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 */ 97 static int alpha_bits = 9; 98 TUNABLE_INT("kern.cam.iosched_alpha_bits", &alpha_bits); 99 SYSCTL_INT(_kern_cam, OID_AUTO, iosched_alpha_bits, CTLFLAG_RW, 100 &alpha_bits, 1, 101 "Bits in EMA's alpha."); 102 103 struct iop_stats; 104 struct cam_iosched_softc; 105 106 int iosched_debug = 0; 107 108 typedef enum { 109 none = 0, /* No limits */ 110 queue_depth, /* Limit how many ops we queue to SIM */ 111 iops, /* Limit # of IOPS to the drive */ 112 bandwidth, /* Limit bandwidth to the drive */ 113 limiter_max 114 } io_limiter; 115 116 static const char *cam_iosched_limiter_names[] = 117 { "none", "queue_depth", "iops", "bandwidth" }; 118 119 /* 120 * Called to initialize the bits of the iop_stats structure relevant to the 121 * limiter. Called just after the limiter is set. 122 */ 123 typedef int l_init_t(struct iop_stats *); 124 125 /* 126 * Called every tick. 127 */ 128 typedef int l_tick_t(struct iop_stats *); 129 130 /* 131 * Called to see if the limiter thinks this IOP can be allowed to 132 * proceed. If so, the limiter assumes that the while IOP proceeded 133 * and makes any accounting of it that's needed. 134 */ 135 typedef int l_iop_t(struct iop_stats *, struct bio *); 136 137 /* 138 * Called when an I/O completes so the limiter can updates its 139 * accounting. Pending I/Os may complete in any order (even when 140 * sent to the hardware at the same time), so the limiter may not 141 * make any assumptions other than this I/O has completed. If it 142 * returns 1, then xpt_schedule() needs to be called again. 143 */ 144 typedef int l_iodone_t(struct iop_stats *, struct bio *); 145 146 static l_iop_t cam_iosched_qd_iop; 147 static l_iop_t cam_iosched_qd_caniop; 148 static l_iodone_t cam_iosched_qd_iodone; 149 150 static l_init_t cam_iosched_iops_init; 151 static l_tick_t cam_iosched_iops_tick; 152 static l_iop_t cam_iosched_iops_caniop; 153 static l_iop_t cam_iosched_iops_iop; 154 155 static l_init_t cam_iosched_bw_init; 156 static l_tick_t cam_iosched_bw_tick; 157 static l_iop_t cam_iosched_bw_caniop; 158 static l_iop_t cam_iosched_bw_iop; 159 160 struct limswitch { 161 l_init_t *l_init; 162 l_tick_t *l_tick; 163 l_iop_t *l_iop; 164 l_iop_t *l_caniop; 165 l_iodone_t *l_iodone; 166 } limsw[] = 167 { 168 { /* none */ 169 .l_init = NULL, 170 .l_tick = NULL, 171 .l_iop = NULL, 172 .l_iodone= NULL, 173 }, 174 { /* queue_depth */ 175 .l_init = NULL, 176 .l_tick = NULL, 177 .l_caniop = cam_iosched_qd_caniop, 178 .l_iop = cam_iosched_qd_iop, 179 .l_iodone= cam_iosched_qd_iodone, 180 }, 181 { /* iops */ 182 .l_init = cam_iosched_iops_init, 183 .l_tick = cam_iosched_iops_tick, 184 .l_caniop = cam_iosched_iops_caniop, 185 .l_iop = cam_iosched_iops_iop, 186 .l_iodone= NULL, 187 }, 188 { /* bandwidth */ 189 .l_init = cam_iosched_bw_init, 190 .l_tick = cam_iosched_bw_tick, 191 .l_caniop = cam_iosched_bw_caniop, 192 .l_iop = cam_iosched_bw_iop, 193 .l_iodone= NULL, 194 }, 195 }; 196 197 struct iop_stats { 198 /* 199 * sysctl state for this subnode. 200 */ 201 struct sysctl_ctx_list sysctl_ctx; 202 struct sysctl_oid *sysctl_tree; 203 204 /* 205 * Information about the current rate limiters, if any 206 */ 207 io_limiter limiter; /* How are I/Os being limited */ 208 int min; /* Low range of limit */ 209 int max; /* High range of limit */ 210 int current; /* Current rate limiter */ 211 int l_value1; /* per-limiter scratch value 1. */ 212 int l_value2; /* per-limiter scratch value 2. */ 213 214 /* 215 * Debug information about counts of I/Os that have gone through the 216 * scheduler. 217 */ 218 int pending; /* I/Os pending in the hardware */ 219 int queued; /* number currently in the queue */ 220 int total; /* Total for all time -- wraps */ 221 int in; /* number queued all time -- wraps */ 222 int out; /* number completed all time -- wraps */ 223 224 /* 225 * Statistics on different bits of the process. 226 */ 227 /* Exp Moving Average, see alpha_bits for more details */ 228 sbintime_t ema; 229 sbintime_t emss; /* Exp Moving sum of the squares */ 230 sbintime_t sd; /* Last computed sd */ 231 232 uint32_t state_flags; 233 #define IOP_RATE_LIMITED 1u 234 235 #define LAT_BUCKETS 12 /* < 1ms < 2ms ... 512ms < 1024ms > 1024ms */ 236 uint64_t latencies[LAT_BUCKETS]; 237 238 struct cam_iosched_softc *softc; 239 }; 240 241 242 typedef enum { 243 set_max = 0, /* current = max */ 244 read_latency, /* Steer read latency by throttling writes */ 245 cl_max /* Keep last */ 246 } control_type; 247 248 static const char *cam_iosched_control_type_names[] = 249 { "set_max", "read_latency" }; 250 251 struct control_loop { 252 /* 253 * sysctl state for this subnode. 254 */ 255 struct sysctl_ctx_list sysctl_ctx; 256 struct sysctl_oid *sysctl_tree; 257 258 sbintime_t next_steer; /* Time of next steer */ 259 sbintime_t steer_interval; /* How often do we steer? */ 260 sbintime_t lolat; 261 sbintime_t hilat; 262 int alpha; 263 control_type type; /* What type of control? */ 264 int last_count; /* Last I/O count */ 265 266 struct cam_iosched_softc *softc; 267 }; 268 269 #endif 270 271 struct cam_iosched_softc { 272 struct bio_queue_head bio_queue; 273 struct bio_queue_head trim_queue; 274 /* scheduler flags < 16, user flags >= 16 */ 275 uint32_t flags; 276 int sort_io_queue; 277 #ifdef CAM_IOSCHED_DYNAMIC 278 int read_bias; /* Read bias setting */ 279 int current_read_bias; /* Current read bias state */ 280 int total_ticks; 281 int load; /* EMA of 'load average' of disk / 2^16 */ 282 283 struct bio_queue_head write_queue; 284 struct iop_stats read_stats, write_stats, trim_stats; 285 struct sysctl_ctx_list sysctl_ctx; 286 struct sysctl_oid *sysctl_tree; 287 288 int quanta; /* Number of quanta per second */ 289 struct callout ticker; /* Callout for our quota system */ 290 struct cam_periph *periph; /* cam periph associated with this device */ 291 uint32_t this_frac; /* Fraction of a second (1024ths) for this tick */ 292 sbintime_t last_time; /* Last time we ticked */ 293 struct control_loop cl; 294 #endif 295 }; 296 297 #ifdef CAM_IOSCHED_DYNAMIC 298 /* 299 * helper functions to call the limsw functions. 