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 { 162 l_init_t *l_init; 163 l_tick_t *l_tick; 164 l_iop_t *l_iop; 165 l_iop_t *l_caniop; 166 l_iodone_t *l_iodone; 167 } limsw[] = 168 { 169 { /* none */ 170 .l_init = NULL, 171 .l_tick = NULL, 172 .l_iop = NULL, 173 .l_iodone= NULL, 174 }, 175 { /* queue_depth */ 176 .l_init = NULL, 177 .l_tick = NULL, 178 .l_caniop = cam_iosched_qd_caniop, 179 .l_iop = cam_iosched_qd_iop, 180 .l_iodone= cam_iosched_qd_iodone, 181 }, 182 { /* iops */ 183 .l_init = cam_iosched_iops_init, 184 .l_tick = cam_iosched_iops_tick, 185 .l_caniop = cam_iosched_iops_caniop, 186 .l_iop = cam_iosched_iops_iop, 187 .l_iodone= NULL, 188 }, 189 { /* bandwidth */ 190 .l_init = cam_iosched_bw_init, 191 .l_tick = cam_iosched_bw_tick, 192 .l_caniop = cam_iosched_bw_caniop, 193 .l_iop = cam_iosched_bw_iop, 194 .l_iodone= NULL, 195 }, 196 }; 197 198 struct iop_stats 199 { 200 /* 201 * sysctl state for this subnode. 202 */ 203 struct sysctl_ctx_list sysctl_ctx; 204 struct sysctl_oid *sysctl_tree; 205 206 /* 207 * Information about the current rate limiters, if any 208 */ 209 io_limiter limiter; /* How are I/Os being limited */ 210 int min; /* Low range of limit */ 211 int max; /* High range of limit */ 212 int current; /* Current rate limiter */ 213 int l_value1; /* per-limiter scratch value 1. */ 214 int l_value2; /* per-limiter scratch value 2. */ 215 216 217 /* 218 * Debug information about counts of I/Os that have gone through the 219 * scheduler. 220 */ 221 int pending; /* I/Os pending in the hardware */ 222 int queued; /* number currently in the queue */ 223 int total; /* Total for all time -- wraps */ 224 int in; /* number queued all time -- wraps */ 225 int out; /* number completed all time -- wraps */ 226 227 /* 228 * Statistics on different bits of the process. 229 */ 230 /* Exp Moving Average, see alpha_bits for more details */ 231 sbintime_t ema; 232 sbintime_t emss; /* Exp Moving sum of the squares */ 233 sbintime_t sd; /* Last computed sd */ 234 235 uint32_t state_flags; 236 #define IOP_RATE_LIMITED 1u 237 238 #define LAT_BUCKETS 12 /* < 1ms < 2ms ... 512ms < 1024ms > 1024ms */ 239 uint64_t latencies[LAT_BUCKETS]; 240 241 struct cam_iosched_softc *softc; 242 }; 243 244 245 typedef enum { 246 set_max = 0, /* current = max */ 247 read_latency, /* Steer read latency by throttling writes */ 248 cl_max /* Keep last */ 249 } control_type; 250 251 static const char *cam_iosched_control_type_names[] = 252 { "set_max", "read_latency" }; 253 254 struct control_loop 255 { 256 /* 257 * sysctl state for this subnode. 258 */ 259 struct sysctl_ctx_list sysctl_ctx; 260 struct sysctl_oid *sysctl_tree; 261 262 sbintime_t next_steer; /* Time of next steer */ 263 sbintime_t steer_interval; /* How often do we steer? */ 264 sbintime_t lolat; 265 sbintime_t hilat; 266 int alpha; 267 control_type type; /* What type of control? */ 268 int last_count; /* Last I/O count */ 269 270 struct cam_iosched_softc *softc; 271 }; 272 273 #endif 274 275 struct cam_iosched_softc 276 { 277 struct bio_queue_head bio_queue; 278 struct bio_queue_head trim_queue; 279 /* scheduler flags < 16, user flags >= 16 */ 280 uint32_t flags; 281 int sort_io_queue; 282 #ifdef CAM_IOSCHED_DYNAMIC 283 int read_bias; /* Read bias setting */ 284 int current_read_bias; /* Current read bias state */ 285 int total_ticks; 286 int load; /* EMA of 'load average' of disk / 2^16 */ 287 288 struct bio_queue_head write_queue; 289 struct iop_stats read_stats, write_stats, trim_stats; 290 struct sysctl_ctx_list sysctl_ctx; 291 struct sysctl_oid *sysctl_tree; 292 293 int quanta; /* Number of quanta per second */ 294 struct callout ticker; /* Callout for our quota system */ 295 struct cam_periph *periph; /* cam periph associated with this device */ 296 uint32_t this_frac; /* Fraction of a second (1024ths) for this tick */ 297 sbintime_t last_time; /* Last time we ticked */ 298 struct control_loop cl; 299 #endif 300 }; 301 302 #ifdef CAM_IOSCHED_DYNAMIC 303 /* 304 * helper functions to call the limsw functions. 305 */ 306 static int 307 cam_iosched_limiter_init(struct iop_stats *ios) 308 { 309 int lim = ios->limiter; 310 311 /* maybe this should be a kassert */ 312 if (lim < none || lim >= limiter_max) 313 return EINVAL; 314 315 if (limsw[lim].l_init) 316 return limsw[lim].l_init(ios); 317 318 return 0; 319 } 320 321 static int 322 cam_iosched_limiter_tick(struct iop_stats *ios) 323 { 324 int lim = ios->limiter; 325 326 /* maybe this should be a kassert */ 327 if (lim < none || lim >= limiter_max) 328 return EINVAL; 329 330 if (limsw[lim].l_tick) 331 return limsw[lim].l_tick(ios); 332 333 return 0; 334 } 335 336 static int 337 cam_iosched_limiter_iop(struct iop_stats *ios, struct bio *bp) 338 { 339 int lim = ios->limiter; 340 341 /* maybe this should be a kassert */ 342 if (lim < none || lim >= limiter_max) 343 return EINVAL; 344 345 if (limsw[lim].l_iop) 346 return limsw[lim].l_iop(ios, bp); 347 348 return 0; 349 } 350 351 static int 352 cam_iosched_limiter_caniop(struct iop_stats *ios, struct bio *bp) 353 { 354 int lim = ios->limiter; 355 356 /* maybe this should be a kassert */ 357 if (lim < none || lim >= limiter_max) 358 return EINVAL; 359 360 if (limsw[lim].l_caniop) 361 return limsw[lim].l_caniop(ios, bp); 362 363 return 0; 364 } 365 366 static int 367 cam_iosched_limiter_iodone(struct iop_stats *ios, struct bio *bp) 368 { 369 int lim = ios->limiter; 370 371 /* maybe this should be a kassert */ 372 if (lim < none || lim >= limiter_max) 373 return 0; 374 375 if (limsw[lim].l_iodone) 376 return limsw[lim].l_iodone(ios, bp); 377 378 return 0; 379 } 380 381 /* 382 * Functions to implement the different kinds of limiters 383 */ 384 385 static int 386 cam_iosched_qd_iop(struct iop_stats *ios, struct bio *bp) 387 { 388 389 if (ios->current <= 0 || ios->pending < ios->current) 390 