CAM_IOSCHED_DYNAMIC 692 static void 693 cam_iosched_iop_stats_init(struct cam_iosched_softc *isc, struct iop_stats *ios) 694 { 695 696 ios->limiter = none; 697 cam_iosched_limiter_init(ios); 698 ios->in = 0; 699 ios->max = 300000; 700 ios->min = 1; 701 ios->out = 0; 702 ios->pending = 0; 703 ios->queued = 0; 704 ios->total = 0; 705 ios->ema = 0; 706 ios->emss = 0; 707 ios->sd = 0; 708 ios->softc = isc; 709 } 710 711 static int 712 cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS) 713 { 714 char buf[16]; 715 struct iop_stats *ios; 716 struct cam_iosched_softc *isc; 717 int value, i, error, cantick; 718 const char *p; 719 720 ios = arg1; 721 isc = ios->softc; 722 value = ios->limiter; 723 if (value < none || value >= limiter_max) 724 p = "UNKNOWN"; 725 else 726 p = cam_iosched_limiter_names[value]; 727 728 strlcpy(buf, p, sizeof(buf)); 729 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 730 if (error != 0 || req->newptr == NULL) 731 return error; 732 733 cam_periph_lock(isc->periph); 734 735 for (i = none; i < limiter_max; i++) { 736 if (strcmp(buf, cam_iosched_limiter_names[i]) != 0) 737 continue; 738 ios->limiter = i; 739 error = cam_iosched_limiter_init(ios); 740 if (error != 0) { 741 ios->limiter = value; 742 cam_periph_unlock(isc->periph); 743 return error; 744 } 745 cantick = !!limsw[isc->read_stats.limiter].l_tick + 746 !!limsw[isc->write_stats.limiter].l_tick + 747 !!limsw[isc->trim_stats.limiter].l_tick + 748 1; /* Control loop requires it */ 749 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) { 750 if (cantick == 0) { 751 callout_stop(&isc->ticker); 752 isc->flags &= ~CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 753 } 754 } else { 755 if (cantick != 0) { 756 callout_reset(&isc->ticker, hz / isc->quanta - 1, cam_iosched_ticker, isc); 757 isc->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 758 } 759 } 760 761 cam_periph_unlock(isc->periph); 762 return 0; 763 } 764 765 cam_periph_unlock(isc->periph); 766 return EINVAL; 767 } 768 769 static int 770 cam_iosched_control_type_sysctl(SYSCTL_HANDLER_ARGS) 771 { 772 char buf[16]; 773 struct control_loop *clp; 774 struct cam_iosched_softc *isc; 775 int value, i, error; 776 const char *p; 777 778 clp = arg1; 779 isc = clp->softc; 780 value = clp->type; 781 if (value < none || value >= cl_max) 782 p = "UNKNOWN"; 783 else 784 p = cam_iosched_control_type_names[value]; 785 786 strlcpy(buf, p, sizeof(buf)); 787 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 788 if (error != 0 || req->newptr == NULL) 789 return error; 790 791 for (i = set_max; i < cl_max; i++) { 792 if (strcmp(buf, cam_iosched_control_type_names[i]) != 0) 793 continue; 794 cam_periph_lock(isc->periph); 795 clp->type = i; 796 cam_periph_unlock(isc->periph); 797 return 0; 798 } 799 800 return EINVAL; 801 } 802 803 static int 804 cam_iosched_sbintime_sysctl(SYSCTL_HANDLER_ARGS) 805 { 806 char buf[16]; 807 sbintime_t value; 808 int error; 809 uint64_t us; 810 811 value = *(sbintime_t *)arg1; 812 us = (uint64_t)value / SBT_1US; 813 snprintf(buf, sizeof(buf), "%ju", (intmax_t)us); 814 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 815 if (error != 0 || req->newptr == NULL) 816 return error; 817 us = strtoul(buf, NULL, 10); 818 if (us == 0) 819 return EINVAL; 820 *(sbintime_t *)arg1 = us * SBT_1US; 821 return 0; 822 } 823 824 static void 825 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct iop_stats *ios, char *name) 826 { 827 struct sysctl_oid_list *n; 828 struct sysctl_ctx_list *ctx; 829 830 ios->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 831 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, name, 832 CTLFLAG_RD, 0, name); 833 n = SYSCTL_CHILDREN(ios->sysctl_tree); 834 ctx = &ios->sysctl_ctx; 835 836 SYSCTL_ADD_UQUAD(ctx, n, 837 OID_AUTO, "ema", CTLFLAG_RD, 838 &ios->ema, 839 "Fast Exponentially Weighted Moving Average"); 840 SYSCTL_ADD_UQUAD(ctx, n, 841 OID_AUTO, "emss", CTLFLAG_RD, 842 &ios->emss, 843 "Fast Exponentially Weighted Moving Sum of Squares (maybe wrong)"); 844 SYSCTL_ADD_UQUAD(ctx, n, 845 OID_AUTO, "sd", CTLFLAG_RD, 846 &ios->sd, 847 "Estimated SD for fast ema (may be wrong)"); 848 849 SYSCTL_ADD_INT(ctx, n, 850 OID_AUTO, "pending", CTLFLAG_RD, 851 &ios->pending, 0, 852 "Instantaneous # of pending transactions"); 853 SYSCTL_ADD_INT(ctx, n, 854 OID_AUTO, "count", CTLFLAG_RD, 855 &ios->total, 0, 856 "# of transactions submitted to hardware"); 857 SYSCTL_ADD_INT(ctx, n, 858 OID_AUTO, "queued", CTLFLAG_RD, 859 &ios->queued, 0, 860 "# of transactions in the queue"); 861 SYSCTL_ADD_INT(ctx, n, 862 OID_AUTO, "in", CTLFLAG_RD, 863 &ios->in, 0, 864 "# of transactions queued to driver"); 865 SYSCTL_ADD_INT(ctx, n, 866 OID_AUTO, "out", CTLFLAG_RD, 867 &ios->out, 0, 868 "# of transactions completed"); 869 870 SYSCTL_ADD_PROC(ctx, n, 871 OID_AUTO, "limiter", CTLTYPE_STRING | CTLFLAG_RW, 872 ios, 0, cam_iosched_limiter_sysctl, "A", 873 "Current limiting type."); 874 SYSCTL_ADD_INT(ctx, n, 875 OID_AUTO, "min", CTLFLAG_RW, 876 &ios->min, 0, 877 "min resource"); 878 SYSCTL_ADD_INT(ctx, n, 879 OID_AUTO, "max", CTLFLAG_RW, 880 &ios->max, 0, 881 "max resource"); 882 SYSCTL_ADD_INT(ctx, n, 883 OID_AUTO, "current", CTLFLAG_RW, 884 &ios->current, 0, 885 "current resource"); 886 887 } 888 889 static void 890 cam_iosched_iop_stats_fini(struct iop_stats *ios) 891 { 892 if (ios->sysctl_tree) 893 if (sysctl_ctx_free(&ios->sysctl_ctx) != 0) 894 printf("can't remove iosched sysctl stats context\n"); 895 } 896 897 static void 898 cam_iosched_cl_sysctl_init(struct cam_iosched_softc *isc) 899 { 900 struct sysctl_oid_list *n; 901 struct sysctl_ctx_list *ctx; 902 struct control_loop *clp; 903 904 clp = &isc->cl; 905 clp->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 906 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, "control", 907 CTLFLAG_RD, 0, "Control loop info"); 908 n = SYSCTL_CHILDREN(clp->sysctl_tree); 909 ctx = &clp->sysctl_ctx; 910 911 SYSCTL_ADD_PROC(ctx, n, 912 OID_AUTO, "type", CTLTYPE_STRING | CTLFLAG_RW, 913 clp, 0, cam_iosched_control_type_sysctl, "A", 914 "Control loop algorithm"); 915 SYSCTL_ADD_PROC(ctx, n, 916 OID_AUTO, "steer_interval", CTLTYPE_STRING | CTLFLAG_RW, 917 &clp->steer_interval, 0, cam_iosched_sbintime_sysctl, "A", 918 "How often to steer (in us)"); 919 SYSCTL_ADD_PROC(ctx, n, 920 OID_AUTO, "lolat", CTLTYPE_STRING | CTLFLAG_RW, 921 &clp->lolat, 0, cam_iosched_sbintime_sysctl, "A", 922 "Low water mark for Latency (in us)"); 923 SYSCTL_ADD_PROC(ctx, n, 924 OID_AUTO, "hilat", CTLTYPE_STRING | CTLFLAG_RW, 925 &clp->hilat, 0, cam_iosched_sbintime_sysctl, "A", 926 "Hi water mark for Latency (in us)"); 927 SYSCTL_ADD_INT(ctx, n, 928 OID_AUTO, "alpha", CTLFLAG_RW, 929 &clp->alpha, 0, 930 "Alpha for PLL (x100) aka gain"); 931 } 932 933 static void 934 cam_iosched_cl_sysctl_fini(struct control_loop *clp) 935 { 936 if (clp->sysctl_tree) 937 if (sysctl_ctx_free(&clp->sysctl_ctx) != 0) 938 printf("can't remove iosched sysctl control loop context\n"); 939 } 940 #endif 941 942 /* 943 * Allocate the iosched structure. This also insulates callers from knowing 944 * sizeof struct cam_iosched_softc. 