1 /*- 2 * CAM IO Scheduler Interface 3 * 4 * Copyright (c) 2015 Netflix, Inc. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions, and the following disclaimer, 12 * without modification, immediately at the beginning of the file. 13 * 2. The name of the author may not be used to endorse or promote products 14 * derived from this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR 20 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 * 28 * $FreeBSD$ 29 */ 30 31 #include "opt_cam.h" 32 #include "opt_ddb.h" 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include <sys/param.h> 38 39 #include <sys/systm.h> 40 #include <sys/kernel.h> 41 #include <sys/bio.h> 42 #include <sys/lock.h> 43 #include <sys/malloc.h> 44 #include <sys/mutex.h> 45 #include <sys/sbuf.h> 46 #include <sys/sysctl.h> 47 48 #include <cam/cam.h> 49 #include <cam/cam_ccb.h> 50 #include <cam/cam_periph.h> 51 #include <cam/cam_xpt_periph.h> 52 #include <cam/cam_xpt_internal.h> 53 #include <cam/cam_iosched.h> 54 55 #include <ddb/ddb.h> 56 57 static MALLOC_DEFINE(M_CAMSCHED, "CAM I/O Scheduler", 58 "CAM I/O Scheduler buffers"); 59 60 /* 61 * Default I/O scheduler for FreeBSD. This implementation is just a thin-vineer 62 * over the bioq_* interface, with notions of separate calls for normal I/O and 63 * for trims. 64 * 65 * When CAM_IOSCHED_DYNAMIC is defined, the scheduler is enhanced to dynamically 66 * steer the rate of one type of traffic to help other types of traffic (eg 67 * limit writes when read latency deteriorates on SSDs). 68 */ 69 70 #ifdef CAM_IOSCHED_DYNAMIC 71 72 static int do_dynamic_iosched = 1; 73 TUNABLE_INT("kern.cam.do_dynamic_iosched", &do_dynamic_iosched); 74 SYSCTL_INT(_kern_cam, OID_AUTO, do_dynamic_iosched, CTLFLAG_RD, 75 &do_dynamic_iosched, 1, 76 "Enable Dynamic I/O scheduler optimizations."); 77 78 /* 79 * For an EMA, with an alpha of alpha, we know 80 * alpha = 2 / (N + 1) 81 * or 82 * N = 1 + (2 / alpha) 83 * where N is the number of samples that 86% of the current 84 * EMA is derived from. 85 * 86 * So we invent[*] alpha_bits: 87 * alpha_bits = -log_2(alpha) 88 * alpha = 2^-alpha_bits 89 * So 90 * N = 1 + 2^(alpha_bits + 1) 91 * 92 * The default 9 gives a 1025 lookback for 86% of the data. 93 * For a brief intro: https://en.wikipedia.org/wiki/Moving_average 94 * 95 * [*] Steal from the load average code and many other places. 96 * Note: See computation of EMA and EMVAR for acceptable ranges of alpha. 97 */ 98 static int alpha_bits = 9; 99 TUNABLE_INT("kern.cam.iosched_alpha_bits", &alpha_bits); 100 SYSCTL_INT(_kern_cam, OID_AUTO, iosched_alpha_bits, CTLFLAG_RW, 101 &alpha_bits, 1, 102 "Bits in EMA's alpha."); 103 104 struct iop_stats; 105 struct cam_iosched_softc; 106 107 int iosched_debug = 0; 108 109 typedef enum { 110 none = 0, /* No limits */ 111 queue_depth, /* Limit how many ops we queue to SIM */ 112 iops, /* Limit # of IOPS to the drive */ 113 bandwidth, /* Limit bandwidth to the drive */ 114 limiter_max 115 } io_limiter; 116 117 static const char *cam_iosched_limiter_names[] = 118 { "none", "queue_depth", "iops", "bandwidth" }; 119 120 /* 121 * Called to initialize the bits of the iop_stats structure relevant to the 122 * limiter. Called just after the limiter is set. 123 */ 124 typedef int l_init_t(struct iop_stats *); 125 126 /* 127 * Called every tick. 128 */ 129 typedef int l_tick_t(struct iop_stats *); 130 131 /* 132 * Called to see if the limiter thinks this IOP can be allowed to 133 * proceed. If so, the limiter assumes that the IOP proceeded 134 * and makes any accounting of it that's needed. 