300 */ 301 static int 302 cam_iosched_limiter_init(struct iop_stats *ios) 303 { 304 int lim = ios->limiter; 305 306 /* maybe this should be a kassert */ 307 if (lim < none || lim >= limiter_max) 308 return EINVAL; 309 310 if (limsw[lim].l_init) 311 return limsw[lim].l_init(ios); 312 313 return 0; 314 } 315 316 static int 317 cam_iosched_limiter_tick(struct iop_stats *ios) 318 { 319 int lim = ios->limiter; 320 321 /* maybe this should be a kassert */ 322 if (lim < none || lim >= limiter_max) 323 return EINVAL; 324 325 if (limsw[lim].l_tick) 326 return limsw[lim].l_tick(ios); 327 328 return 0; 329 } 330 331 static int 332 cam_iosched_limiter_iop(struct iop_stats *ios, struct bio *bp) 333 { 334 int lim = ios->limiter; 335 336 /* maybe this should be a kassert */ 337 if (lim < none || lim >= limiter_max) 338 return EINVAL; 339 340 if (limsw[lim].l_iop) 341 return limsw[lim].l_iop(ios, bp); 342 343 return 0; 344 } 345 346 static int 347 cam_iosched_limiter_caniop(struct iop_stats *ios, struct bio *bp) 348 { 349 int lim = ios->limiter; 350 351 /* maybe this should be a kassert */ 352 if (lim < none || lim >= limiter_max) 353 return EINVAL; 354 355 if (limsw[lim].l_caniop) 356 return limsw[lim].l_caniop(ios, bp); 357 358 return 0; 359 } 360 361 static int 362 cam_iosched_limiter_iodone(struct iop_stats *ios, struct bio *bp) 363 { 364 int lim = ios->limiter; 365 366 /* maybe this should be a kassert */ 367 if (lim < none || lim >= limiter_max) 368 return 0; 369 370 if (limsw[lim].l_iodone) 371 return limsw[lim].l_iodone(ios, bp); 372 373 return 0; 374 } 375 376 /* 377 * Functions to implement the different kinds of limiters 378 */ 379 380 static int 381 cam_iosched_qd_iop(struct iop_stats *ios, struct bio *bp) 382 { 383 384 if (ios->current <= 0 || ios->pending < ios->current) 385 return 0; 386 387 return EAGAIN; 388 } 389 390 static int 391 cam_iosched_qd_caniop(struct iop_stats *ios, struct bio *bp) 392 { 393 394 if (ios->current <= 0 || ios->pending < ios->current) 395 return 0; 396 397 return EAGAIN; 398 } 399 400 static int 401 cam_iosched_qd_iodone(struct iop_stats *ios, struct bio *bp) 402 { 403 404 if (ios->current <= 0 || ios->pending != ios->current) 405 return 0; 406 407 return 1; 408 } 409 410 static int 411 cam_iosched_iops_init(struct iop_stats *ios) 412 { 413 414 ios->l_value1 = ios->current / ios->softc->quanta; 415 if (ios->l_value1 <= 0) 416 ios->l_value1 = 1; 417 418 return 0; 419 } 420 421 static int 422 cam_iosched_iops_tick(struct iop_stats *ios) 423 { 424 425 ios->l_value1 = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16); 426 if (ios->l_value1 <= 0) 427 ios->l_value1 = 1; 428 429 return 0; 430 } 431 432 static int 433 cam_iosched_iops_caniop(struct iop_stats *ios, struct bio *bp) 434 { 435 436 /* 437 * So if we have any more IOPs left, allow it, 438 * otherwise wait. 439 */ 440 if (ios->l_value1 <= 0) 441 return EAGAIN; 442 return 0; 443 } 444 445 static int 446 cam_iosched_iops_iop(struct iop_stats *ios, struct bio *bp) 447 { 448 int rv; 449 450 rv = cam_iosched_limiter_caniop(ios, bp); 451 if (rv == 0) 452 ios->l_value1--; 453 454 return rv; 455 } 456 457 static int 458 cam_iosched_bw_init(struct iop_stats *ios) 459 { 460 461 /* ios->current is in kB/s, so scale to bytes */ 462 ios->l_value1 = ios->current * 1000 / ios->softc->quanta; 463 464 return 0; 465 } 466 467 static int 468 cam_iosched_bw_tick(struct iop_stats *ios) 469 { 470 int bw; 471 472 /* 473 * If we're in the hole for available quota from 474 * the last time, then add the quantum for this. 475 * If we have any left over from last quantum, 476 * then too bad, that's lost. Also, ios->current 477 * is in kB/s, so scale. 478 * 479 * We also allow up to 4 quanta of credits to 480 * accumulate to deal with burstiness. 4 is extremely 481 * arbitrary. 482 */ 483 bw = (int)((ios->current * 1000ull * (uint64_t)ios->softc->this_frac) >> 16); 484 if (ios->l_value1 < bw * 4) 485 ios->l_value1 += bw; 486 487 return 0; 488 } 489 490 static int 491 cam_iosched_bw_caniop(struct iop_stats *ios, struct bio *bp) 492 { 493 /* 494 * So if we have any more bw quota left, allow it, 495 * otherwise wait. Not, we'll go negative and that's 496 * OK. We'll just get a lettle less next quota. 497 * 498 * Note on going negative: that allows us to process 499 * requests in order better, since we won't allow 500 * shorter reads to get around the long one that we 501 * don't have the quota to do just yet. It also prevents 502 * starvation by being a little more permissive about 503 * what we let through this quantum (to prevent the 504 * starvation), at the cost of getting a little less 505 * next quantum. 