945 */ 946 int 947 cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph) 948 { 949 950 *iscp = malloc(sizeof(**iscp), M_CAMSCHED, M_NOWAIT | M_ZERO); 951 if (*iscp == NULL) 952 return ENOMEM; 953 #ifdef CAM_IOSCHED_DYNAMIC 954 if (iosched_debug) 955 printf("CAM IOSCHEDULER Allocating entry at %p\n", *iscp); 956 #endif 957 (*iscp)->sort_io_queue = -1; 958 bioq_init(&(*iscp)->bio_queue); 959 bioq_init(&(*iscp)->trim_queue); 960 #ifdef CAM_IOSCHED_DYNAMIC 961 if (do_dynamic_iosched) { 962 bioq_init(&(*iscp)->write_queue); 963 (*iscp)->read_bias = 100; 964 (*iscp)->current_read_bias = 100; 965 (*iscp)->quanta = 200; 966 cam_iosched_iop_stats_init(*iscp, &(*iscp)->read_stats); 967 cam_iosched_iop_stats_init(*iscp, &(*iscp)->write_stats); 968 cam_iosched_iop_stats_init(*iscp, &(*iscp)->trim_stats); 969 (*iscp)->trim_stats.max = 1; /* Trims are special: one at a time for now */ 970 (*iscp)->last_time = sbinuptime(); 971 callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0); 972 (*iscp)->periph = periph; 973 cam_iosched_cl_init(&(*iscp)->cl, *iscp); 974 callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta - 1, cam_iosched_ticker, *iscp); 975 (*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 976 } 977 #endif 978 979 return 0; 980 } 981 982 /* 983 * Reclaim all used resources. This assumes that other folks have 984 * drained the requests in the hardware. Maybe an unwise assumption. 985 */ 986 void 987 cam_iosched_fini(struct cam_iosched_softc *isc) 988 { 989 if (isc) { 990 cam_iosched_flush(isc, NULL, ENXIO); 991 #ifdef CAM_IOSCHED_DYNAMIC 992 cam_iosched_iop_stats_fini(&isc->read_stats); 993 cam_iosched_iop_stats_fini(&isc->write_stats); 994 cam_iosched_iop_stats_fini(&isc->trim_stats); 995 cam_iosched_cl_sysctl_fini(&isc->cl); 996 if (isc->sysctl_tree) 997 if (sysctl_ctx_free(&isc->sysctl_ctx) != 0) 998 printf("can't remove iosched sysctl stats context\n"); 999 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) { 1000 callout_drain(&isc->ticker); 1001 isc->flags &= ~ CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1002 } 1003 1004 #endif 1005 free(isc, M_CAMSCHED); 1006 } 1007 } 1008 1009 /* 1010 * After we're sure we're attaching a device, go ahead and add 1011 * hooks for any sysctl we may wish to honor. 1012 */ 1013 void cam_iosched_sysctl_init(struct cam_iosched_softc *isc, 1014 struct sysctl_ctx_list *ctx, struct sysctl_oid *node) 1015 { 1016 #ifdef CAM_IOSCHED_DYNAMIC 1017 struct sysctl_oid_list *n; 1018 #endif 1019 1020 SYSCTL_ADD_INT(ctx, SYSCTL_CHILDREN(node), 1021 OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE, 1022 &isc->sort_io_queue, 0, 1023 "Sort IO queue to try and optimise disk access patterns"); 1024 1025 #ifdef CAM_IOSCHED_DYNAMIC 1026 if (!do_dynamic_iosched) 1027 return; 1028 1029 isc->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1030 SYSCTL_CHILDREN(node), OID_AUTO, "iosched", 1031 CTLFLAG_RD, 0, "I/O scheduler statistics"); 1032 n = SYSCTL_CHILDREN(isc->sysctl_tree); 1033 ctx = &isc->sysctl_ctx; 1034 1035 cam_iosched_iop_stats_sysctl_init(isc, &isc->read_stats, "read"); 1036 cam_iosched_iop_stats_sysctl_init(isc, &isc->write_stats, "write"); 1037 cam_iosched_iop_stats_sysctl_init(isc, &isc->trim_stats, "trim"); 1038 cam_iosched_cl_sysctl_init(isc); 1039 1040 SYSCTL_ADD_INT(ctx, n, 1041 OID_AUTO, "read_bias", CTLFLAG_RW, 1042 &isc->read_bias, 100, 1043 "How