135 */ 136 typedef int l_iop_t(struct iop_stats *, struct bio *); 137 138 /* 139 * Called when an I/O completes so the limiter can update its 140 * accounting. Pending I/Os may complete in any order (even when 141 * sent to the hardware at the same time), so the limiter may not 142 * make any assumptions other than this I/O has completed. If it 143 * returns 1, then xpt_schedule() needs to be called again. 144 */ 145 typedef int l_iodone_t(struct iop_stats *, struct bio *); 146 147 static l_iop_t cam_iosched_qd_iop; 148 static l_iop_t cam_iosched_qd_caniop; 149 static l_iodone_t cam_iosched_qd_iodone; 150 151 static l_init_t cam_iosched_iops_init; 152 static l_tick_t cam_iosched_iops_tick; 153 static l_iop_t cam_iosched_iops_caniop; 154 static l_iop_t cam_iosched_iops_iop; 155 156 static l_init_t cam_iosched_bw_init; 157 static l_tick_t cam_iosched_bw_tick; 158 static l_iop_t cam_iosched_bw_caniop; 159 static l_iop_t cam_iosched_bw_iop; 160 161 struct limswitch { 162 l_init_t *l_init; 163 l_tick_t *l_tick; 164 l_iop_t *l_iop; 165 l_iop_t *l_caniop; 166 l_iodone_t *l_iodone; 167 } limsw[] = 168 { 169 { /* none */ 170 .l_init = NULL, 171 .l_tick = NULL, 172 .l_iop = NULL, 173 .l_iodone= NULL, 174 }, 175 { /* queue_depth */ 176 .l_init = NULL, 177 .l_tick = NULL, 178 .l_caniop = cam_iosched_qd_caniop, 179 .l_iop = cam_iosched_qd_iop, 180 .l_iodone= cam_iosched_qd_iodone, 181 }, 182 { /* iops */ 183 .l_init = cam_iosched_iops_init, 184 .l_tick = cam_iosched_iops_tick, 185 .l_caniop = cam_iosched_iops_caniop, 186 .l_iop = cam_iosched_iops_iop, 187 .l_iodone= NULL, 188 }, 189 { /* bandwidth */ 190 .l_init = cam_iosched_bw_init, 191 .l_tick = cam_iosched_bw_tick, 192 .l_caniop = cam_iosched_bw_caniop, 193 .l_iop = cam_iosched_bw_iop, 194 .l_iodone= NULL, 195 }, 196 }; 197 198 struct iop_stats { 199 /* 200 * sysctl state for this subnode. 201 */ 202 struct sysctl_ctx_list sysctl_ctx; 203 struct sysctl_oid *sysctl_tree; 204 205 /* 206 * Information about the current rate limiters, if any 207 */ 208 io_limiter limiter; /* How are I/Os being limited */ 209 int min; /* Low range of limit */ 210 int max; /* High range of limit */ 211 int current; /* Current rate limiter */ 212 int l_value1; /* per-limiter scratch value 1. */ 213 int l_value2; /* per-limiter scratch value 2. */ 214 215 /* 216 * Debug information about counts of I/Os that have gone through the 217 * scheduler. 218 */ 219 int pending; /* I/Os pending in the hardware */ 220 int queued; /* number currently in the queue */ 221 int total; /* Total for all time -- wraps */ 222 int in; /* number queued all time -- wraps */ 223 int out; /* number completed all time -- wraps */ 224 225 /* 226 * Statistics on different bits of the process. 227 */ 228 /* Exp Moving Average, see alpha_bits for more details */ 229 sbintime_t ema; 230 sbintime_t emvar; 231 sbintime_t sd; /* Last computed sd */ 232 233 uint32_t state_flags; 234 #define IOP_RATE_LIMITED 1u 235 236 #define LAT_BUCKETS 15 /* < 1ms < 2ms ... < 2^(n-1)ms >= 2^(n-1)ms*/ 237 uint64_t latencies[LAT_BUCKETS]; 238 239 struct cam_iosched_softc *softc; 240 }; 241 242 243 typedef enum { 244 set_max = 0, /* current = max */ 245 read_latency, /* Steer read latency by throttling writes */ 246 cl_max /* Keep last */ 247 } control_type; 248 249 static const char *cam_iosched_control_type_names[] = 250 { "set_max", "read_latency" }; 251 252 struct control_loop { 253 /* 254 * sysctl state for this subnode. 