506 */ 507 if (ios->l_value1 <= 0) 508 return EAGAIN; 509 510 511 return 0; 512 } 513 514 static int 515 cam_iosched_bw_iop(struct iop_stats *ios, struct bio *bp) 516 { 517 int rv; 518 519 rv = cam_iosched_limiter_caniop(ios, bp); 520 if (rv == 0) 521 ios->l_value1 -= bp->bio_length; 522 523 return rv; 524 } 525 526 static void cam_iosched_cl_maybe_steer(struct control_loop *clp); 527 528 static void 529 cam_iosched_ticker(void *arg) 530 { 531 struct cam_iosched_softc *isc = arg; 532 sbintime_t now, delta; 533 int pending; 534 535 callout_reset(&isc->ticker, hz / isc->quanta - 1, cam_iosched_ticker, isc); 536 537 now = sbinuptime(); 538 delta = now - isc->last_time; 539 isc->this_frac = (uint32_t)delta >> 16; /* Note: discards seconds -- should be 0 harmless if not */ 540 isc->last_time = now; 541 542 cam_iosched_cl_maybe_steer(&isc->cl); 543 544 cam_iosched_limiter_tick(&isc->read_stats); 545 cam_iosched_limiter_tick(&isc->write_stats); 546 cam_iosched_limiter_tick(&isc->trim_stats); 547 548 cam_iosched_schedule(isc, isc->periph); 549 550 /* 551 * isc->load is an EMA of the pending I/Os at each tick. The number of 552 * pending I/Os is the sum of the I/Os queued to the hardware, and those 553 * in the software queue that could be queued to the hardware if there 554 * were slots. 555 * 556 * ios_stats.pending is a count of requests in the SIM right now for 557 * each of these types of I/O. So the total pending count is the sum of 558 * these I/Os and the sum of the queued I/Os still in the software queue 559 * for those operations that aren't being rate limited at the moment. 560 * 561 * The reason for the rate limiting bit is because those I/Os 562 * aren't part of the software queued load (since we could 563 * give them to hardware, but choose not to). 564 * 565 * Note: due to a bug in counting pending TRIM in the device, we 566 * don't include them in this count. We count each BIO_DELETE in 567 * the pending count, but the periph drivers collapse them down 568 * into one TRIM command. That one trim command gets the completion 569 * so the counts get off. 570 */ 571 pending = isc->read_stats.pending + isc->write_stats.pending /* + isc->trim_stats.pending */; 572 pending += !!(isc->read_stats.state_flags & IOP_RATE_LIMITED) * isc->read_stats.queued + 573 !!(isc->write_stats.state_flags & IOP_RATE_LIMITED) * isc->write_stats.queued /* + 574 !!(isc->trim_stats.state_flags & IOP_RATE_LIMITED) * isc->trim_stats.queued */ ; 575 pending <<= 16; 576 pending /= isc->periph->path->device->ccbq.total_openings; 577 578 isc->load = (pending + (isc->load << 13) - isc->load) >> 13; /* see above: 13 -> 16139 / 200/s = ~81s ~1 minute */ 579 580 isc->total_ticks++; 581 } 582 583 584 static void 585 cam_iosched_cl_init(struct control_loop *clp, struct cam_iosched_softc *isc) 586 { 587 588 clp->next_steer = sbinuptime(); 589 clp->softc = isc; 590 clp->steer_interval = SBT_1S * 5; /* Let's start out steering every 5s */ 591 clp->lolat = 5 * SBT_1MS; 592 clp->hilat = 15 * SBT_1MS; 593 clp->alpha = 20; /* Alpha == gain. 20 = .2 */ 594 clp->type = set_max; 595 } 596 597 static void 598 cam_iosched_cl_maybe_steer(struct control_loop *clp) 599 { 600 struct cam_iosched_softc *isc; 601 sbintime_t now, lat; 602 int old; 603 604 isc = clp->softc; 605 now = isc->last_time; 606 if (now < clp->next_steer) 607 return; 608 609 clp->next_steer = now + clp->steer_interval; 610 switch (clp->type) { 611 case set_max: 612 if (isc->write_stats.current != isc->write_stats.max) 613 printf("Steering write from %d kBps to %d kBps\n", 614 isc->write_stats.current, isc->write_stats.max); 615 isc->read_stats.current = isc->read_stats.max; 616 isc->write_stats.current = isc->write_stats.max; 617 isc->trim_stats.current = isc->trim_stats.max; 618 break; 619 case read_latency: 620 old = isc->write_stats.current; 621 lat = isc->read_stats.ema; 622 /* 623 * Simple PLL-like engine. Since we're steering to a range for 624 * the SP (set point) that makes things a little more 625 * complicated. In addition, we're not directly controlling our 626 * PV (process variable), the read latency, but instead are 627 * manipulating the write bandwidth limit for our MV 628 * (manipulation variable), analysis of this code gets a bit 629 * messy. Also, the MV is a very noisy control surface for read 630 * latency since it is affected by many hidden processes inside 631 * the device which change how responsive read latency will be 632 * in reaction to changes in write bandwidth. Unlike the classic 633 * boiler control PLL. this may result in over-steering while 634 * the SSD takes its time to react to the new, lower load. This 635 * is why we use a relatively low alpha of between .1 and .25 to 636 * compensate for this effect. At .1, it takes ~22 steering 637 * intervals to back off by a factor of 10. At .2 it only takes 638 * ~10. At .25 it only takes ~8. However some preliminary data 639 * from the SSD drives suggests a reasponse time in 10's of 640 * seconds before latency drops regardless of the new write 641 * rate. Careful observation will be reqiured to tune this 642 * effectively. 643 * 644 * Also, when there's no read traffic, we jack up the write 645 * limit too regardless of the last read latency. 10 is 646 * somewhat arbitrary. 647 */ 648 if (lat < clp->lolat || isc->read_stats.total - clp->last_count < 10) 649 isc->write_stats.current = isc->write_stats.current * 650 (100 + clp->alpha) / 100; /* Scale up */ 651 else if (lat > clp->hilat) 652 isc->write_stats.current = isc->write_stats.current * 653 (100 - clp->alpha) / 100; /* Scale down */ 654 clp->last_count = isc->read_stats.total; 655 656 /* 657 * Even if we don't steer, per se, enforce the min/max limits as 658 * those may have changed. 