return 0; 391 392 return EAGAIN; 393 } 394 395 static int 396 cam_iosched_qd_caniop(struct iop_stats *ios, struct bio *bp) 397 { 398 399 if (ios->current <= 0 || ios->pending < ios->current) 400 return 0; 401 402 return EAGAIN; 403 } 404 405 static int 406 cam_iosched_qd_iodone(struct iop_stats *ios, struct bio *bp) 407 { 408 409 if (ios->current <= 0 || ios->pending != ios->current) 410 return 0; 411 412 return 1; 413 } 414 415 static int 416 cam_iosched_iops_init(struct iop_stats *ios) 417 { 418 419 ios->l_value1 = ios->current / ios->softc->quanta; 420 if (ios->l_value1 <= 0) 421 ios->l_value1 = 1; 422 423 return 0; 424 } 425 426 static int 427 cam_iosched_iops_tick(struct iop_stats *ios) 428 { 429 430 ios->l_value1 = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16); 431 if (ios->l_value1 <= 0) 432 ios->l_value1 = 1; 433 434 return 0; 435 } 436 437 static int 438 cam_iosched_iops_caniop(struct iop_stats *ios, struct bio *bp) 439 { 440 441 /* 442 * So if we have any more IOPs left, allow it, 443 * otherwise wait. 444 */ 445 if (ios->l_value1 <= 0) 446 return EAGAIN; 447 return 0; 448 } 449 450 static int 451 cam_iosched_iops_iop(struct iop_stats *ios, struct bio *bp) 452 { 453 int rv; 454 455 rv = cam_iosched_limiter_caniop(ios, bp); 456 if (rv == 0) 457 ios->l_value1--; 458 459 return rv; 460 } 461 462 static int 463 cam_iosched_bw_init(struct iop_stats *ios) 464 { 465 466 /* ios->current is in kB/s, so scale to bytes */ 467 ios->l_value1 = ios->current * 1000 / ios->softc->quanta; 468 469 return 0; 470 } 471 472 static int 473 cam_iosched_bw_tick(struct iop_stats *ios) 474 { 475 int bw; 476 477 /* 478 * If we're in the hole for available quota from 479 * the last time, then add the quantum for this. 480 * If we have any left over from last quantum, 481 * then too bad, that's lost. Also, ios->current 482 * is in kB/s, so scale. 483 * 484 * We also allow up to 4 quanta of credits to 485 * accumulate to deal with burstiness. 4 is extremely 486 * arbitrary. 487 */ 488 bw = (int)((ios->current * 1000ull * (uint64_t)ios->softc->this_frac) >> 16); 489 if (ios->l_value1 < bw * 4) 490 ios->l_value1 += bw; 491 492 return 0; 493 } 494 495 static int 496 cam_iosched_bw_caniop(struct iop_stats *ios, struct bio *bp) 497 { 498 /* 499 * So if we have any more bw quota left, allow it, 500 * otherwise wait. Not, we'll go negative and that's 501 * OK. We'll just get a lettle less next quota. 502 * 503 * Note on going negative: that allows us to process 504 * requests in order better, since we won't allow 505 * shorter reads to get around the long one that we 506 * don't have the quota to do just yet. It also prevents 507 * starvation by being a little more permissive about 508 * what we let through this quantum (to prevent the 509 * starvation), at the cost of getting a little less 510 * next quantum. 511 */ 512 if (ios->l_value1 <= 0) 513 return EAGAIN; 514 515 516 return 0; 517 } 518 519 static int 520 cam_iosched_bw_iop(struct iop_stats *ios, struct bio *bp) 521 { 522 int rv; 523 524 rv = cam_iosched_limiter_caniop(ios, bp); 525 if (rv == 0) 526 ios->l_value1 -= bp->bio_length; 527 528 return rv; 529 } 530 531 static void cam_iosched_cl_maybe_steer(struct control_loop *clp); 532 533 static void 534 cam_iosched_ticker(void *arg) 535 { 536 struct cam_iosched_softc *isc = arg; 537 sbintime_t now, delta; 538 int pending; 539 540 callout_reset(&isc->ticker, hz / isc->quanta - 1, cam_iosched_ticker, isc); 541 542 now = sbinuptime(); 543 delta = now - isc->last_time; 544 isc->this_frac = (uint32_t)delta >> 16; /* Note: discards seconds -- should be 0 harmless if not */ 545 isc->last_time = now; 546 547 cam_iosched_cl_maybe_steer(&isc->cl); 548 549 cam_iosched_limiter_tick(&isc->read_stats); 550 cam_iosched_limiter_tick(&isc->write_stats); 551 cam_iosched_limiter_tick(&isc->trim_stats); 552 553 cam_iosched_schedule(isc, isc->periph); 554 555 /* 556 * isc->load is an EMA of the pending I/Os at each tick. The number of 557 * pending I/Os is the sum of the I/Os queued to the hardware, and those 558 * in the software queue that could be queued to the hardware if there 559 * were slots. 560 * 561 * ios_stats.pending is a count of requests in the SIM right now for 562 * each of these types of I/O. So the total pending count is the sum of 563 * these I/Os and the sum of the queued I/Os still in the software queue 564 * for those operations that aren't being rate limited at the moment. 565 * 566 * The reason for the rate limiting bit is because those I/Os 567 * aren't part of the software queued load (since we could 568 * give them to hardware, but choose not to). 569 * 570 * Note: due to a bug in counting pending TRIM in the device, we 571 * don't include them in this count. We count each BIO_DELETE in 572 * the pending count, but the periph drivers collapse them down 573 * into one TRIM command. That one trim command gets the completion 574 * so the counts get off. 575 */ 576 pending = isc->read_stats.pending + isc->write_stats.pending /* + isc->trim_stats.pending */; 577 pending += !!(isc->read_stats.state_flags & IOP_RATE_LIMITED) * isc->read_stats.queued + 578 !!(isc->write_stats.state_flags & IOP_RATE_LIMITED) * isc->write_stats.queued /* + 579 !!