255 */ 256 struct sysctl_ctx_list sysctl_ctx; 257 struct sysctl_oid *sysctl_tree; 258 259 sbintime_t next_steer; /* Time of next steer */ 260 sbintime_t steer_interval; /* How often do we steer? */ 261 sbintime_t lolat; 262 sbintime_t hilat; 263 int alpha; 264 control_type type; /* What type of control? */ 265 int last_count; /* Last I/O count */ 266 267 struct cam_iosched_softc *softc; 268 }; 269 270 #endif 271 272 struct cam_iosched_softc { 273 struct bio_queue_head bio_queue; 274 struct bio_queue_head trim_queue; 275 /* scheduler flags < 16, user flags >= 16 */ 276 uint32_t flags; 277 int sort_io_queue; 278 #ifdef CAM_IOSCHED_DYNAMIC 279 int read_bias; /* Read bias setting */ 280 int current_read_bias; /* Current read bias state */ 281 int total_ticks; 282 int load; /* EMA of 'load average' of disk / 2^16 */ 283 284 struct bio_queue_head write_queue; 285 struct iop_stats read_stats, write_stats, trim_stats; 286 struct sysctl_ctx_list sysctl_ctx; 287 struct sysctl_oid *sysctl_tree; 288 289 int quanta; /* Number of quanta per second */ 290 struct callout ticker; /* Callout for our quota system */ 291 struct cam_periph *periph; /* cam periph associated with this device */ 292 uint32_t this_frac; /* Fraction of a second (1024ths) for this tick */ 293 sbintime_t last_time; /* Last time we ticked */ 294 struct control_loop cl; 295 #endif 296 }; 297 298 #ifdef CAM_IOSCHED_DYNAMIC 299 /* 300 * helper functions to call the limsw functions. 301 */ 302 static int 303 cam_iosched_limiter_init(struct iop_stats *ios) 304 { 305 int lim = ios->limiter; 306 307 /* maybe this should be a kassert */ 308 if (lim < none || lim >= limiter_max) 309 return EINVAL; 310 311 if (limsw[lim].l_init) 312 return limsw[lim].l_init(ios); 313 314 return 0; 315 } 316 317 static int 318 cam_iosched_limiter_tick(struct iop_stats *ios) 319 { 320 int lim = ios->limiter; 321 322 /* maybe this should be a kassert */ 323 if (lim < none || lim >= limiter_max) 324 return EINVAL; 325 326 if (limsw[lim].l_tick) 327 return limsw[lim].l_tick(ios); 328 329 return 0; 330 } 331 332 static int 333 cam_iosched_limiter_iop(struct iop_stats *ios, struct bio *bp) 334 { 335 int lim = ios->limiter; 336 337 /* maybe this should be a kassert */ 338 if (lim < none || lim >= limiter_max) 339 return EINVAL; 340 341 if (limsw[lim].l_iop) 342 return limsw[lim].l_iop(ios, bp); 343 344 return 0; 345 } 346 347 static int 348 cam_iosched_limiter_caniop(struct iop_stats *ios, struct bio *bp) 349 { 350 int lim = ios->limiter; 351 352 /* maybe this should be a kassert */ 353 if (lim < none || lim >= limiter_max) 354 return EINVAL; 355 356 if (limsw[lim].l_caniop) 357 return limsw[lim].l_caniop(ios, bp); 358 359 return 0; 360 } 361 362 static int 363 cam_iosched_limiter_iodone(struct iop_stats *ios, struct bio *bp) 364 { 365 int lim = ios->limiter; 366 367 /* maybe this should be a kassert */ 368 if (lim < none || lim >= limiter_max) 369 return 0; 370 371 if (limsw[lim].l_iodone) 372 return limsw[lim].l_iodone(ios, bp); 373 374 return 0; 375 } 376 377 /* 378 * Functions to implement the different kinds of limiters 379 */ 380 381 static int 382 cam_iosched_qd_iop(struct iop_stats *ios, struct bio *bp) 383 { 384 385 if (ios->current <= 0 || ios->pending < ios->current) 386 return 0; 387 388 return EAGAIN; 389 } 390 391 static int 392 cam_iosched_qd_caniop(struct iop_stats *ios, struct bio *bp) 