biased towards read should we be independent of limits"); 1044 1045 SYSCTL_ADD_INT(ctx, n, 1046 OID_AUTO, "quanta", CTLFLAG_RW, 1047 &isc->quanta, 200, 1048 "How many quanta per second do we slice the I/O up into"); 1049 1050 SYSCTL_ADD_INT(ctx, n, 1051 OID_AUTO, "total_ticks", CTLFLAG_RD, 1052 &isc->total_ticks, 0, 1053 "Total number of ticks we've done"); 1054 #endif 1055 } 1056 1057 /* 1058 * Flush outstanding I/O. Consumers of this library don't know all the 1059 * queues we may keep, so this allows all I/O to be flushed in one 1060 * convenient call. 1061 */ 1062 void 1063 cam_iosched_flush(struct cam_iosched_softc *isc, struct devstat *stp, int err) 1064 { 1065 bioq_flush(&isc->bio_queue, stp, err); 1066 bioq_flush(&isc->trim_queue, stp, err); 1067 #ifdef CAM_IOSCHED_DYNAMIC 1068 if (do_dynamic_iosched) 1069 bioq_flush(&isc->write_queue, stp, err); 1070 #endif 1071 } 1072 1073 #ifdef CAM_IOSCHED_DYNAMIC 1074 static struct bio * 1075 cam_iosched_get_write(struct cam_iosched_softc *isc) 1076 { 1077 struct bio *bp; 1078 1079 /* 1080 * We control the write rate by controlling how many requests we send 1081 * down to the drive at any one time. Fewer requests limits the 1082 * effects of both starvation when the requests take a while and write 1083 * amplification when each request is causing more than one write to 1084 * the NAND media. Limiting the queue depth like this will also limit 1085 * the write throughput and give and reads that want to compete to 1086 * compete unfairly. 1087 */ 1088 bp = bioq_first(&isc->write_queue); 1089 if (bp == NULL) { 1090 if (iosched_debug > 3) 1091 printf("No writes present in write_queue\n"); 1092 return NULL; 1093 } 1094 1095 /* 1096 * If pending read, prefer that based on current read bias 1097 * setting. 1098 */ 1099 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) { 1100 if (iosched_debug) 1101 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); 1102 isc->current_read_bias--; 1103 return NULL; 1104 } 1105 1106 /* 1107 * See if our current limiter allows this I/O. 1108 */ 1109 if (cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) { 1110 if (iosched_debug) 1111 printf("Can't write because limiter says no.\n"); 1112 return NULL; 1113 } 1114 1115 /* 1116 * Let's do this: We've passed all the gates and we're a go 1117 * to schedule the I/O in the SIM. 1118 */ 1119 isc->current_read_bias = isc->read_bias; 1120 bioq_remove(&isc->write_queue, bp); 1121 if (bp->bio_cmd == BIO_WRITE) { 1122 isc->write_stats.queued--; 1123 isc->write_stats.total++; 1124 isc->write_stats.pending++; 1125 } 1126 if (iosched_debug > 9) 1127 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1128 return bp; 1129 } 1130 #endif 1131 1132 /* 1133 * Put back a trim that you weren't able to actually schedule this time. 1134 */ 1135 void 1136 cam_iosched_put_back_trim(struct cam_iosched_softc *isc, struct bio *bp) 1137 { 1138 bioq_insert_head(&isc->trim_queue, bp); 1139 #ifdef CAM_IOSCHED_DYNAMIC 1140 isc->trim_stats.queued++; 1141 isc->trim_stats.total--; /* since we put it back, don't double count */ 1142 isc->trim_stats.pending--; 1143 #endif 1144 } 1145 1146 /* 1147 * gets the next trim from the trim queue. 1148 * 1149 * Assumes we're called with the periph lock held. It removes this 1150 * trim from the queue and the device must explicitly reinstert it 1151 * should the need arise. 