(isc->trim_stats.state_flags & IOP_RATE_LIMITED) * isc->trim_stats.queued */ ; 580 pending <<= 16; 581 pending /= isc->periph->path->device->ccbq.total_openings; 582 583 isc->load = (pending + (isc->load << 13) - isc->load) >> 13; /* see above: 13 -> 16139 / 200/s = ~81s ~1 minute */ 584 585 isc->total_ticks++; 586 } 587 588 589 static void 590 cam_iosched_cl_init(struct control_loop *clp, struct cam_iosched_softc *isc) 591 { 592 593 clp->next_steer = sbinuptime(); 594 clp->softc = isc; 595 clp->steer_interval = SBT_1S * 5; /* Let's start out steering every 5s */ 596 clp->lolat = 5 * SBT_1MS; 597 clp->hilat = 15 * SBT_1MS; 598 clp->alpha = 20; /* Alpha == gain. 20 = .2 */ 599 clp->type = set_max; 600 } 601 602 static void 603 cam_iosched_cl_maybe_steer(struct control_loop *clp) 604 { 605 struct cam_iosched_softc *isc; 606 sbintime_t now, lat; 607 int old; 608 609 isc = clp->softc; 610 now = isc->last_time; 611 if (now < clp->next_steer) 612 return; 613 614 clp->next_steer = now + clp->steer_interval; 615 switch (clp->type) { 616 case set_max: 617 if (isc->write_stats.current != isc->write_stats.max) 618 printf("Steering write from %d kBps to %d kBps\n", 619 isc->write_stats.current, isc->write_stats.max); 620 isc->read_stats.current = isc->read_stats.max; 621 isc->write_stats.current = isc->write_stats.max; 622 isc->trim_stats.current = isc->trim_stats.max; 623 break; 624 case read_latency: 625 old = isc->write_stats.current; 626 lat = isc->read_stats.ema; 627 /* 628 * Simple PLL-like engine. Since we're steering to a range for 629 * the SP (set point) that makes things a little more 630 * complicated. In addition, we're not directly controlling our 631 * PV (process variable), the read latency, but instead are 632 * manipulating the write bandwidth limit for our MV 633 * (manipulation variable), analysis of this code gets a bit 634 * messy. Also, the MV is a very noisy control surface for read 635 * latency since it is affected by many hidden processes inside 636 * the device which change how responsive read latency will be 637 * in reaction to changes in write bandwidth. Unlike the classic 638 * boiler control PLL. this may result in over-steering while 639 * the SSD takes its time to react to the new, lower load. This 640 * is why we use a relatively low alpha of between .1 and .25 to 641 * compensate for this effect. At .1, it takes ~22 steering 642 * intervals to back off by a factor of 10. At .2 it only takes 643 * ~10. At .25 it only takes ~8. However some preliminary data 644 * from the SSD drives suggests a reasponse time in 10's of 645 * seconds before latency drops regardless of the new write 646 * rate. Careful observation will be reqiured to tune this 647 * effectively. 648 * 649 * Also, when there's no read traffic, we jack up the write 650 * limit too regardless of the last read latency. 10 is 651 * somewhat arbitrary. 652 */ 653 if (lat < clp->lolat || isc->read_stats.total - clp->last_count < 10) 654 isc->write_stats.current = isc->write_stats.current * 655 (100 + clp->alpha) / 100; /* Scale up */ 656 else if (lat > clp->hilat) 657 isc->write_stats.current = isc->write_stats.current * 658 (100 - clp->alpha) / 100; /* Scale down */ 659 clp->last_count = isc->read_stats.total; 660 661 /* 662 * Even if we don't steer, per se, enforce the min/max limits as 663 * those may have changed. 664 */ 665 if (isc->write_stats.current < isc->write_stats.min) 666 isc->write_stats.current = isc->write_stats.min; 667 if (isc->write_stats.current > isc->write_stats.max) 668 isc->write_stats.current = isc->write_stats.max; 669 if (old != isc->write_stats.current && iosched_debug) 670 printf("Steering write from %d kBps to %d kBps due to latency of %jdus\n", 671 old, isc->write_stats.current, 672 (uintmax_t)((uint64_t)1000000 * (uint32_t)lat) >> 32); 673 break; 674 case cl_max: 675 break; 676 } 677 } 678 #endif 679 680 /* Trim or similar currently pending completion */ 681 #define CAM_IOSCHED_FLAG_TRIM_ACTIVE (1ul << 0) 682 /* Callout active, and needs to be torn down */ 683 #define CAM_IOSCHED_FLAG_CALLOUT_ACTIVE (1ul << 1) 684 685 /* Periph drivers set these flags to indicate work */ 686 #define CAM_IOSCHED_FLAG_WORK_FLAGS ((0xffffu) << 16) 687 688 #ifdef CAM_IOSCHED_DYNAMIC 689 static void 690 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 691 sbintime_t sim_latency, int cmd, size_t size); 692 #endif 693 694 static inline int 695 cam_iosched_has_flagged_work(struct cam_iosched_softc *isc) 696 { 697 return !!(isc->flags & CAM_IOSCHED_FLAG_WORK_FLAGS); 698 } 699 700 static inline int 701 cam_iosched_has_io(struct cam_iosched_softc *isc) 702 { 703 #ifdef CAM_IOSCHED_DYNAMIC 704 if (do_dynamic_iosched) { 705 struct bio *rbp = bioq_first(&isc->bio_queue); 706 struct bio *wbp = bioq_first(&isc->write_queue); 707 int can_write = wbp != NULL && 708 cam_iosched_limiter_caniop(&isc->write_stats, wbp) == 0; 709 int can_read = rbp != NULL && 710 cam_iosched_limiter_caniop(&isc->read_stats, rbp) == 0; 711 if (iosched_debug > 2) { 712 printf("can write %d: pending_writes %d max_writes %d\n", can_write, isc->write_stats.pending, isc->write_stats.max); 713 printf("can read %d: read_stats.pending %d max_reads %d\n", can_read, isc->read_stats.pending, isc->read_stats.max); 714 printf("Queued reads %d writes %d\n", isc->read_stats.queued, isc->write_stats.queued); 715 } 716 return can_read || can_write; 717 } 718 #endif 719 return bioq_first(&isc->bio_queue) != NULL; 720 } 721 722 static inline int 723 cam_iosched_has_more_trim(struct cam_iosched_softc *isc) 724 { 725 return !(isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) && 726 bioq_first(&isc->trim_queue); 727 } 728 729 #define cam_iosched_sort_queue(isc) ((isc)->sort_io_queue >= 0 ? \ 730 (isc)->sort_io_queue : cam_sort_io_queues) 731 732 733 static inline int 734 cam_iosched_has_work(struct cam_iosched_softc *isc) 735 { 736 #ifdef CAM_IOSCHED_DYNAMIC 737 if (iosched_debug > 2) 738 printf("has work: %d %d %d\n", cam_iosched_has_io(isc), 739 cam_iosched_has_more_trim(isc), 740 cam_iosched_has_flagged_work(isc)); 741 #endif 742 743 return cam_iosched_has_io(isc) || 744 cam_iosched_has_more_trim(isc) || 745 cam_iosched_has_flagged_work(isc); 746 } 747 748 #ifdef CAM_IOSCHED_DYNAMIC 749 static void 750 cam_iosched_iop_stats_init(struct cam_iosched_softc *isc, struct iop_stats *ios) 751 { 752 753 ios->limiter = none; 754 cam_iosched_limiter_init(ios); 755 ios->in = 0; 756 ios->max = 300000; 757 