659 */ 660 if (isc->write_stats.current < isc->write_stats.min) 661 isc->write_stats.current = isc->write_stats.min; 662 if (isc->write_stats.current > isc->write_stats.max) 663 isc->write_stats.current = isc->write_stats.max; 664 if (old != isc->write_stats.current && iosched_debug) 665 printf("Steering write from %d kBps to %d kBps due to latency of %jdus\n", 666 old, isc->write_stats.current, 667 (uintmax_t)((uint64_t)1000000 * (uint32_t)lat) >> 32); 668 break; 669 case cl_max: 670 break; 671 } 672 } 673 #endif 674 675 /* Trim or similar currently pending completion */ 676 #define CAM_IOSCHED_FLAG_TRIM_ACTIVE (1ul << 0) 677 /* Callout active, and needs to be torn down */ 678 #define CAM_IOSCHED_FLAG_CALLOUT_ACTIVE (1ul << 1) 679 680 /* Periph drivers set these flags to indicate work */ 681 #define CAM_IOSCHED_FLAG_WORK_FLAGS ((0xffffu) << 16) 682 683 #ifdef CAM_IOSCHED_DYNAMIC 684 static void 685 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 686 sbintime_t sim_latency, int cmd, size_t size); 687 #endif 688 689 static inline int 690 cam_iosched_has_flagged_work(struct cam_iosched_softc *isc) 691 { 692 return !!(isc->flags & CAM_IOSCHED_FLAG_WORK_FLAGS); 693 } 694 695 static inline int 696 cam_iosched_has_io(struct cam_iosched_softc *isc) 697 { 698 #ifdef CAM_IOSCHED_DYNAMIC 699 if (do_dynamic_iosched) { 700 struct bio *rbp = bioq_first(&isc->bio_queue); 701 struct bio *wbp = bioq_first(&isc->write_queue); 702 int can_write = wbp != NULL && 703 cam_iosched_limiter_caniop(&isc->write_stats, wbp) == 0; 704 int can_read = rbp != NULL && 705 cam_iosched_limiter_caniop(&isc->read_stats, rbp) == 0; 706 if (iosched_debug > 2) { 707 printf("can write %d: pending_writes %d max_writes %d\n", can_write, isc->write_stats.pending, isc->write_stats.max); 708 printf("can read %d: read_stats.pending %d max_reads %d\n", can_read, isc->read_stats.pending, isc->read_stats.max); 709 printf("Queued reads %d writes %d\n", isc->read_stats.queued, isc->write_stats.queued); 710 } 711 return can_read || can_write; 712 } 713 #endif 714 return bioq_first(&isc->bio_queue) != NULL; 715 } 716 717 static inline int 718 cam_iosched_has_more_trim(struct cam_iosched_softc *isc) 719 { 720 return !(isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) && 721 bioq_first(&isc->trim_queue); 722 } 723 724 #define cam_iosched_sort_queue(isc) ((isc)->sort_io_queue >= 0 ? \ 725 (isc)->sort_io_queue : cam_sort_io_queues) 726 727 728 static inline int 729 cam_iosched_has_work(struct cam_iosched_softc *isc) 730 { 731 #ifdef CAM_IOSCHED_DYNAMIC 732 if (iosched_debug > 2) 733 printf("has work: %d %d %d\n", cam_iosched_has_io(isc), 734 cam_iosched_has_more_trim(isc), 735 cam_iosched_has_flagged_work(isc)); 736 #endif 737 738 return cam_iosched_has_io(isc) || 739 cam_iosched_has_more_trim(isc) || 740 cam_iosched_has_flagged_work(isc); 741 } 742 743 #ifdef CAM_IOSCHED_DYNAMIC 744 static void 745 cam_iosched_iop_stats_init(struct cam_iosched_softc *isc, struct iop_stats *ios) 746 { 747 748 ios->limiter = none; 749 cam_iosched_limiter_init(ios); 750 ios->in = 0; 751 ios->max = 300000; 752 ios->min = 1; 753 ios->out = 0; 754 ios->pending = 0; 755 ios->queued = 0; 756 ios->total = 0; 757 ios->ema = 0; 758 ios->emss = 0; 759 ios->sd = 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, "emss", CTLFLAG_RD, 901 &ios->emss, 902 "Fast Exponentially Weighted Moving Sum of Squares (maybe wrong)"); 903 SYSCTL_ADD_UQUAD(ctx, n, 904 OID_AUTO, "sd", CTLFLAG_RD, 905 &ios->sd, 906 "Estimated SD for fast ema (may be wrong)"); 907 908 SYSCTL_ADD_INT(ctx, n, 909 OID_AUTO, "pending", CTLFLAG_RD, 910 &ios->pending, 0, 911 "Instantaneous # of pending transactions"); 912 SYSCTL_ADD_INT(ctx, n, 913 OID_AUTO, "count", CTLFLAG_RD, 914 &ios->total, 0, 915 "# of transactions submitted to hardware"); 916 SYSCTL_ADD_INT(ctx, n, 917 OID_AUTO, "queued", CTLFLAG_RD, 918 &ios->queued, 0, 919 "# of transactions in the queue"); 920 SYSCTL_ADD_INT(ctx, n, 921 OID_AUTO, "in", CTLFLAG_RD, 922 &ios->in, 0, 923 "# of transactions queued to driver"); 924 SYSCTL_ADD_INT(ctx, n, 925 OID_AUTO, "out", CTLFLAG_RD, 926 &ios->out, 0, 927 "# of transactions completed"); 928 929 SYSCTL_ADD_PROC(ctx, n, 930 OID_AUTO, "limiter", CTLTYPE_STRING | CTLFLAG_RW, 931 ios, 0, cam_iosched_limiter_sysctl, "A", 932 "Current limiting type."); 933 SYSCTL_ADD_INT(ctx, n, 934 OID_AUTO, "min", CTLFLAG_RW, 935 &ios->min, 0, 936 "min resource"); 937 SYSCTL_ADD_INT(ctx, n, 938 OID_AUTO, "max", CTLFLAG_RW, 939 &ios->max, 0, 940 "max resource"); 941 SYSCTL_ADD_INT(ctx, n, 942 OID_AUTO, "current", CTLFLAG_RW, 943 &ios->current, 0, 944 "current resource"); 945 946 SYSCTL_ADD_PROC(ctx, n, 947 OID_AUTO, "latencies", CTLTYPE_STRING | CTLFLAG_RD, 948 &ios->latencies, 0, 949 cam_iosched_sysctl_latencies, "A", 950 "Array of power of 2 latency from 1ms to 1.024s"); 951 } 952 953 static void 954 cam_iosched_iop_stats_fini(struct iop_stats *ios) 955 { 956 if (ios->sysctl_tree) 957 if (sysctl_ctx_free(&ios->sysctl_ctx) != 0) 958 printf("can't remove iosched sysctl stats context\n"); 959 } 960 961 static void 962 cam_iosched_cl_sysctl_init(struct cam_iosched_softc *isc) 963 { 964 struct sysctl_oid_list *n; 965 struct sysctl_ctx_list *ctx; 966 struct control_loop *clp; 967 968 clp = &isc->cl; 969 clp->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 970 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, "control", 971 CTLFLAG_RD, 0, "Control loop info"); 972 n = SYSCTL_CHILDREN(clp->sysctl_tree); 973 ctx = &clp->sysctl_ctx; 974 975 SYSCTL_ADD_PROC(ctx, n, 976 OID_AUTO, "type", CTLTYPE_STRING | CTLFLAG_RW, 977 clp, 0, cam_iosched_control_type_sysctl, "A", 978 "Control loop algorithm"); 979 SYSCTL_ADD_PROC(ctx, n, 980 OID_AUTO, "steer_interval", CTLTYPE_STRING | CTLFLAG_RW, 981 &clp->steer_interval, 0, cam_iosched_sbintime_sysctl, "A", 982 "How often to steer (in us)"); 983 SYSCTL_ADD_PROC(ctx, n, 984 OID_AUTO, "lolat", CTLTYPE_STRING | CTLFLAG_RW, 985 &clp->lolat, 0, cam_iosched_sbintime_sysctl, "A", 986 "Low water mark for Latency (in us)"); 987 SYSCTL_ADD_PROC(ctx, n, 988 OID_AUTO, "hilat", CTLTYPE_STRING | CTLFLAG_RW, 989 &clp->hilat, 0, cam_iosched_sbintime_sysctl, "A", 990 "Hi water mark for Latency (in us)"); 991 SYSCTL_ADD_INT(ctx, n, 992 OID_AUTO, "alpha", CTLFLAG_RW, 993 &clp->alpha, 0, 994 "Alpha for PLL (x100) aka gain"); 995 } 996 997 static void 998 cam_iosched_cl_sysctl_fini(struct control_loop *clp) 999 { 1000 if (clp->sysctl_tree) 1001 if (sysctl_ctx_free(&clp->sysctl_ctx) != 0) 1002 printf("can't remove iosched sysctl control loop context\n"); 1003 } 1004 #endif 1005 1006 /* 1007 * Allocate the iosched structure. This also insulates callers from knowing 1008 * sizeof struct cam_iosched_softc. 