393 { 394 395 if (ios->current <= 0 || ios->pending < ios->current) 396 return 0; 397 398 return EAGAIN; 399 } 400 401 static int 402 cam_iosched_qd_iodone(struct iop_stats *ios, struct bio *bp) 403 { 404 405 if (ios->current <= 0 || ios->pending != ios->current) 406 return 0; 407 408 return 1; 409 } 410 411 static int 412 cam_iosched_iops_init(struct iop_stats *ios) 413 { 414 415 ios->l_value1 = ios->current / ios->softc->quanta; 416 if (ios->l_value1 <= 0) 417 ios->l_value1 = 1; 418 ios->l_value2 = 0; 419 420 return 0; 421 } 422 423 static int 424 cam_iosched_iops_tick(struct iop_stats *ios) 425 { 426 int new_ios; 427 428 /* 429 * Allow at least one IO per tick until all 430 * the IOs for this interval have been spent. 431 */ 432 new_ios = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16); 433 if (new_ios < 1 && ios->l_value2 < ios->current) { 434 new_ios = 1; 435 ios->l_value2++; 436 } 437 438 /* 439 * If this a new accounting interval, discard any "unspent" ios 440 * granted in the previous interval. Otherwise add the new ios to 441 * the previously granted ones that haven't been spent yet. 442 */ 443 if ((ios->softc->total_ticks % ios->softc->quanta) == 0) { 444 ios->l_value1 = new_ios; 445 ios->l_value2 = 1; 446 } else { 447 ios->l_value1 += new_ios; 448 } 449 450 451 return 0; 452 } 453 454 static int 455 cam_iosched_iops_caniop(struct iop_stats *ios, struct bio *bp) 456 { 457 458 /* 459 * So if we have any more IOPs left, allow it, 460 * otherwise wait. 461 */ 462 if (ios->l_value1 <= 0) 463 return EAGAIN; 464 return 0; 465 } 466 467 static int 468 cam_iosched_iops_iop(struct iop_stats *ios, struct bio *bp) 469 { 470 int rv; 471 472 rv = cam_iosched_limiter_caniop(ios, bp); 473 if (rv == 0) 474 ios->l_value1--; 475 476 return rv; 477 } 478 479 static int 480 cam_iosched_bw_init(struct iop_stats *ios) 481 { 482 483 /* ios->current is in kB/s, so scale to bytes */ 484 ios->l_value1 = ios->current * 1000 / ios->softc->quanta; 485 486 return 0; 487 } 488 489 static int 490 cam_iosched_bw_tick(struct iop_stats *ios) 491 { 492 int bw; 493 494 /* 495 * If we're in the hole for available quota from 496 * the last time, then add the quantum for this. 497 * If we have any left over from last quantum, 498 * then too bad, that's lost. Also, ios->current 499 * is in kB/s, so scale. 500 * 501 * We also allow up to 4 quanta of credits to 502 * accumulate to deal with burstiness. 4 is extremely 503 * arbitrary. 504 */ 505 bw = (int)((ios->current * 1000ull * (uint64_t)ios->softc->this_frac) >> 16); 506 if (ios->l_value1 < bw * 4) 507 ios->l_value1 += bw; 508 509 return 0; 510 } 511 512 static int 513 cam_iosched_bw_caniop(struct iop_stats *ios, struct bio *bp) 514 { 515 /* 516 * So if we have any more bw quota left, allow it, 517 * otherwise wait. Note, we'll go negative and that's 518 * OK. We'll just get a little less next quota. 519 * 520 * Note on going negative: that allows us to process 521 * requests in order better, since we won't allow 522 * shorter reads to get around the long one that we 523 * don't have the quota to do just yet. It also prevents 524 * starvation by being a little more permissive about 525 * what we let through this quantum (to prevent the 526 * starvation), at the cost of getting a little less 527 * next quantum. 