ios->min = 1; 758 ios->out = 0; 759 ios->pending = 0; 760 ios->queued = 0; 761 ios->total = 0; 762 ios->ema = 0; 763 ios->emss = 0; 764 ios->sd = 0; 765 ios->softc = isc; 766 } 767 768 static int 769 cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS) 770 { 771 char buf[16]; 772 struct iop_stats *ios; 773 struct cam_iosched_softc *isc; 774 int value, i, error; 775 const char *p; 776 777 ios = arg1; 778 isc = ios->softc; 779 value = ios->limiter; 780 if (value < none || value >= limiter_max) 781 p = "UNKNOWN"; 782 else 783 p = cam_iosched_limiter_names[value]; 784 785 strlcpy(buf, p, sizeof(buf)); 786 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 787 if (error != 0 || req->newptr == NULL) 788 return error; 789 790 cam_periph_lock(isc->periph); 791 792 for (i = none; i < limiter_max; i++) { 793 if (strcmp(buf, cam_iosched_limiter_names[i]) != 0) 794 continue; 795 ios->limiter = i; 796 error = cam_iosched_limiter_init(ios); 797 if (error != 0) { 798 ios->limiter = value; 799 cam_periph_unlock(isc->periph); 800 return error; 801 } 802 /* Note: disk load averate requires ticker to be always running */ 803 callout_reset(&isc->ticker, hz / isc->quanta - 1, cam_iosched_ticker, isc); 804 isc->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 805 806 cam_periph_unlock(isc->periph); 807 return 0; 808 } 809 810 cam_periph_unlock(isc->periph); 811 return EINVAL; 812 } 813 814 static int 815 cam_iosched_control_type_sysctl(SYSCTL_HANDLER_ARGS) 816 { 817 char buf[16]; 818 struct control_loop *clp; 819 struct cam_iosched_softc *isc; 820 int value, i, error; 821 const char *p; 822 823 clp = arg1; 824 isc = clp->softc; 825 value = clp->type; 826 if (value < none || value >= cl_max) 827 p = "UNKNOWN"; 828 else 829 p = cam_iosched_control_type_names[value]; 830 831 strlcpy(buf, p, sizeof(buf)); 832 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 833 if (error != 0 || req->newptr == NULL) 834 return error; 835 836 for (i = set_max; i < cl_max; i++) { 837 if (strcmp(buf, cam_iosched_control_type_names[i]) != 0) 838 continue; 839 cam_periph_lock(isc->periph); 840 clp->type = i; 841 cam_periph_unlock(isc->periph); 842 return 0; 843 } 844 845 return EINVAL; 846 } 847 848 static int 849 cam_iosched_sbintime_sysctl(SYSCTL_HANDLER_ARGS) 850 { 851 char buf[16]; 852 sbintime_t value; 853 int error; 854 uint64_t us; 855 856 value = *(sbintime_t *)arg1; 857 us = (uint64_t)value / SBT_1US; 858 snprintf(buf, sizeof(buf), "%ju", (intmax_t)us); 859 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 860 if (error != 0 || req->newptr == NULL) 861 return error; 862 us = strtoul(buf, NULL, 10); 863 if (us == 0) 864 return EINVAL; 865 *(sbintime_t *)arg1 = us * SBT_1US; 866 return 0; 867 } 868 869 static int 870 cam_iosched_sysctl_latencies(SYSCTL_HANDLER_ARGS) 871 { 872 int i, error; 873 struct sbuf sb; 874 uint64_t *latencies; 875 876 latencies = arg1; 877 sbuf_new_for_sysctl(&sb, NULL, LAT_BUCKETS * 16, req); 878 879 for (i = 0; i < LAT_BUCKETS - 1; i++) 880 sbuf_printf(&sb, "%jd,", (intmax_t)latencies[i]); 881 sbuf_printf(&sb, "%jd", (intmax_t)latencies[LAT_BUCKETS - 1]); 882 error = sbuf_finish(&sb); 883 sbuf_delete(&sb); 884 885 return (error); 886 } 887 888 static void 889 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct iop_stats *ios, char *name) 890 { 891 struct sysctl_oid_list *n; 892 struct sysctl_ctx_list *ctx; 893 894 ios->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 895 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, name, 896 CTLFLAG_RD, 0, name); 897 n = SYSCTL_CHILDREN(ios->sysctl_tree); 898 ctx = &ios->sysctl_ctx; 899 900 SYSCTL_ADD_UQUAD(ctx, n, 901 OID_AUTO, "ema", CTLFLAG_RD, 902 &ios->ema, 903 "Fast Exponentially Weighted Moving Average"); 904 SYSCTL_ADD_UQUAD(ctx, n, 905 OID_AUTO, "emss", CTLFLAG_RD, 906 &ios->emss, 907 "Fast Exponentially Weighted Moving Sum of Squares (maybe wrong)"); 908 SYSCTL_ADD_UQUAD(ctx, n, 909 OID_AUTO, "sd", CTLFLAG_RD, 910 &ios->sd, 911 "Estimated SD for fast ema (may be wrong)"); 912 913 SYSCTL_ADD_INT(ctx, n, 914 OID_AUTO, "pending", CTLFLAG_RD, 915 &ios->pending, 0, 916 "Instantaneous # of pending transactions"); 917 SYSCTL_ADD_INT(ctx, n, 918 OID_AUTO, "count", CTLFLAG_RD, 919 &ios->total, 0, 920 "# of transactions submitted to hardware"); 921 SYSCTL_ADD_INT(ctx, n, 922 OID_AUTO, "queued", CTLFLAG_RD, 923 &ios->queued, 0, 924 "# of transactions in the queue"); 925 SYSCTL_ADD_INT(ctx, n, 926 OID_AUTO, "in", CTLFLAG_RD, 927 &ios->in, 0, 928 "# of transactions queued to driver"); 929 SYSCTL_ADD_INT(ctx, n, 930 OID_AUTO, "out", CTLFLAG_RD, 931 &ios->out, 0, 932 "# of transactions completed"); 933 934 SYSCTL_ADD_PROC(ctx, n, 935 OID_AUTO, "limiter", CTLTYPE_STRING | CTLFLAG_RW, 936 ios, 0, cam_iosched_limiter_sysctl, "A", 937 "Current limiting type."); 938 SYSCTL_ADD_INT(ctx, n, 939 OID_AUTO, "min", CTLFLAG_RW, 940 &ios->min, 0, 941 "min resource"); 942 SYSCTL_ADD_INT(ctx, n, 943 OID_AUTO, "max", CTLFLAG_RW, 944 &ios->max, 0, 945 "max resource"); 946 SYSCTL_ADD_INT(ctx, n, 947 OID_AUTO, "current", CTLFLAG_RW, 948 &ios->current, 0, 949 "current resource"); 950 951 SYSCTL_ADD_PROC(ctx, n, 952 OID_AUTO, "latencies", CTLTYPE_STRING | CTLFLAG_RD, 953 &ios->latencies, 0, 954 cam_iosched_sysctl_latencies, "A", 955 "Array of power of 2 latency from 1ms to 1.024s"); 956 } 957 958 static void 959 cam_iosched_iop_stats_fini(struct iop_stats *ios) 960 { 961 if (ios->sysctl_tree) 962 if (sysctl_ctx_free(&ios->sysctl_ctx) != 0) 963 printf("can't remove iosched sysctl stats context\n"); 964 } 965 966 static void 967 cam_iosched_cl_sysctl_init(struct cam_iosched_softc *isc) 968 { 969 struct sysctl_oid_list *n; 970 struct sysctl_ctx_list *ctx; 971 struct control_loop *clp; 972 973 clp = &isc->cl; 974 clp->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 975 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, "control", 