1009 */ 1010 int 1011 cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph) 1012 { 1013 1014 *iscp = malloc(sizeof(**iscp), M_CAMSCHED, M_NOWAIT | M_ZERO); 1015 if (*iscp == NULL) 1016 return ENOMEM; 1017 #ifdef CAM_IOSCHED_DYNAMIC 1018 if (iosched_debug) 1019 printf("CAM IOSCHEDULER Allocating entry at %p\n", *iscp); 1020 #endif 1021 (*iscp)->sort_io_queue = -1; 1022 bioq_init(&(*iscp)->bio_queue); 1023 bioq_init(&(*iscp)->trim_queue); 1024 #ifdef CAM_IOSCHED_DYNAMIC 1025 if (do_dynamic_iosched) { 1026 bioq_init(&(*iscp)->write_queue); 1027 (*iscp)->read_bias = 100; 1028 (*iscp)->current_read_bias = 100; 1029 (*iscp)->quanta = 200; 1030 cam_iosched_iop_stats_init(*iscp, &(*iscp)->read_stats); 1031 cam_iosched_iop_stats_init(*iscp, &(*iscp)->write_stats); 1032 cam_iosched_iop_stats_init(*iscp, &(*iscp)->trim_stats); 1033 (*iscp)->trim_stats.max = 1; /* Trims are special: one at a time for now */ 1034 (*iscp)->last_time = sbinuptime(); 1035 callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0); 1036 (*iscp)->periph = periph; 1037 cam_iosched_cl_init(&(*iscp)->cl, *iscp); 1038 callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta - 1, cam_iosched_ticker, *iscp); 1039 (*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1040 } 1041 #endif 1042 1043 return 0; 1044 } 1045 1046 /* 1047 * Reclaim all used resources. This assumes that other folks have 1048 * drained the requests in the hardware. Maybe an unwise assumption. 1049 */ 1050 void 1051 cam_iosched_fini(struct cam_iosched_softc *isc) 1052 { 1053 if (isc) { 1054 cam_iosched_flush(isc, NULL, ENXIO); 1055 #ifdef CAM_IOSCHED_DYNAMIC 1056 cam_iosched_iop_stats_fini(&isc->read_stats); 1057 cam_iosched_iop_stats_fini(&isc->write_stats); 1058 cam_iosched_iop_stats_fini(&isc->trim_stats); 1059 cam_iosched_cl_sysctl_fini(&isc->cl); 1060 if (isc->sysctl_tree) 1061 if (sysctl_ctx_free(&isc->sysctl_ctx) != 0) 1062 printf("can't remove iosched sysctl stats context\n"); 1063 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) { 1064 callout_drain(&isc->ticker); 1065 isc->flags &= ~ CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1066 } 1067 #endif 1068 free(isc, M_CAMSCHED); 1069 } 1070 } 1071 1072 /* 1073 * After we're sure we're attaching a device, go ahead and add 1074 * hooks for any sysctl we may wish to honor. 1075 */ 1076 void cam_iosched_sysctl_init(struct cam_iosched_softc *isc, 1077 struct sysctl_ctx_list *ctx, struct sysctl_oid *node) 1078 { 1079 #ifdef CAM_IOSCHED_DYNAMIC 1080 struct sysctl_oid_list *n; 1081 #endif 1082 1083 SYSCTL_ADD_INT(ctx, SYSCTL_CHILDREN(node), 1084 OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE, 1085 &isc->sort_io_queue, 0, 1086 "Sort IO queue to try and optimise disk access patterns"); 1087 1088 #ifdef CAM_IOSCHED_DYNAMIC 1089 if (!do_dynamic_iosched) 1090 return; 1091 1092 isc->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1093 SYSCTL_CHILDREN(node), OID_AUTO, "iosched", 1094 CTLFLAG_RD, 0, "I/O scheduler statistics"); 1095 n = SYSCTL_CHILDREN(isc->sysctl_tree); 1096 ctx = &isc->sysctl_ctx; 1097 1098 cam_iosched_iop_stats_sysctl_init(isc, &isc->read_stats, "read"); 1099 cam_iosched_iop_stats_sysctl_init(isc, &isc->write_stats, "write"); 1100 cam_iosched_iop_stats_sysctl_init(isc, &isc->trim_stats, "trim"); 1101 cam_iosched_cl_sysctl_init(isc); 1102 1103 SYSCTL_ADD_INT(ctx, n, 1104 OID_AUTO, "read_bias", CTLFLAG_RW, 1105 &isc->read_bias, 100, 1106 "How biased towards read should we be independent of limits"); 1107 1108 SYSCTL_ADD_INT(ctx, n, 1109 OID_AUTO, "quanta", CTLFLAG_RW, 1110 &isc->quanta, 200, 1111 "How many quanta per second do we slice the I/O up into"); 1112 1113 SYSCTL_ADD_INT(ctx, n, 1114 OID_AUTO, "total_ticks", CTLFLAG_RD, 1115 &isc->total_ticks, 0, 1116 "Total number of ticks we've done"); 1117 1118 SYSCTL_ADD_INT(ctx, n, 1119 OID_AUTO, "load", CTLFLAG_RD, 1120 &isc->load, 0, 1121 "scaled load average / 100"); 1122 #endif 1123 } 1124 1125 /* 1126 * Flush outstanding I/O. Consumers of this library don't know all the 1127 * queues we may keep, so this allows all I/O to be flushed in one 1128 * convenient call. 1129 */ 1130 void 1131 cam_iosched_flush(struct cam_iosched_softc *isc, struct devstat *stp, int err) 1132 { 1133 bioq_flush(&isc->bio_queue, stp, err); 1134 bioq_flush(&isc->trim_queue, stp, err); 1135 #ifdef CAM_IOSCHED_DYNAMIC 1136 if (do_dynamic_iosched) 1137 bioq_flush(&isc->write_queue, stp, err); 1138 #endif 1139 } 1140 1141 #ifdef CAM_IOSCHED_DYNAMIC 1142 static struct bio * 1143 cam_iosched_get_write(struct cam_iosched_softc *isc) 1144 { 1145 struct bio *bp; 1146 1147 /* 1148 * We control the write rate by controlling how many requests we send 1149 * down to the drive at any one time. Fewer requests limits the 1150 * effects of both starvation when the requests take a while and write 1151 * amplification when each request is causing more than one write to 1152 * the NAND media. Limiting the queue depth like this will also limit 1153 * the write throughput and give and reads that want to compete to 1154 * compete unfairly. 