528 */ 529 if (ios->l_value1 <= 0) 530 return EAGAIN; 531 532 533 return 0; 534 } 535 536 static int 537 cam_iosched_bw_iop(struct iop_stats *ios, struct bio *bp) 538 { 539 int rv; 540 541 rv = cam_iosched_limiter_caniop(ios, bp); 542 if (rv == 0) 543 ios->l_value1 -= bp->bio_length; 544 545 return rv; 546 } 547 548 static void cam_iosched_cl_maybe_steer(struct control_loop *clp); 549 550 static void 551 cam_iosched_ticker(void *arg) 552 { 553 struct cam_iosched_softc *isc = arg; 554 sbintime_t now, delta; 555 int pending; 556 557 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc); 558 559 now = sbinuptime(); 560 delta = now - isc->last_time; 561 isc->this_frac = (uint32_t)delta >> 16; /* Note: discards seconds -- should be 0 harmless if not */ 562 isc->last_time = now; 563 564 cam_iosched_cl_maybe_steer(&isc->cl); 565 566 cam_iosched_limiter_tick(&isc->read_stats); 567 cam_iosched_limiter_tick(&isc->write_stats); 568 cam_iosched_limiter_tick(&isc->trim_stats); 569 570 cam_iosched_schedule(isc, isc->periph); 571 572 /* 573 * isc->load is an EMA of the pending I/Os at each tick. The number of 574 * pending I/Os is the sum of the I/Os queued to the hardware, and those 575 * in the software queue that could be queued to the hardware if there 576 * were slots. 577 * 578 * ios_stats.pending is a count of requests in the SIM right now for 579 * each of these types of I/O. So the total pending count is the sum of 580 * these I/Os and the sum of the queued I/Os still in the software queue 581 * for those operations that aren't being rate limited at the moment. 582 * 583 * The reason for the rate limiting bit is because those I/Os 584 * aren't part of the software queued load (since we could 585 * give them to hardware, but choose not to). 586 * 587 * Note: due to a bug in counting pending TRIM in the device, we 588 * don't include them in this count. We count each BIO_DELETE in 589 * the pending count, but the periph drivers collapse them down 590 * into one TRIM command. That one trim command gets the completion 591 * so the counts get off. 592 */ 593 pending = isc->read_stats.pending + isc->write_stats.pending /* + isc->trim_stats.pending */; 594 pending += !!(isc->read_stats.state_flags & IOP_RATE_LIMITED) * isc->read_stats.queued + 595 !!(isc->write_stats.state_flags & IOP_RATE_LIMITED) * isc->write_stats.queued /* + 596 !!(isc->trim_stats.state_flags & IOP_RATE_LIMITED) * isc->trim_stats.queued */ ; 597 pending <<= 16; 598 pending /= isc->periph->path->device->ccbq.total_openings; 599 600 isc->load = (pending + (isc->load << 13) - isc->load) >> 13; /* see above: 13 -> 16139 / 200/s = ~81s ~1 minute */ 601 602 isc->total_ticks++; 603 } 604 605 606 static void 607 cam_iosched_cl_init(struct control_loop *clp, struct cam_iosched_softc *isc) 608 { 609 610 clp->next_steer = sbinuptime(); 611 clp->softc = isc; 612 clp->steer_interval = SBT_1S * 5; /* Let's start out steering every 5s */ 613 clp->lolat = 5 * SBT_1MS; 614 clp->hilat = 15 * SBT_1MS; 615 clp->alpha = 20; /* Alpha == gain. 20 = .2 */ 616 clp->type = set_max; 617 } 618 619 static void 620 cam_iosched_cl_maybe_steer(struct control_loop *clp) 621 { 622 struct cam_iosched_softc *isc; 623 sbintime_t now, lat; 624 int old; 625 626 isc = clp->softc; 627 now = isc->last_time; 628 if (now < clp->next_steer) 629 return; 630 631 clp->next_steer = now + clp->steer_interval; 632 switch (clp->type) { 633 case set_max: 634 if (isc->write_stats.current != isc->write_stats.max) 635 printf("Steering write from %d kBps to %d kBps\n", 636 isc->write_stats.current, isc->write_stats.max); 637 isc->read_stats.current = isc->read_stats.max; 638 