976 CTLFLAG_RD, 0, "Control loop info"); 977 n = SYSCTL_CHILDREN(clp->sysctl_tree); 978 ctx = &clp->sysctl_ctx; 979 980 SYSCTL_ADD_PROC(ctx, n, 981 OID_AUTO, "type", CTLTYPE_STRING | CTLFLAG_RW, 982 clp, 0, cam_iosched_control_type_sysctl, "A", 983 "Control loop algorithm"); 984 SYSCTL_ADD_PROC(ctx, n, 985 OID_AUTO, "steer_interval", CTLTYPE_STRING | CTLFLAG_RW, 986 &clp->steer_interval, 0, cam_iosched_sbintime_sysctl, "A", 987 "How often to steer (in us)"); 988 SYSCTL_ADD_PROC(ctx, n, 989 OID_AUTO, "lolat", CTLTYPE_STRING | CTLFLAG_RW, 990 &clp->lolat, 0, cam_iosched_sbintime_sysctl, "A", 991 "Low water mark for Latency (in us)"); 992 SYSCTL_ADD_PROC(ctx, n, 993 OID_AUTO, "hilat", CTLTYPE_STRING | CTLFLAG_RW, 994 &clp->hilat, 0, cam_iosched_sbintime_sysctl, "A", 995 "Hi water mark for Latency (in us)"); 996 SYSCTL_ADD_INT(ctx, n, 997 OID_AUTO, "alpha", CTLFLAG_RW, 998 &clp->alpha, 0, 999 "Alpha for PLL (x100) aka gain"); 1000 } 1001 1002 static void 1003 cam_iosched_cl_sysctl_fini(struct control_loop *clp) 1004 { 1005 if (clp->sysctl_tree) 1006 if (sysctl_ctx_free(&clp->sysctl_ctx) != 0) 1007 printf("can't remove iosched sysctl control loop context\n"); 1008 } 1009 #endif 1010 1011 /* 1012 * Allocate the iosched structure. This also insulates callers from knowing 1013 * sizeof struct cam_iosched_softc. 1014 */ 1015 int 1016 cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph) 1017 { 1018 1019 *iscp = malloc(sizeof(**iscp), M_CAMSCHED, M_NOWAIT | M_ZERO); 1020 if (*iscp == NULL) 1021 return ENOMEM; 1022 #ifdef CAM_IOSCHED_DYNAMIC 1023 if (iosched_debug) 1024 printf("CAM IOSCHEDULER Allocating entry at %p\n", *iscp); 1025 #endif 1026 (*iscp)->sort_io_queue = -1; 1027 bioq_init(&(*iscp)->bio_queue); 1028 bioq_init(&(*iscp)->trim_queue); 1029 #ifdef CAM_IOSCHED_DYNAMIC 1030 if (do_dynamic_iosched) { 1031 bioq_init(&(*iscp)->write_queue); 1032 (*iscp)->read_bias = 100; 1033 (*iscp)->current_read_bias = 100; 1034 (*iscp)->quanta = 200; 1035 cam_iosched_iop_stats_init(*iscp, &(*iscp)->read_stats); 1036 cam_iosched_iop_stats_init(*iscp, &(*iscp)->write_stats); 1037 cam_iosched_iop_stats_init(*iscp, &(*iscp)->trim_stats); 1038 (*iscp)->trim_stats.max = 1; /* Trims are special: one at a time for now */ 1039 (*iscp)->last_time = sbinuptime(); 1040 callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0); 1041 (*iscp)->periph = periph; 1042 cam_iosched_cl_init(&(*iscp)->cl, *iscp); 1043 callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta - 1, cam_iosched_ticker, *iscp); 1044 (*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1045 } 1046 #endif 1047 1048 return 0; 1049 } 1050 1051 /* 1052 * Reclaim all used resources. This assumes that other folks have 1053 * drained the requests in the hardware. Maybe an unwise assumption. 1054 */ 1055 void 1056 cam_iosched_fini(struct cam_iosched_softc *isc) 1057 { 1058 if (isc) { 1059 cam_iosched_flush(isc, NULL, ENXIO); 1060 #ifdef CAM_IOSCHED_DYNAMIC 1061 cam_iosched_iop_stats_fini(&isc->read_stats); 1062 cam_iosched_iop_stats_fini(&isc->write_stats); 1063 cam_iosched_iop_stats_fini(&isc->trim_stats); 1064 cam_iosched_cl_sysctl_fini(&isc->cl); 1065 if (isc->sysctl_tree) 1066 if (sysctl_ctx_free(&isc->sysctl_ctx) != 0) 1067 printf("can't remove iosched sysctl stats context\n"); 1068 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) { 1069 callout_drain(&isc->ticker); 1070 isc->flags &= ~ CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1071 } 1072 1073 #endif 1074 free(isc, M_CAMSCHED); 1075 } 1076 } 1077 1078 /* 1079 * After we're sure we're attaching a device, go ahead and add 1080 * hooks for any sysctl we may wish to honor. 1081 */ 1082 void cam_iosched_sysctl_init(struct cam_iosched_softc *isc, 1083 struct sysctl_ctx_list *ctx, struct sysctl_oid *node) 1084 { 1085 #ifdef CAM_IOSCHED_DYNAMIC 1086 struct sysctl_oid_list *n; 1087 #endif 1088 1089 SYSCTL_ADD_INT(ctx, SYSCTL_CHILDREN(node), 1090 OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE, 1091 &isc->sort_io_queue, 0, 1092 "Sort IO queue to try and optimise disk access patterns"); 1093 1094 #ifdef CAM_IOSCHED_DYNAMIC 1095 if (!do_dynamic_iosched) 1096 return; 1097 1098 isc->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1099 SYSCTL_CHILDREN(node), OID_AUTO, "iosched", 1100 CTLFLAG_RD, 0, "I/O scheduler statistics"); 1101 n = SYSCTL_CHILDREN(isc->sysctl_tree); 1102 ctx = &isc->sysctl_ctx; 1103 1104 cam_iosched_iop_stats_sysctl_init(isc, &isc->read_stats, "read"); 1105 cam_iosched_iop_stats_sysctl_init(isc, &isc->write_stats, "write"); 1106 cam_iosched_iop_stats_sysctl_init(isc, &isc->trim_stats, "trim"); 1107 cam_iosched_cl_sysctl_init(isc); 1108 1109 SYSCTL_ADD_INT(ctx, n, 1110 OID_AUTO, "read_bias", CTLFLAG_RW, 1111 &isc->read_bias, 100, 1112 "How biased towards read should we be independent of limits"); 1113 1114 SYSCTL_ADD_INT(ctx, n, 1115 OID_AUTO, "quanta", CTLFLAG_RW, 1116 &isc->quanta, 200, 1117 "How many quanta per second do we slice the I/O up into"); 1118 1119 SYSCTL_ADD_INT(ctx, n, 1120 OID_AUTO, "total_ticks", CTLFLAG_RD, 1121 &isc->total_ticks, 0, 1122 "Total number of ticks we've done"); 1123 1124 SYSCTL_ADD_INT(ctx, n, 1125 OID_AUTO, "load", CTLFLAG_RD, 1126 &isc->load, 0, 1127 "scaled load average / 100"); 1128 #endif 1129 } 1130 1131 /* 1132 * Flush outstanding I/O. Consumers of this library don't know all the 1133 * queues we may keep, so this allows all I/O to be flushed in one 1134 * convenient call. 1135 */ 1136 void 1137 cam_iosched_flush(struct cam_iosched_softc *isc, struct devstat *stp, int err) 1138 { 1139 bioq_flush(&isc->bio_queue, stp, err); 1140 bioq_flush(&isc->trim_queue, stp, err); 1141 #ifdef CAM_IOSCHED_DYNAMIC 1142 if (do_dynamic_iosched) 1143 bioq_flush(&isc->write_queue, stp, err); 1144 #endif 1145 } 1146 1147 #ifdef CAM_IOSCHED_DYNAMIC 1148 static struct bio * 1149 cam_iosched_get_write(struct cam_iosched_softc *isc) 1150 { 1151 struct bio *bp; 1152 1153 /* 1154 * We control the write rate by controlling how many requests we send 1155 * down to the drive at any one time. Fewer requests limits the 1156 * effects of both starvation when the requests take a while and write 1157 * amplification when each request is causing more than one write to 1158 * the NAND media. Limiting the queue depth like this will also limit 1159 * the write throughput and give and reads that want to compete to 1160 * compete unfairly. 