1152 */ 1153 struct bio * 1154 cam_iosched_next_trim(struct cam_iosched_softc *isc) 1155 { 1156 struct bio *bp; 1157 1158 bp = bioq_first(&isc->trim_queue); 1159 if (bp == NULL) 1160 return NULL; 1161 bioq_remove(&isc->trim_queue, bp); 1162 #ifdef CAM_IOSCHED_DYNAMIC 1163 isc->trim_stats.queued--; 1164 isc->trim_stats.total++; 1165 isc->trim_stats.pending++; 1166 #endif 1167 return bp; 1168 } 1169 1170 /* 1171 * gets the an available trim from the trim queue, if there's no trim 1172 * already pending. It removes this trim from the queue and the device 1173 * must explicitly reinstert it should the need arise. 1174 * 1175 * Assumes we're called with the periph lock held. 1176 */ 1177 struct bio * 1178 cam_iosched_get_trim(struct cam_iosched_softc *isc) 1179 { 1180 1181 if (!cam_iosched_has_more_trim(isc)) 1182 return NULL; 1183 1184 return cam_iosched_next_trim(isc); 1185 } 1186 1187 /* 1188 * Determine what the next bit of work to do is for the periph. The 1189 * default implementation looks to see if we have trims to do, but no 1190 * trims outstanding. If so, we do that. Otherwise we see if we have 1191 * other work. If we do, then we do that. Otherwise why were we called? 1192 */ 1193 struct bio * 1194 cam_iosched_next_bio(struct cam_iosched_softc *isc) 1195 { 1196 struct bio *bp; 1197 1198 /* 1199 * See if we have a trim that can be scheduled. We can only send one 1200 * at a time down, so this takes that into account. 1201 * 1202 * XXX newer TRIM commands are queueable. Revisit this when we 1203 * implement them. 1204 */ 1205 if ((bp = cam_iosched_get_trim(isc)) != NULL) 1206 return bp; 1207 1208 #ifdef CAM_IOSCHED_DYNAMIC 1209 /* 1210 * See if we have any pending writes, and room in the queue for them, 1211 * and if so, those are next. 1212 */ 1213 if (do_dynamic_iosched) { 1214 if ((bp = cam_iosched_get_write(isc)) != NULL) 1215 return bp; 1216 } 1217 #endif 1218 1219 /* 1220 * next, see if there's other, normal I/O waiting. If so return that. 1221 */ 1222 if ((bp = bioq_first(&isc->bio_queue)) == NULL) 1223 return NULL; 1224 1225 #ifdef CAM_IOSCHED_DYNAMIC 1226 /* 1227 * For the netflix scheduler, bio_queue is only for reads, so enforce 1228 * the limits here. Enforce only for reads. 1229 */ 1230 if (do_dynamic_iosched) { 1231 if (bp->bio_cmd == BIO_READ && 1232 cam_iosched_limiter_iop(&isc->read_stats, bp) != 0) 1233 return NULL; 1234 } 1235 #endif 1236 bioq_remove(&isc->bio_queue, bp); 1237 #ifdef CAM_IOSCHED_DYNAMIC 1238 if (do_dynamic_iosched) { 1239 if (bp->bio_cmd == BIO_READ) { 1240 isc->read_stats.queued--; 1241 isc->read_stats.total++; 1242 isc->read_stats.pending++; 1243 } else 1244 printf("Found bio_cmd = %#x\n", bp->bio_cmd); 1245 } 1246 if (iosched_debug > 9) 1247 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1248 #endif 1249 return bp; 1250 } 1251 1252 /* 1253 * Driver has been given some work to do by the block layer. Tell the 1254 * scheduler about it and have it queue the work up. The scheduler module 1255 * will then return the currently most useful bit of work later, possibly 1256 * deferring work for various reasons. 1257 */ 1258 void 1259 cam_iosched_queue_work(struct cam_iosched_softc *isc, struct bio *bp) 1260 { 1261 1262 /* 1263 * Put all trims on the trim queue sorted, since we know 1264 * that the collapsing code requires this. Otherwise put 1265 * the work on the bio queue. 