1155 */ 1156 bp = bioq_first(&isc->write_queue); 1157 if (bp == NULL) { 1158 if (iosched_debug > 3) 1159 printf("No writes present in write_queue\n"); 1160 return NULL; 1161 } 1162 1163 /* 1164 * If pending read, prefer that based on current read bias 1165 * setting. 1166 */ 1167 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) { 1168 if (iosched_debug) 1169 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); 1170 isc->current_read_bias--; 1171 /* We're not limiting writes, per se, just doing reads first */ 1172 return NULL; 1173 } 1174 1175 /* 1176 * See if our current limiter allows this I/O. 1177 */ 1178 if (cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) { 1179 if (iosched_debug) 1180 printf("Can't write because limiter says no.\n"); 1181 isc->write_stats.state_flags |= IOP_RATE_LIMITED; 1182 return NULL; 1183 } 1184 1185 /* 1186 * Let's do this: We've passed all the gates and we're a go 1187 * to schedule the I/O in the SIM. 1188 */ 1189 isc->current_read_bias = isc->read_bias; 1190 bioq_remove(&isc->write_queue, bp); 1191 if (bp->bio_cmd == BIO_WRITE) { 1192 isc->write_stats.queued--; 1193 isc->write_stats.total++; 1194 isc->write_stats.pending++; 1195 } 1196 if (iosched_debug > 9) 1197 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1198 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED; 1199 return bp; 1200 } 1201 #endif 1202 1203 /* 1204 * Put back a trim that you weren't able to actually schedule this time. 1205 */ 1206 void 1207 cam_iosched_put_back_trim(struct cam_iosched_softc *isc, struct bio *bp) 1208 { 1209 bioq_insert_head(&isc->trim_queue, bp); 1210 #ifdef CAM_IOSCHED_DYNAMIC 1211 isc->trim_stats.queued++; 1212 isc->trim_stats.total--; /* since we put it back, don't double count */ 1213 isc->trim_stats.pending--; 1214 #endif 1215 } 1216 1217 /* 1218 * gets the next trim from the trim queue. 1219 * 1220 * Assumes we're called with the periph lock held. It removes this 1221 * trim from the queue and the device must explicitly reinstert it 1222 * should the need arise. 1223 */ 1224 struct bio * 1225 cam_iosched_next_trim(struct cam_iosched_softc *isc) 1226 { 1227 struct bio *bp; 1228 1229 bp = bioq_first(&isc->trim_queue); 1230 if (bp == NULL) 1231 return NULL; 1232 bioq_remove(&isc->trim_queue, bp); 1233 #ifdef CAM_IOSCHED_DYNAMIC 1234 isc->trim_stats.queued--; 1235 isc->trim_stats.total++; 1236 isc->trim_stats.pending++; 1237 #endif 1238 return bp; 1239 } 1240 1241 /* 1242 * gets the an available trim from the trim queue, if there's no trim 1243 * already pending. It removes this trim from the queue and the device 1244 * must explicitly reinstert it should the need arise. 1245 * 1246 * Assumes we're called with the periph lock held. 1247 */ 1248 struct bio * 1249 cam_iosched_get_trim(struct cam_iosched_softc *isc) 1250 { 1251 1252 if (!cam_iosched_has_more_trim(isc)) 1253 return NULL; 1254 1255 return cam_iosched_next_trim(isc); 1256 } 1257 1258 /* 1259 * Determine what the next bit of work to do is for the periph. The 1260 * default implementation looks to see if we have trims to do, but no 1261 * trims outstanding. If so, we do that. Otherwise we see if we have 1262 * other work. If we do, then we do that. Otherwise why were we called? 1263 */ 1264 struct bio * 1265 cam_iosched_next_bio(struct cam_iosched_softc *isc) 1266 { 1267 struct bio *bp; 1268 1269 /* 1270 * See if we have a trim that can be scheduled. We can only send one 1271 * at a time down, so this takes that into account. 1272 * 1273 * XXX newer TRIM commands are queueable. Revisit this when we 1274 * implement them. 1275 */ 1276 if ((bp = cam_iosched_get_trim(isc)) != NULL) 1277 return bp; 1278 1279 #ifdef CAM_IOSCHED_DYNAMIC 1280 /* 1281 * See if we have any pending writes, and room in the queue for them, 1282 * and if so, those are next. 1283 */ 1284 if (do_dynamic_iosched) { 1285 if ((bp = cam_iosched_get_write(isc)) != NULL) 1286 return bp; 1287 } 1288 #endif 1289 1290 /* 1291 * next, see if there's other, normal I/O waiting. If so return that. 1292 */ 1293 if ((bp = bioq_first(&isc->bio_queue)) == NULL) 1294 return NULL; 1295 1296 #ifdef CAM_IOSCHED_DYNAMIC 1297 /* 1298 * For the dynamic scheduler, bio_queue is only for reads, so enforce 1299 * the limits here. Enforce only for reads. 1300 */ 1301 if (do_dynamic_iosched) { 1302 if (bp->bio_cmd == BIO_READ && 1303 cam_iosched_limiter_iop(&isc->read_stats, bp) != 0) { 1304 isc->read_stats.state_flags |= IOP_RATE_LIMITED; 1305 return NULL; 1306 } 1307 } 1308 isc->read_stats.state_flags &= ~IOP_RATE_LIMITED; 1309 #endif 1310 bioq_remove(&isc->bio_queue, bp); 1311 #ifdef CAM_IOSCHED_DYNAMIC 1312 if (do_dynamic_iosched) { 1313 if (bp->bio_cmd == BIO_READ) { 1314 isc->read_stats.queued--; 1315 isc->read_stats.total++; 1316 isc->read_stats.pending++; 1317 } else 1318 printf("Found bio_cmd = %#x\n", bp->bio_cmd); 1319 } 1320 if (iosched_debug > 9) 1321 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1322 #endif 1323 return bp; 1324 } 1325 1326 /* 1327 * Driver has been given some work to do by the block layer. Tell the 1328 * scheduler about it and have it queue the work up. The scheduler module 1329 * will then return the currently most useful bit of work later, possibly 1330 * deferring work for various reasons. 1331 */ 1332 void 1333 cam_iosched_queue_work(struct cam_iosched_softc *isc, struct bio *bp) 1334 { 1335 1336 /* 1337 * Put all trims on the trim queue sorted, since we know 1338 * that the collapsing code requires this. Otherwise put 1339 * the work on the bio queue. 