isc->write_stats.current = isc->write_stats.max; 639 isc->trim_stats.current = isc->trim_stats.max; 640 break; 641 case read_latency: 642 old = isc->write_stats.current; 643 lat = isc->read_stats.ema; 644 /* 645 * Simple PLL-like engine. Since we're steering to a range for 646 * the SP (set point) that makes things a little more 647 * complicated. In addition, we're not directly controlling our 648 * PV (process variable), the read latency, but instead are 649 * manipulating the write bandwidth limit for our MV 650 * (manipulation variable), analysis of this code gets a bit 651 * messy. Also, the MV is a very noisy control surface for read 652 * latency since it is affected by many hidden processes inside 653 * the device which change how responsive read latency will be 654 * in reaction to changes in write bandwidth. Unlike the classic 655 * boiler control PLL. this may result in over-steering while 656 * the SSD takes its time to react to the new, lower load. This 657 * is why we use a relatively low alpha of between .1 and .25 to 658 * compensate for this effect. At .1, it takes ~22 steering 659 * intervals to back off by a factor of 10. At .2 it only takes 660 * ~10. At .25 it only takes ~8. However some preliminary data 661 * from the SSD drives suggests a reasponse time in 10's of 662 * seconds before latency drops regardless of the new write 663 * rate. Careful observation will be required to tune this 664 * effectively. 665 * 666 * Also, when there's no read traffic, we jack up the write 667 * limit too regardless of the last read latency. 10 is 668 * somewhat arbitrary. 669 */ 670 if (lat < clp->lolat || isc->read_stats.total - clp->last_count < 10) 671 isc->write_stats.current = isc->write_stats.current * 672 (100 + clp->alpha) / 100; /* Scale up */ 673 else if (lat > clp->hilat) 674 isc->write_stats.current = isc->write_stats.current * 675 (100 - clp->alpha) / 100; /* Scale down */ 676 clp->last_count = isc->read_stats.total; 677 678 /* 679 * Even if we don't steer, per se, enforce the min/max limits as 680 * those may have changed. 681 */ 682 if (isc->write_stats.current < isc->write_stats.min) 683 isc->write_stats.current = isc->write_stats.min; 684 if (isc->write_stats.current > isc->write_stats.max) 685 isc->write_stats.current = isc->write_stats.max; 686 if (old != isc->write_stats.current && iosched_debug) 687 printf("Steering write from %d kBps to %d kBps due to latency of %jdus\n", 688 old, isc->write_stats.current, 689 (uintmax_t)((uint64_t)1000000 * (uint32_t)lat) >> 32); 690 break; 691 case cl_max: 692 break; 693 } 694 } 695 #endif 696 697 /* 698 * Trim or similar currently pending completion. Should only be set for 699 * those drivers wishing only one Trim active at a time. 700 */ 701 #define CAM_IOSCHED_FLAG_TRIM_ACTIVE (1ul << 0) 702 /* Callout active, and needs to be torn down */ 703 #define CAM_IOSCHED_FLAG_CALLOUT_ACTIVE (1ul << 1) 704 705 /* Periph drivers set these flags to indicate work */ 706 #define CAM_IOSCHED_FLAG_WORK_FLAGS ((0xffffu) << 16) 707 708 #ifdef CAM_IOSCHED_DYNAMIC 709 static void 710 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 711 sbintime_t sim_latency, int cmd, size_t size); 712 #endif 713 714 static inline int 715 cam_iosched_has_flagged_work(struct cam_iosched_softc *isc) 716 { 717 return !!