1161 */ 1162 bp = bioq_first(&isc->write_queue); 1163 if (bp == NULL) { 1164 if (iosched_debug > 3) 1165 printf("No writes present in write_queue\n"); 1166 return NULL; 1167 } 1168 1169 /* 1170 * If pending read, prefer that based on current read bias 1171 * setting. 1172 */ 1173 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) { 1174 if (iosched_debug) 1175 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); 1176 isc->current_read_bias--; 1177 /* We're not limiting writes, per se, just doing reads first */ 1178 return NULL; 1179 } 1180 1181 /* 1182 * See if our current limiter allows this I/O. 1183 */ 1184 if (cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) { 1185 if (iosched_debug) 1186 printf("Can't write because limiter says no.\n"); 1187 isc->write_stats.state_flags |= IOP_RATE_LIMITED; 1188 return NULL; 1189 } 1190 1191 /* 1192 * Let's do this: We've passed all the gates and we're a go 1193 * to schedule the I/O in the SIM. 1194 */ 1195 isc->current_read_bias = isc->read_bias; 1196 bioq_remove(&isc->write_queue, bp); 1197 if (bp->bio_cmd == BIO_WRITE) { 1198 isc->write_stats.queued--; 1199 isc->write_stats.total++; 1200 isc->write_stats.pending++; 1201 } 1202 if (iosched_debug > 9) 1203 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1204 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED; 1205 return bp; 1206 } 1207 #endif 1208 1209 /* 1210 * Put back a trim that you weren't able to actually schedule this time. 1211 */ 1212 void 1213 cam_iosched_put_back_trim(struct cam_iosched_softc *isc, struct bio *bp) 1214 { 1215 bioq_insert_head(&isc->trim_queue, bp); 1216 #ifdef CAM_IOSCHED_DYNAMIC 1217 isc->trim_stats.queued++; 1218 isc->trim_stats.total--; /* since we put it back, don't double count */ 1219 isc->trim_stats.pending--; 1220 #endif 1221 } 1222 1223 /* 1224 * gets the next trim from the trim queue. 1225 * 1226 * Assumes we're called with the periph lock held. It removes this 1227 * trim from the queue and the device must explicitly reinstert it 1228 * should the need arise. 1229 */ 1230 struct bio * 1231 cam_iosched_next_trim(struct cam_iosched_softc *isc) 1232 { 1233 struct bio *bp; 1234 1235 bp = bioq_first(&isc->trim_queue); 1236 if (bp == NULL) 1237 return NULL; 1238 bioq_remove(&isc->trim_queue, bp); 1239 #ifdef CAM_IOSCHED_DYNAMIC 1240 isc->trim_stats.queued--; 1241 isc->trim_stats.total++; 1242 isc->trim_stats.pending++; 1243 #endif 1244 return bp; 1245 } 1246 1247 /* 1248 * gets the an available trim from the trim queue, if there's no trim 1249 * already pending. It removes this trim from the queue and the device 1250 * must explicitly reinstert it should the need arise. 1251 * 1252 * Assumes we're called with the periph lock held. 1253 */ 1254 struct bio * 1255 cam_iosched_get_trim(struct cam_iosched_softc *isc) 1256 { 1257 1258 if (!cam_iosched_has_more_trim(isc)) 1259 return NULL; 1260 1261 return cam_iosched_next_trim(isc); 1262 } 1263 1264 /* 1265 * Determine what the next bit of work to do is for the periph. The 1266 * default implementation looks to see if we have trims to do, but no 1267 * trims outstanding. If so, we do that. Otherwise we see if we have 1268 * other work. If we do, then we do that. Otherwise why were we called? 1269 */ 1270 struct bio * 1271 cam_iosched_next_bio(struct cam_iosched_softc *isc) 1272 { 1273 struct bio *bp; 1274 1275 /* 1276 * See if we have a trim that can be scheduled. We can only send one 1277 * at a time down, so this takes that into account. 1278 * 1279 * XXX newer TRIM commands are queueable. Revisit this when we 1280 * implement them. 1281 */ 1282 if ((bp = cam_iosched_get_trim(isc)) != NULL) 1283 return bp; 1284 1285 #ifdef CAM_IOSCHED_DYNAMIC 1286 /* 1287 * See if we have any pending writes, and room in the queue for them, 1288 * and if so, those are next. 1289 */ 1290 if (do_dynamic_iosched) { 1291 if ((bp = cam_iosched_get_write(isc)) != NULL) 1292 return bp; 1293 } 1294 #endif 1295 1296 /* 1297 * next, see if there's other, normal I/O waiting. If so return that. 1298 */ 1299 if ((bp = bioq_first(&isc->bio_queue)) == NULL) 1300 return NULL; 1301 1302 #ifdef CAM_IOSCHED_DYNAMIC 1303 /* 1304 * For the dynamic scheduler, bio_queue is only for reads, so enforce 1305 * the limits here. Enforce only for reads. 1306 */ 1307 if (do_dynamic_iosched) { 1308 if (bp->bio_cmd == BIO_READ && 1309 cam_iosched_limiter_iop(&isc->read_stats, bp) != 0) { 1310 isc->read_stats.state_flags |= IOP_RATE_LIMITED; 1311 return NULL; 1312 } 1313 } 1314 isc->read_stats.state_flags &= ~IOP_RATE_LIMITED; 1315 #endif 1316 bioq_remove(&isc->bio_queue, bp); 1317 #ifdef CAM_IOSCHED_DYNAMIC 1318 if (do_dynamic_iosched) { 1319 if (bp->bio_cmd == BIO_READ) { 1320 isc->read_stats.queued--; 1321 isc->read_stats.total++; 1322 isc->read_stats.pending++; 1323 } else 1324 printf("Found bio_cmd = %#x\n", bp->bio_cmd); 1325 } 1326 if (iosched_debug > 9) 1327 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1328 #endif 1329 return bp; 1330 } 1331 1332 /* 1333 * Driver has been given some work to do by the block layer. Tell the 1334 * scheduler about it and have it queue the work up. The scheduler module 1335 * will then return the currently most useful bit of work later, possibly 1336 * deferring work for various reasons. 