1266 */ 1267 if (bp->bio_cmd == BIO_DELETE) { 1268 bioq_disksort(&isc->trim_queue, bp); 1269 #ifdef CAM_IOSCHED_DYNAMIC 1270 isc->trim_stats.in++; 1271 isc->trim_stats.queued++; 1272 #endif 1273 } 1274 #ifdef CAM_IOSCHED_DYNAMIC 1275 else if (do_dynamic_iosched && 1276 (bp->bio_cmd == BIO_WRITE || bp->bio_cmd == BIO_FLUSH)) { 1277 if (cam_iosched_sort_queue(isc)) 1278 bioq_disksort(&isc->write_queue, bp); 1279 else 1280 bioq_insert_tail(&isc->write_queue, bp); 1281 if (iosched_debug > 9) 1282 printf("Qw : %p %#x\n", bp, bp->bio_cmd); 1283 if (bp->bio_cmd == BIO_WRITE) { 1284 isc->write_stats.in++; 1285 isc->write_stats.queued++; 1286 } 1287 } 1288 #endif 1289 else { 1290 if (cam_iosched_sort_queue(isc)) 1291 bioq_disksort(&isc->bio_queue, bp); 1292 else 1293 bioq_insert_tail(&isc->bio_queue, bp); 1294 #ifdef CAM_IOSCHED_DYNAMIC 1295 if (iosched_debug > 9) 1296 printf("Qr : %p %#x\n", bp, bp->bio_cmd); 1297 if (bp->bio_cmd == BIO_READ) { 1298 isc->read_stats.in++; 1299 isc->read_stats.queued++; 1300 } else if (bp->bio_cmd == BIO_WRITE) { 1301 isc->write_stats.in++; 1302 isc->write_stats.queued++; 1303 } 1304 #endif 1305 } 1306 } 1307 1308 /* 1309 * If we have work, get it scheduled. Called with the periph lock held. 1310 */ 1311 void 1312 cam_iosched_schedule(struct cam_iosched_softc *isc, struct cam_periph *periph) 1313 { 1314 1315 if (cam_iosched_has_work(isc)) 1316 xpt_schedule(periph, CAM_PRIORITY_NORMAL); 1317 } 1318 1319 /* 1320 * Complete a trim request 1321 */ 1322 void 1323 cam_iosched_trim_done(struct cam_iosched_softc *isc) 1324 { 1325 1326 isc->flags &= ~CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1327 } 1328 1329 /* 1330 * Complete a bio. Called before we release the ccb with xpt_release_ccb so we 1331 * might use notes in the ccb for statistics. 1332 */ 1333 int 1334 cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp, 1335 union ccb *done_ccb) 1336 { 1337 int retval = 0; 1338 #ifdef CAM_IOSCHED_DYNAMIC 1339 if (!do_dynamic_iosched) 1340 return retval; 1341 1342 if (iosched_debug > 10) 1343 printf("done: %p %#x\n", bp, bp->bio_cmd); 1344 if (bp->bio_cmd == BIO_WRITE) { 1345 retval = cam_iosched_limiter_iodone(&isc->write_stats, bp); 1346 isc->write_stats.out++; 1347 isc->write_stats.pending--; 1348 } else if (bp->bio_cmd == BIO_READ) { 1349 retval = cam_iosched_limiter_iodone(&isc->read_stats, bp); 1350 isc->read_stats.out++; 1351 isc->read_stats.pending--; 1352 } else if (bp->bio_cmd == BIO_DELETE) { 1353 isc->trim_stats.out++; 1354 isc->trim_stats.pending--; 1355 } else if (bp->bio_cmd != BIO_FLUSH) { 1356 if (iosched_debug) 1357 printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd); 1358 } 1359 1360 if (!(bp->bio_flags & BIO_ERROR)) 1361 cam_iosched_io_metric_update(isc, done_ccb->ccb_h.qos.sim_data, 1362 bp->bio_cmd, bp->bio_bcount); 1363 #endif 1364 return retval; 1365 } 1366 1367 /* 1368 * Tell the io scheduler that you've pushed a trim down into the sim. 1369 * xxx better place for this? 1370 */ 1371 void 1372 cam_iosched_submit_trim(struct cam_iosched_softc *isc) 1373 { 1374 1375 isc->flags |= CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1376 } 1377 1378 /* 1379 * Change the sorting policy hint for I/O transactions for this device. 