1340 */ 1341 if (bp->bio_cmd == BIO_DELETE) { 1342 bioq_disksort(&isc->trim_queue, bp); 1343 #ifdef CAM_IOSCHED_DYNAMIC 1344 isc->trim_stats.in++; 1345 isc->trim_stats.queued++; 1346 #endif 1347 } 1348 #ifdef CAM_IOSCHED_DYNAMIC 1349 else if (do_dynamic_iosched && 1350 (bp->bio_cmd == BIO_WRITE || bp->bio_cmd == BIO_FLUSH)) { 1351 if (cam_iosched_sort_queue(isc)) 1352 bioq_disksort(&isc->write_queue, bp); 1353 else 1354 bioq_insert_tail(&isc->write_queue, bp); 1355 if (iosched_debug > 9) 1356 printf("Qw : %p %#x\n", bp, bp->bio_cmd); 1357 if (bp->bio_cmd == BIO_WRITE) { 1358 isc->write_stats.in++; 1359 isc->write_stats.queued++; 1360 } 1361 } 1362 #endif 1363 else { 1364 if (cam_iosched_sort_queue(isc)) 1365 bioq_disksort(&isc->bio_queue, bp); 1366 else 1367 bioq_insert_tail(&isc->bio_queue, bp); 1368 #ifdef CAM_IOSCHED_DYNAMIC 1369 if (iosched_debug > 9) 1370 printf("Qr : %p %#x\n", bp, bp->bio_cmd); 1371 if (bp->bio_cmd == BIO_READ) { 1372 isc->read_stats.in++; 1373 isc->read_stats.queued++; 1374 } else if (bp->bio_cmd == BIO_WRITE) { 1375 isc->write_stats.in++; 1376 isc->write_stats.queued++; 1377 } 1378 #endif 1379 } 1380 } 1381 1382 /* 1383 * If we have work, get it scheduled. Called with the periph lock held. 1384 */ 1385 void 1386 cam_iosched_schedule(struct cam_iosched_softc *isc, struct cam_periph *periph) 1387 { 1388 1389 if (cam_iosched_has_work(isc)) 1390 xpt_schedule(periph, CAM_PRIORITY_NORMAL); 1391 } 1392 1393 /* 1394 * Complete a trim request 1395 */ 1396 void 1397 cam_iosched_trim_done(struct cam_iosched_softc *isc) 1398 { 1399 1400 isc->flags &= ~CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1401 } 1402 1403 /* 1404 * Complete a bio. Called before we release the ccb with xpt_release_ccb so we 1405 * might use notes in the ccb for statistics. 1406 */ 1407 int 1408 cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp, 1409 union ccb *done_ccb) 1410 { 1411 int retval = 0; 1412 #ifdef CAM_IOSCHED_DYNAMIC 1413 if (!do_dynamic_iosched) 1414 return retval; 1415 1416 if (iosched_debug > 10) 1417 printf("done: %p %#x\n", bp, bp->bio_cmd); 1418 if (bp->bio_cmd == BIO_WRITE) { 1419 retval = cam_iosched_limiter_iodone(&isc->write_stats, bp); 1420 isc->write_stats.out++; 1421 isc->write_stats.pending--; 1422 } else if (bp->bio_cmd == BIO_READ) { 1423 retval = cam_iosched_limiter_iodone(&isc->read_stats, bp); 1424 isc->read_stats.out++; 1425 isc->read_stats.pending--; 1426 } else if (bp->bio_cmd == BIO_DELETE) { 1427 isc->trim_stats.out++; 1428 isc->trim_stats.pending--; 1429 } else if (bp->bio_cmd != BIO_FLUSH) { 1430 if (iosched_debug) 1431 printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd); 1432 } 1433 1434 if (!(bp->bio_flags & BIO_ERROR)) 1435 cam_iosched_io_metric_update(isc, done_ccb->ccb_h.qos.sim_data, 1436 bp->bio_cmd, bp->bio_bcount); 1437 #endif 1438 return retval; 1439 } 1440 1441 /* 1442 * Tell the io scheduler that you've pushed a trim down into the sim. 1443 * xxx better place for this? 1444 */ 1445 void 1446 cam_iosched_submit_trim(struct cam_iosched_softc *isc) 1447 { 1448 1449 isc->flags |= CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1450 } 1451 1452 /* 1453 * Change the sorting policy hint for I/O transactions for this device. 1454 */ 1455 void 1456 cam_iosched_set_sort_queue(struct cam_iosched_softc *isc, int val) 1457 { 1458 1459 isc->sort_io_queue = val; 1460 } 1461 1462 int 1463 cam_iosched_has_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1464 { 1465 return isc->flags & flags; 1466 } 1467 1468 void 1469 cam_iosched_set_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1470 { 1471 isc->flags |= flags; 1472 } 1473 1474 void 1475 cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1476 { 1477 isc->flags &= ~flags; 1478 } 1479 1480 #ifdef CAM_IOSCHED_DYNAMIC 1481 /* 1482 * After the method presented in Jack Crenshaw's 1998 article "Integer 1483 * Suqare Roots," reprinted at 1484 * http://www.embedded.com/electronics-blogs/programmer-s-toolbox/4219659/Integer-Square-Roots 1485 * and well worth the read. Briefly, we find the power of 4 that's the 1486 * largest smaller than val. We then check each smaller power of 4 to 1487 * see if val is still bigger. The right shifts at each step divide 1488 * the result by 2 which after successive application winds up 1489 * accumulating the right answer. It could also have been accumulated 1490 * using a separate root counter, but this code is smaller and faster 1491 * than that method. This method is also integer size invariant. 1492 * It returns floor(sqrt((float)val)), or the larget integer less than 1493 * or equal to the square root. 1494 */ 1495 static uint64_t 1496 isqrt64(uint64_t val) 1497 { 1498 uint64_t res = 0; 1499 uint64_t bit = 1ULL << (sizeof(uint64_t) * NBBY - 2); 1500 1501 /* 1502 * Find the largest power of 4 smaller than val. 1503 */ 1504 while (bit > val) 1505 bit >>= 2; 1506 1507 /* 1508 * Accumulate the answer, one bit at a time (we keep moving 1509 * them over since 2 is the square root of 4 and we test 1510 * powers of 4). We accumulate where we find the bit, but 1511 * the successive shifts land the bit in the right place 1512 * by the end. 1513 */ 1514 while (bit != 0) { 1515 if (val >= res + bit) { 1516 val -= res + bit; 1517 res = (res >> 1) + bit; 1518 } else 1519 res >>= 1; 1520 bit >>= 2; 1521 } 1522 1523 return res; 1524 } 1525 1526 /* 1527 * a and b are 32.32 fixed point stored in a 64-bit word. 1528 * Let al and bl be the .32 part of a and b. 1529 * Let ah and bh be the 32 part of a and b. 1530 * R is the radix and is 1 << 32 1531 * 1532 * a * b 1533 * (ah + al / R) * (bh + bl / R) 1534 * ah * bh + (al * bh + ah * bl) / R + al * bl / R^2 1535 * 1536 * After multiplicaiton, we have to renormalize by multiply by 1537 * R, so we wind up with 1538 * ah * bh * R + al * bh + ah * bl + al * bl / R 1539 * which turns out to be a very nice way to compute this value 1540 * so long as ah and bh are < 65536 there's no loss of high bits 1541 * and the low order bits are below the threshold of caring for 1542 * this application. 