1337 */ 1338 void 1339 cam_iosched_queue_work(struct cam_iosched_softc *isc, struct bio *bp) 1340 { 1341 1342 /* 1343 * Put all trims on the trim queue sorted, since we know 1344 * that the collapsing code requires this. Otherwise put 1345 * the work on the bio queue. 1346 */ 1347 if (bp->bio_cmd == BIO_DELETE) { 1348 bioq_disksort(&isc->trim_queue, bp); 1349 #ifdef CAM_IOSCHED_DYNAMIC 1350 isc->trim_stats.in++; 1351 isc->trim_stats.queued++; 1352 #endif 1353 } 1354 #ifdef CAM_IOSCHED_DYNAMIC 1355 else if (do_dynamic_iosched && 1356 (bp->bio_cmd == BIO_WRITE || bp->bio_cmd == BIO_FLUSH)) { 1357 if (cam_iosched_sort_queue(isc)) 1358 bioq_disksort(&isc->write_queue, bp); 1359 else 1360 bioq_insert_tail(&isc->write_queue, bp); 1361 if (iosched_debug > 9) 1362 printf("Qw : %p %#x\n", bp, bp->bio_cmd); 1363 if (bp->bio_cmd == BIO_WRITE) { 1364 isc->write_stats.in++; 1365 isc->write_stats.queued++; 1366 } 1367 } 1368 #endif 1369 else { 1370 if (cam_iosched_sort_queue(isc)) 1371 bioq_disksort(&isc->bio_queue, bp); 1372 else 1373 bioq_insert_tail(&isc->bio_queue, bp); 1374 #ifdef CAM_IOSCHED_DYNAMIC 1375 if (iosched_debug > 9) 1376 printf("Qr : %p %#x\n", bp, bp->bio_cmd); 1377 if (bp->bio_cmd == BIO_READ) { 1378 isc->read_stats.in++; 1379 isc->read_stats.queued++; 1380 } else if (bp->bio_cmd == BIO_WRITE) { 1381 isc->write_stats.in++; 1382 isc->write_stats.queued++; 1383 } 1384 #endif 1385 } 1386 } 1387 1388 /* 1389 * If we have work, get it scheduled. Called with the periph lock held. 1390 */ 1391 void 1392 cam_iosched_schedule(struct cam_iosched_softc *isc, struct cam_periph *periph) 1393 { 1394 1395 if (cam_iosched_has_work(isc)) 1396 xpt_schedule(periph, CAM_PRIORITY_NORMAL); 1397 } 1398 1399 /* 1400 * Complete a trim request 1401 */ 1402 void 1403 cam_iosched_trim_done(struct cam_iosched_softc *isc) 1404 { 1405 1406 isc->flags &= ~CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1407 } 1408 1409 /* 1410 * Complete a bio. Called before we release the ccb with xpt_release_ccb so we 1411 * might use notes in the ccb for statistics. 1412 */ 1413 int 1414 cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp, 1415 union ccb *done_ccb) 1416 { 1417 int retval = 0; 1418 #ifdef CAM_IOSCHED_DYNAMIC 1419 if (!do_dynamic_iosched) 1420 return retval; 1421 1422 if (iosched_debug > 10) 1423 printf("done: %p %#x\n", bp, bp->bio_cmd); 1424 if (bp->bio_cmd == BIO_WRITE) { 1425 retval = cam_iosched_limiter_iodone(&isc->write_stats, bp); 1426 isc->write_stats.out++; 1427 isc->write_stats.pending--; 1428 } else if (bp->bio_cmd == BIO_READ) { 1429 retval = cam_iosched_limiter_iodone(&isc->read_stats, bp); 1430 isc->read_stats.out++; 1431 isc->read_stats.pending--; 1432 } else if (bp->bio_cmd == BIO_DELETE) { 1433 isc->trim_stats.out++; 1434 isc->trim_stats.pending--; 1435 } else if (bp->bio_cmd != BIO_FLUSH) { 1436 if (iosched_debug) 1437 printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd); 1438 } 1439 1440 if (!(bp->bio_flags & BIO_ERROR)) 1441 cam_iosched_io_metric_update(isc, done_ccb->ccb_h.qos.sim_data, 1442 bp->bio_cmd, bp->bio_bcount); 1443 #endif 1444 return retval; 1445 } 1446 1447 /* 1448 * Tell the io scheduler that you've pushed a trim down into the sim. 1449 * xxx better place for this? 1450 */ 1451 void 1452 cam_iosched_submit_trim(struct cam_iosched_softc *isc) 1453 { 1454 1455 isc->flags |= CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1456 } 1457 1458 /* 1459 * Change the sorting policy hint for I/O transactions for this device. 1460 */ 1461 void 1462 cam_iosched_set_sort_queue(struct cam_iosched_softc *isc, int val) 1463 { 1464 1465 isc->sort_io_queue = val; 1466 } 1467 1468 int 1469 cam_iosched_has_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1470 { 1471 return isc->flags & flags; 1472 } 1473 1474 void 1475 cam_iosched_set_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1476 { 1477 isc->flags |= flags; 1478 } 1479 1480 void 1481 cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1482 { 1483 isc->flags &= ~flags; 1484 } 1485 1486 #ifdef CAM_IOSCHED_DYNAMIC 1487 /* 1488 * After the method presented in Jack Crenshaw's 1998 article "Integer 1489 * Suqare Roots," reprinted at 1490 * http://www.embedded.com/electronics-blogs/programmer-s-toolbox/4219659/Integer-Square-Roots 1491 * and well worth the read. Briefly, we find the power of 4 that's the 1492 * largest smaller than val. We then check each smaller power of 4 to 1493 * see if val is still bigger. The right shifts at each step divide 1494 * the result by 2 which after successive application winds up 1495 * accumulating the right answer. It could also have been accumulated 1496 * using a separate root counter, but this code is smaller and faster 1497 * than that method. This method is also integer size invariant. 1498 * It returns floor(sqrt((float)val)), or the larget integer less than 1499 * or equal to the square root. 1500 */ 1501 static uint64_t 1502 isqrt64(uint64_t val) 1503 { 1504 uint64_t res = 0; 1505 uint64_t bit = 1ULL << (sizeof(uint64_t) * NBBY - 2); 1506 1507 /* 1508 * Find the largest power of 4 smaller than val. 1509 */ 1510 while (bit > val) 1511 bit >>= 2; 1512 1513 /* 1514 * Accumulate the answer, one bit at a time (we keep moving 1515 * them over since 2 is the square root of 4 and we test 1516 * powers of 4). We accumulate where we find the bit, but 1517 * the successive shifts land the bit in the right place 1518 * by the end. 1519 */ 1520 while (bit != 0) { 1521 if (val >= res + bit) { 1522 val -= res + bit; 1523 res = (res >> 1) + bit; 1524 } else 1525 res >>= 1; 1526 bit >>= 2; 1527 } 1528 1529 return res; 1530 } 1531 1532 /* 1533 * a and b are 32.32 fixed point stored in a 64-bit word. 1534 * Let al and bl be the .32 part of a and b. 1535 * Let ah and bh be the 32 part of a and b. 1536 * R is the radix and is 1 << 32 1537 * 1538 * a * b 1539 * (ah + al / R) * (bh + bl / R) 1540 * ah * bh + (al * bh + ah * bl) / R + al * bl / R^2 1541 * 1542 * After multiplicaiton, we have to renormalize by multiply by 1543 * R, so we wind up with 1544 * ah * bh * R + al * bh + ah * bl + al * bl / R 1545 * which turns out to be a very nice way to compute this value 1546 * so long as ah and bh are < 65536 there's no loss of high bits 1547 * and the low order bits are below the threshold of caring for 1548 * this application. 