1380 */ 1381 void 1382 cam_iosched_set_sort_queue(struct cam_iosched_softc *isc, int val) 1383 { 1384 1385 isc->sort_io_queue = val; 1386 } 1387 1388 int 1389 cam_iosched_has_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1390 { 1391 return isc->flags & flags; 1392 } 1393 1394 void 1395 cam_iosched_set_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1396 { 1397 isc->flags |= flags; 1398 } 1399 1400 void 1401 cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1402 { 1403 isc->flags &= ~flags; 1404 } 1405 1406 #ifdef CAM_IOSCHED_DYNAMIC 1407 /* 1408 * After the method presented in Jack Crenshaw's 1998 article "Integer 1409 * Suqare Roots," reprinted at 1410 * http://www.embedded.com/electronics-blogs/programmer-s-toolbox/4219659/Integer-Square-Roots 1411 * and well worth the read. Briefly, we find the power of 4 that's the 1412 * largest smaller than val. We then check each smaller power of 4 to 1413 * see if val is still bigger. The right shifts at each step divide 1414 * the result by 2 which after successive application winds up 1415 * accumulating the right answer. It could also have been accumulated 1416 * using a separate root counter, but this code is smaller and faster 1417 * than that method. This method is also integer size invariant. 1418 * It returns floor(sqrt((float)val)), or the larget integer less than 1419 * or equal to the square root. 1420 */ 1421 static uint64_t 1422 isqrt64(uint64_t val) 1423 { 1424 uint64_t res = 0; 1425 uint64_t bit = 1ULL << (sizeof(uint64_t) * NBBY - 2); 1426 1427 /* 1428 * Find the largest power of 4 smaller than val. 1429 */ 1430 while (bit > val) 1431 bit >>= 2; 1432 1433 /* 1434 * Accumulate the answer, one bit at a time (we keep moving 1435 * them over since 2 is the square root of 4 and we test 1436 * powers of 4). We accumulate where we find the bit, but 1437 * the successive shifts land the bit in the right place 1438 * by the end. 1439 */ 1440 while (bit != 0) { 1441 if (val >= res + bit) { 1442 val -= res + bit; 1443 res = (res >> 1) + bit; 1444 } else 1445 res >>= 1; 1446 bit >>= 2; 1447 } 1448 1449 return res; 1450 } 1451 1452 /* 1453 * a and b are 32.32 fixed point stored in a 64-bit word. 1454 * Let al and bl be the .32 part of a and b. 1455 * Let ah and bh be the 32 part of a and b. 1456 * R is the radix and is 1 << 32 1457 * 1458 * a * b 1459 * (ah + al / R) * (bh + bl / R) 1460 * ah * bh + (al * bh + ah * bl) / R + al * bl / R^2 1461 * 1462 * After multiplicaiton, we have to renormalize by multiply by 1463 * R, so we wind up with 1464 * ah * bh * R + al * bh + ah * bl + al * bl / R 1465 * which turns out to be a very nice way to compute this value 1466 * so long as ah and bh are < 65536 there's no loss of high bits 1467 * and the low order bits are below the threshold of caring for 1468 * this application. 1469 */ 1470 static uint64_t 1471 mul(uint64_t a, uint64_t b) 1472 { 1473 uint64_t al, ah, bl, bh; 1474 al = a & 0xffffffff; 1475 ah = a >> 32; 1476 bl = b & 0xffffffff; 1477 bh = b >> 32; 1478 return ((ah * bh) << 32) + al * bh + ah * bl + ((al * bl) >> 32); 1479 } 1480 1481 static void 1482 cam_iosched_update(struct iop_stats *iop, sbintime_t sim_latency) 1483 { 1484 sbintime_t y, yy; 1485 uint64_t var; 1486 1487 /* 1488 * Classic expoentially decaying average with a tiny alpha 1489 * (2 ^ -alpha_bits). For more info see the NIST statistical 1490 * handbook. 1491 * 1492 * ema_t = y_t * alpha + ema_t-1 * (1 - alpha) 1493 * alpha = 1 / (1 << alpha_bits) 1494 * 1495 * Since alpha is a power of two, we can compute this w/o any mult or 1496 * division. 