1543 */ 1544 static uint64_t 1545 mul(uint64_t a, uint64_t b) 1546 { 1547 uint64_t al, ah, bl, bh; 1548 al = a & 0xffffffff; 1549 ah = a >> 32; 1550 bl = b & 0xffffffff; 1551 bh = b >> 32; 1552 return ((ah * bh) << 32) + al * bh + ah * bl + ((al * bl) >> 32); 1553 } 1554 1555 static sbintime_t latencies[] = { 1556 SBT_1MS << 0, 1557 SBT_1MS << 1, 1558 SBT_1MS << 2, 1559 SBT_1MS << 3, 1560 SBT_1MS << 4, 1561 SBT_1MS << 5, 1562 SBT_1MS << 6, 1563 SBT_1MS << 7, 1564 SBT_1MS << 8, 1565 SBT_1MS << 9, 1566 SBT_1MS << 10 1567 }; 1568 1569 static void 1570 cam_iosched_update(struct iop_stats *iop, sbintime_t sim_latency) 1571 { 1572 sbintime_t y, yy; 1573 uint64_t var; 1574 int i; 1575 1576 /* 1577 * Keep counts for latency. We do it by power of two buckets. 1578 * This helps us spot outlier behavior obscured by averages. 1579 */ 1580 for (i = 0; i < LAT_BUCKETS - 1; i++) { 1581 if (sim_latency < latencies[i]) { 1582 iop->latencies[i]++; 1583 break; 1584 } 1585 } 1586 if (i == LAT_BUCKETS - 1) 1587 iop->latencies[i]++; /* Put all > 1024ms values into the last bucket. */ 1588 1589 /* 1590 * Classic expoentially decaying average with a tiny alpha 1591 * (2 ^ -alpha_bits). For more info see the NIST statistical 1592 * handbook. 1593 * 1594 * ema_t = y_t * alpha + ema_t-1 * (1 - alpha) 1595 * alpha = 1 / (1 << alpha_bits) 1596 * 1597 * Since alpha is a power of two, we can compute this w/o any mult or 1598 * division. 1599 */ 1600 y = sim_latency; 1601 iop->ema = (y + (iop->ema << alpha_bits) - iop->ema) >> alpha_bits; 1602 1603 yy = mul(y, y); 1604 iop->emss = (yy + (iop->emss << alpha_bits) - iop->emss) >> alpha_bits; 1605 1606 /* 1607 * s_1 = sum of data 1608 * s_2 = sum of data * data 1609 * ema ~ mean (or s_1 / N) 1610 * emss ~ s_2 / N 1611 * 1612 * sd = sqrt((N * s_2 - s_1 ^ 2) / (N * (N - 1))) 1613 * sd = sqrt((N * s_2 / N * (N - 1)) - (s_1 ^ 2 / (N * (N - 1)))) 1614 * 1615 * N ~ 2 / alpha - 1 1616 * alpha < 1 / 16 (typically much less) 1617 * N > 31 --> N large so N * (N - 1) is approx N * N 1618 * 1619 * substituting and rearranging: 1620 * sd ~ sqrt(s_2 / N - (s_1 / N) ^ 2) 1621 * ~ sqrt(emss - ema ^ 2); 1622 * which is the formula used here to get a decent estimate of sd which 1623 * we use to detect outliers. Note that when first starting up, it 1624 * takes a while for emss sum of squares estimator to converge on a 1625 * good value. during this time, it can be less than ema^2. We 1626 * compute a sd of 0 in that case, and ignore outliers. 1627 */ 1628 var = iop->emss - mul(iop->ema, iop->ema); 1629 iop->sd = (int64_t)var < 0 ? 0 : isqrt64(var); 1630 } 1631 1632 static void 1633 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 1634 sbintime_t sim_latency, int cmd, size_t size) 1635 { 1636 /* xxx Do we need to scale based on the size of the I/O ? */ 1637 switch (cmd) { 1638 case BIO_READ: 1639 cam_iosched_update(&isc->read_stats, sim_latency); 1640 break; 1641 case BIO_WRITE: 1642 cam_iosched_update(&isc->write_stats, sim_latency); 1643 break; 1644 case BIO_DELETE: 1645 cam_iosched_update(&isc->trim_stats, sim_latency); 1646 break; 1647 default: 1648 break; 1649 } 1650 } 1651 1652 #ifdef DDB 1653 static int biolen(struct bio_queue_head *bq) 1654 { 1655 int i = 0; 1656 struct bio *bp; 1657 1658 TAILQ_FOREACH(bp, &bq->queue, bio_queue) { 1659 i++; 1660 } 1661 return i; 1662 } 1663 1664 /* 1665 * Show the internal state of the I/O scheduler. 1666 */ 1667 DB_SHOW_COMMAND(iosched, cam_iosched_db_show) 1668 { 1669 struct cam_iosched_softc *isc; 1670 1671 if (!have_addr) { 1672 db_printf("Need addr\n"); 1673 return; 1674 } 1675 isc = (struct cam_iosched_softc *)addr; 1676 db_printf("pending_reads: %d\n", isc->read_stats.pending); 1677 db_printf("min_reads: %d\n", isc->read_stats.min); 1678 db_printf("max_reads: %d\n", isc->read_stats.max); 1679 db_printf("reads: %d\n", isc->read_stats.total); 1680 db_printf("in_reads: %d\n", isc->read_stats.in); 1681 db_printf("out_reads: %d\n", isc->read_stats.out); 1682 db_printf("queued_reads: %d\n", isc->read_stats.queued); 1683 db_printf("Current Q len %d\n", biolen(&isc->bio_queue)); 1684 db_printf("pending_writes: %d\n", isc->write_stats.pending); 1685 db_printf("min_writes: %d\n", isc->write_stats.min); 1686 db_printf("max_writes: %d\n", isc->write_stats.max); 1687 db_printf("writes: %d\n", isc->write_stats.total); 1688 db_printf("in_writes: %d\n", isc->write_stats.in); 1689 db_printf("out_writes: %d\n", isc->write_stats.out); 1690 db_printf("queued_writes: %d\n", isc->write_stats.queued); 1691 db_printf("Current Q len %d\n", biolen(&isc->write_queue)); 1692 db_printf("pending_trims: %d\n", isc->trim_stats.pending); 1693 db_printf("min_trims: %d\n", isc->trim_stats.min); 1694 db_printf("max_trims: %d\n", isc->trim_stats.max); 1695 db_printf("trims: %d\n", isc->trim_stats.total); 1696 db_printf("in_trims: %d\n", isc->trim_stats.in); 1697 db_printf("out_trims: %d\n", isc->trim_stats.out); 1698 db_printf("queued_trims: %d\n", isc->trim_stats.queued); 1699 db_printf("Current Q len %d\n", biolen(&isc->trim_queue)); 1700 db_printf("read_bias: %d\n", isc->read_bias); 1701 db_printf("current_read_bias: %d\n", isc->current_read_bias); 1702 db_printf("Trim active? %s\n", 1703 (isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) ? "yes" : "no"); 1704 } 1705 #endif 1706 #endif 1707