1549 */ 1550 static uint64_t 1551 mul(uint64_t a, uint64_t b) 1552 { 1553 uint64_t al, ah, bl, bh; 1554 al = a & 0xffffffff; 1555 ah = a >> 32; 1556 bl = b & 0xffffffff; 1557 bh = b >> 32; 1558 return ((ah * bh) << 32) + al * bh + ah * bl + ((al * bl) >> 32); 1559 } 1560 1561 static sbintime_t latencies[] = { 1562 SBT_1MS << 0, 1563 SBT_1MS << 1, 1564 SBT_1MS << 2, 1565 SBT_1MS << 3, 1566 SBT_1MS << 4, 1567 SBT_1MS << 5, 1568 SBT_1MS << 6, 1569 SBT_1MS << 7, 1570 SBT_1MS << 8, 1571 SBT_1MS << 9, 1572 SBT_1MS << 10 1573 }; 1574 1575 static void 1576 cam_iosched_update(struct iop_stats *iop, sbintime_t sim_latency) 1577 { 1578 sbintime_t y, yy; 1579 uint64_t var; 1580 int i; 1581 1582 /* 1583 * Keep counts for latency. We do it by power of two buckets. 1584 * This helps us spot outlier behavior obscured by averages. 1585 */ 1586 for (i = 0; i < LAT_BUCKETS - 1; i++) { 1587 if (sim_latency < latencies[i]) { 1588 iop->latencies[i]++; 1589 break; 1590 } 1591 } 1592 if (i == LAT_BUCKETS - 1) 1593 iop->latencies[i]++; /* Put all > 1024ms values into the last bucket. */ 1594 1595 /* 1596 * Classic expoentially decaying average with a tiny alpha 1597 * (2 ^ -alpha_bits). For more info see the NIST statistical 1598 * handbook. 1599 * 1600 * ema_t = y_t * alpha + ema_t-1 * (1 - alpha) 1601 * alpha = 1 / (1 << alpha_bits) 1602 * 1603 * Since alpha is a power of two, we can compute this w/o any mult or 1604 * division. 1605 */ 1606 y = sim_latency; 1607 iop->ema = (y + (iop->ema << alpha_bits) - iop->ema) >> alpha_bits; 1608 1609 yy = mul(y, y); 1610 iop->emss = (yy + (iop->emss << alpha_bits) - iop->emss) >> alpha_bits; 1611 1612 /* 1613 * s_1 = sum of data 1614 * s_2 = sum of data * data 1615 * ema ~ mean (or s_1 / N) 1616 * emss ~ s_2 / N 1617 * 1618 * sd = sqrt((N * s_2 - s_1 ^ 2) / (N * (N - 1))) 1619 * sd = sqrt((N * s_2 / N * (N - 1)) - (s_1 ^ 2 / (N * (N - 1)))) 1620 * 1621 * N ~ 2 / alpha - 1 1622 * alpha < 1 / 16 (typically much less) 1623 * N > 31 --> N large so N * (N - 1) is approx N * N 1624 * 1625 * substituting and rearranging: 1626 * sd ~ sqrt(s_2 / N - (s_1 / N) ^ 2) 1627 * ~ sqrt(emss - ema ^ 2); 1628 * which is the formula used here to get a decent estimate of sd which 1629 * we use to detect outliers. Note that when first starting up, it 1630 * takes a while for emss sum of squares estimator to converge on a 1631 * good value. during this time, it can be less than ema^2. We 1632 * compute a sd of 0 in that case, and ignore outliers. 1633 */ 1634 var = iop->emss - mul(iop->ema, iop->ema); 1635 iop->sd = (int64_t)var < 0 ? 0 : isqrt64(var); 1636 } 1637 1638 #ifdef CAM_IOSCHED_DYNAMIC 1639 static void 1640 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 1641 sbintime_t sim_latency, int cmd, size_t size) 1642 { 1643 /* xxx Do we need to scale based on the size of the I/O ? */ 1644 switch (cmd) { 1645 case BIO_READ: 1646 cam_iosched_update(&isc->read_stats, sim_latency); 1647 break; 1648 case BIO_WRITE: 1649 cam_iosched_update(&isc->write_stats, sim_latency); 1650 break; 1651 case BIO_DELETE: 1652 cam_iosched_update(&isc->trim_stats, sim_latency); 1653 break; 1654 default: 1655 break; 1656 } 1657 } 1658 #endif 1659 1660 #ifdef DDB 1661 static int biolen(struct bio_queue_head *bq) 1662 { 1663 int i = 0; 1664 struct bio *bp; 1665 1666 TAILQ_FOREACH(bp, &bq->queue, bio_queue) { 1667 i++; 1668 } 1669 return i; 1670 } 1671 1672 /* 1673 * Show the internal state of the I/O scheduler. 1674 */ 1675 DB_SHOW_COMMAND(iosched, cam_iosched_db_show) 1676 { 1677 struct cam_iosched_softc *isc; 1678 1679 if (!have_addr) { 1680 db_printf("Need addr\n"); 1681 return; 1682 } 1683 isc = (struct cam_iosched_softc *)addr; 1684 db_printf("pending_reads: %d\n", isc->read_stats.pending); 1685 db_printf("min_reads: %d\n", isc->read_stats.min); 1686 db_printf("max_reads: %d\n", isc->read_stats.max); 1687 db_printf("reads: %d\n", isc->read_stats.total); 1688 db_printf("in_reads: %d\n", isc->read_stats.in); 1689 db_printf("out_reads: %d\n", isc->read_stats.out); 1690 db_printf("queued_reads: %d\n", isc->read_stats.queued); 1691 db_printf("Current Q len %d\n", biolen(&isc->bio_queue)); 1692 db_printf("pending_writes: %d\n", isc->write_stats.pending); 1693 db_printf("min_writes: %d\n", isc->write_stats.min); 1694 db_printf("max_writes: %d\n", isc->write_stats.max); 1695 db_printf("writes: %d\n", isc->write_stats.total); 1696 db_printf("in_writes: %d\n", isc->write_stats.in); 1697 db_printf("out_writes: %d\n", isc->write_stats.out); 1698 db_printf("queued_writes: %d\n", isc->write_stats.queued); 1699 db_printf("Current Q len %d\n", biolen(&isc->write_queue)); 1700 db_printf("pending_trims: %d\n", isc->trim_stats.pending); 1701 db_printf("min_trims: %d\n", isc->trim_stats.min); 1702 db_printf("max_trims: %d\n", isc->trim_stats.max); 1703 db_printf("trims: %d\n", isc->trim_stats.total); 1704 db_printf("in_trims: %d\n", isc->trim_stats.in); 1705 db_printf("out_trims: %d\n", isc->trim_stats.out); 1706 db_printf("queued_trims: %d\n", isc->trim_stats.queued); 1707 db_printf("Current Q len %d\n", biolen(&isc->trim_queue)); 1708 db_printf("read_bias: %d\n", isc->read_bias); 1709 db_printf("current_read_bias: %d\n", isc->current_read_bias); 1710 db_printf("Trim active? %s\n", 1711 (isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) ? "yes" : "no"); 1712 } 1713 #endif 1714 #endif 1715