1497 */ 1498 y = sim_latency; 1499 iop->ema = (y + (iop->ema << alpha_bits) - iop->ema) >> alpha_bits; 1500 1501 yy = mul(y, y); 1502 iop->emss = (yy + (iop->emss << alpha_bits) - iop->emss) >> alpha_bits; 1503 1504 /* 1505 * s_1 = sum of data 1506 * s_2 = sum of data * data 1507 * ema ~ mean (or s_1 / N) 1508 * emss ~ s_2 / N 1509 * 1510 * sd = sqrt((N * s_2 - s_1 ^ 2) / (N * (N - 1))) 1511 * sd = sqrt((N * s_2 / N * (N - 1)) - (s_1 ^ 2 / (N * (N - 1)))) 1512 * 1513 * N ~ 2 / alpha - 1 1514 * alpha < 1 / 16 (typically much less) 1515 * N > 31 --> N large so N * (N - 1) is approx N * N 1516 * 1517 * substituting and rearranging: 1518 * sd ~ sqrt(s_2 / N - (s_1 / N) ^ 2) 1519 * ~ sqrt(emss - ema ^ 2); 1520 * which is the formula used here to get a decent estimate of sd which 1521 * we use to detect outliers. Note that when first starting up, it 1522 * takes a while for emss sum of squares estimator to converge on a 1523 * good value. during this time, it can be less than ema^2. We 1524 * compute a sd of 0 in that case, and ignore outliers. 1525 */ 1526 var = iop->emss - mul(iop->ema, iop->ema); 1527 iop->sd = (int64_t)var < 0 ? 0 : isqrt64(var); 1528 } 1529 1530 #ifdef CAM_IOSCHED_DYNAMIC 1531 static void 1532 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 1533 sbintime_t sim_latency, int cmd, size_t size) 1534 { 1535 /* xxx Do we need to scale based on the size of the I/O ? */ 1536 switch (cmd) { 1537 case BIO_READ: 1538 cam_iosched_update(&isc->read_stats, sim_latency); 1539 break; 1540 case BIO_WRITE: 1541 cam_iosched_update(&isc->write_stats, sim_latency); 1542 break; 1543 case BIO_DELETE: 1544 cam_iosched_update(&isc->trim_stats, sim_latency); 1545 break; 1546 default: 1547 break; 1548 } 1549 } 1550 #endif 1551 1552 #ifdef DDB 1553 static int biolen(struct bio_queue_head *bq) 1554 { 1555 int i = 0; 1556 struct bio *bp; 1557 1558 TAILQ_FOREACH(bp, &bq->queue, bio_queue) { 1559 i++; 1560 } 1561 return i; 1562 } 1563 1564 /* 1565 * Show the internal state of the I/O scheduler. 1566 */ 1567 DB_SHOW_COMMAND(iosched, cam_iosched_db_show) 1568 { 1569 struct cam_iosched_softc *isc; 1570 1571 if (!have_addr) { 1572 db_printf("Need addr\n"); 1573 return; 1574 } 1575 isc = (struct cam_iosched_softc *)addr; 1576 db_printf("pending_reads: %d\n", isc->read_stats.pending); 1577 db_printf("min_reads: %d\n", isc->read_stats.min); 1578 db_printf("max_reads: %d\n", isc->read_stats.max); 1579 db_printf("reads: %d\n", isc->read_stats.total); 1580 db_printf("in_reads: %d\n", isc->read_stats.in); 1581 db_printf("out_reads: %d\n", isc->read_stats.out); 1582 db_printf("queued_reads: %d\n", isc->read_stats.queued); 1583 db_printf("Current Q len %d\n", biolen(&isc->bio_queue)); 1584 db_printf("pending_writes: %d\n", isc->write_stats.pending); 1585 db_printf("min_writes: %d\n", isc->write_stats.min); 1586 db_printf("max_writes: %d\n", isc->write_stats.max); 1587 db_printf("writes: %d\n", isc->write_stats.total); 1588 db_printf("in_writes: %d\n", isc->write_stats.in); 1589 db_printf("out_writes: %d\n", isc->write_stats.out); 1590 db_printf("queued_writes: %d\n", isc->write_stats.queued); 1591 db_printf("Current Q len %d\n", biolen(&isc->write_queue)); 1592 db_printf("pending_trims: %d\n", isc->trim_stats.pending); 1593 db_printf("min_trims: %d\n", isc->trim_stats.min); 1594 db_printf("max_trims: %d\n", isc->trim_stats.max); 1595 db_printf("trims: %d\n", isc->trim_stats.total); 1596 db_printf("in_trims: %d\n", isc->trim_stats.in); 1597 db_printf("out_trims: %d\n", isc->trim_stats.out); 1598 db_printf("queued_trims: %d\n", isc->trim_stats.queued); 1599 db_printf("Current Q len %d\n", biolen(&isc->trim_queue)); 1600 db_printf("read_bias: %d\n", isc->read_bias); 1601 db_printf("current_read_bias: %d\n", isc->current_read_bias); 1602 db_printf("Trim active? %s\n", 1603 (isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) ? "yes" : "no"); 1604 } 1605 #endif 1606 #endif 1607