(isc->flags & CAM_IOSCHED_FLAG_WORK_FLAGS); 718 } 719 720 static inline int 721 cam_iosched_has_io(struct cam_iosched_softc *isc) 722 { 723 #ifdef CAM_IOSCHED_DYNAMIC 724 if (do_dynamic_iosched) { 725 struct bio *rbp = bioq_first(&isc->bio_queue); 726 struct bio *wbp = bioq_first(&isc->write_queue); 727 int can_write = wbp != NULL && 728 cam_iosched_limiter_caniop(&isc->write_stats, wbp) == 0; 729 int can_read = rbp != NULL && 730 cam_iosched_limiter_caniop(&isc->read_stats, rbp) == 0; 731 if (iosched_debug > 2) { 732 printf("can write %d: pending_writes %d max_writes %d\n", can_write, isc->write_stats.pending, isc->write_stats.max); 733 printf("can read %d: read_stats.pending %d max_reads %d\n", can_read, isc->read_stats.pending, isc->read_stats.max); 734 printf("Queued reads %d writes %d\n", isc->read_stats.queued, isc->write_stats.queued); 735 } 736 return can_read || can_write; 737 } 738 #endif 739 return bioq_first(&isc->bio_queue) != NULL; 740 } 741 742 static inline int 743 cam_iosched_has_more_trim(struct cam_iosched_softc *isc) 744 { 745 return !(isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) && 746 bioq_first(&isc->trim_queue); 747 } 748 749 #define cam_iosched_sort_queue(isc) ((isc)->sort_io_queue >= 0 ? \ 750 (isc)->sort_io_queue : cam_sort_io_queues) 751 752 753 static inline int 754 cam_iosched_has_work(struct cam_iosched_softc *isc) 755 { 756 #ifdef CAM_IOSCHED_DYNAMIC 757 if (iosched_debug > 2) 758 printf("has work: %d %d %d\n", cam_iosched_has_io(isc), 759 cam_iosched_has_more_trim(isc), 760 cam_iosched_has_flagged_work(isc)); 761 #endif 762 763 return cam_iosched_has_io(isc) || 764 cam_iosched_has_more_trim(isc) || 765 cam_iosched_has_flagged_work(isc); 766 } 767 768 #ifdef CAM_IOSCHED_DYNAMIC 769 static void 770 cam_iosched_iop_stats_init(struct cam_iosched_softc *isc, struct iop_stats *ios) 771 { 772 773 ios->limiter = none; 774 ios->in = 0; 775 ios->max = ios->current = 300000; 776 ios->min = 1; 777 ios->out = 0; 778 ios->pending = 0; 779 ios->queued = 0; 780 ios->total = 0; 781 ios->ema = 0; 782 ios->emvar = 0; 783 ios->softc = isc; 784 cam_iosched_limiter_init(ios); 785 } 786 787 static int 788 cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS) 789 { 790 char buf[16]; 791 struct iop_stats *ios; 792 struct cam_iosched_softc *isc; 793 int value, i, error; 794 const char *p; 795 796 ios = arg1; 797 isc = ios->softc; 798 value = ios->limiter; 799 if (value < none || value >= limiter_max) 800 p = "UNKNOWN"; 801 else 802 p = cam_iosched_limiter_names[value]; 803 804 strlcpy(buf, p, sizeof(buf)); 805 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 806 if (error != 0 || req->newptr == NULL) 807 return error; 808 809 cam_periph_lock(isc->periph); 810 811 for (i = none; i < limiter_max; i++) { 812 if (strcmp(buf, cam_iosched_limiter_names[i]) != 0) 813 continue; 814 ios->limiter = i; 815 error = cam_iosched_limiter_init(ios); 816 if (error != 0) { 817 ios->limiter = value; 818 cam_periph_unlock(isc->periph); 819 return error; 820 } 821 /* Note: disk load averate requires ticker to be always running */ 822 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc); 823 isc->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 824 825 cam_periph_unlock(isc->periph); 826 return 0; 827 } 828 829 cam_periph_unlock(isc->periph); 830 return EINVAL; 831 } 832 833 static int 834 cam_iosched_control_type_sysctl(SYSCTL_HANDLER_ARGS) 835 { 836 char buf[16]; 837 struct control_loop *clp; 838 struct cam_iosched_softc *isc; 839 int value, i, error; 840 const char *p; 841 842 clp = arg1; 843 isc = clp->softc; 844 value = clp->type; 845 if (value < none || value >= cl_max) 846 p = "UNKNOWN"; 847 else 848 p = cam_iosched_control_type_names[value]; 849 850 strlcpy(buf, p, sizeof(buf)); 851 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 852 if (error != 0 || req->newptr == NULL) 853 return error; 854 855 for (i = set_max; i < cl_max; i++) { 856 if (strcmp(buf, cam_iosched_control_type_names[i]) != 0) 857 continue; 858 cam_periph_lock(isc->periph); 859 clp->type = i; 860 cam_periph_unlock(isc->periph); 861 return 0; 862 } 863 864 return EINVAL; 865 } 866 867 static int 868 cam_iosched_sbintime_sysctl(SYSCTL_HANDLER_ARGS) 869 { 870 char buf[16]; 871 sbintime_t value; 872 int error; 873 uint64_t us; 874 875 value = *(sbintime_t *)arg1; 876 us = (uint64_t)value / SBT_1US; 877 snprintf(buf, sizeof(buf), "%ju", (intmax_t)us); 878 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 879 if (error != 0 || req->newptr == NULL) 880 return error; 881 us = strtoul(buf, NULL, 10); 882 if (us == 0) 883 return EINVAL; 884 *(sbintime_t *)arg1 = us * SBT_1US; 885 return 0; 886 } 887 888 static int 889 cam_iosched_sysctl_latencies(SYSCTL_HANDLER_ARGS) 890 { 891 int i, error; 892 struct sbuf sb; 893 uint64_t *latencies; 894 895 latencies = arg1; 896 sbuf_new_for_sysctl(&sb, NULL, LAT_BUCKETS * 16, req); 897 898 for (i = 0; i < LAT_BUCKETS - 1; i++) 899 sbuf_printf(&sb, "%jd,", (intmax_t)latencies[i]); 900 sbuf_printf(&sb, "%jd", (intmax_t)latencies[LAT_BUCKETS - 1]); 901 error = sbuf_finish(&sb); 902 sbuf_delete(&sb); 903 904 return (error); 905 } 906 907 static int 908 cam_iosched_quanta_sysctl(SYSCTL_HANDLER_ARGS) 909 { 910 int *quanta; 911 int error, value; 912 913 quanta = (unsigned *)arg1; 914 value = *quanta; 915 916 error = sysctl_handle_int(oidp, (int *)&value, 0, req); 917 if ((error != 0) || (req->newptr == NULL)) 918 return (error); 919 920 if (value < 1 || value > hz) 921 return (EINVAL); 922 923 *quanta = value; 924 925 return (0); 926 } 927 928 static void 929 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct iop_stats *ios, char *name) 930 { 931 struct sysctl_oid_list *n; 932 struct sysctl_ctx_list *ctx; 933 934 ios->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 935 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, name, 936 CTLFLAG_RD, 0, name); 937 n = SYSCTL_CHILDREN(ios->sysctl_tree); 938 ctx = &ios->sysctl_ctx; 939 940 SYSCTL_ADD_UQUAD(ctx, n, 941 OID_AUTO, "ema", CTLFLAG_RD, 942 &ios->ema, 943 "Fast Exponentially Weighted Moving Average"); 944 SYSCTL_ADD_UQUAD(ctx, n, 945 OID_AUTO, "emvar", CTLFLAG_RD, 946 &ios->emvar, 947 "Fast Exponentially Weighted Moving Variance"); 948 949 SYSCTL_ADD_INT(ctx, n, 950 OID_AUTO, "pending", CTLFLAG_RD, 951 &ios->pending, 0, 952 "Instantaneous # of pending transactions"); 953 SYSCTL_ADD_INT(ctx, n, 954 OID_AUTO, "count", CTLFLAG_RD, 955 &ios->total, 0, 956 "# of transactions submitted to hardware"); 957 SYSCTL_ADD_INT(ctx, n, 958 OID_AUTO, "queued", CTLFLAG_RD, 959 &ios->queued, 0, 960 "# of transactions in the queue"); 961 SYSCTL_ADD_INT(ctx, n, 962 OID_AUTO, "in", CTLFLAG_RD, 963 &ios->in, 0, 964 "# of transactions queued to driver"); 965 SYSCTL_ADD_INT(ctx, n, 966 OID_AUTO, "out", CTLFLAG_RD, 967 &ios->out, 0, 968 "# of transactions completed"); 969 970 SYSCTL_ADD_PROC(ctx, n, 971 OID_AUTO, "limiter", CTLTYPE_STRING | CTLFLAG_RW, 972 ios, 0, cam_iosched_limiter_sysctl, "A", 973 "Current limiting type."); 974 SYSCTL_ADD_INT(ctx, n, 975 OID_AUTO, "min", CTLFLAG_RW, 976 &ios->min, 0, 977 "min resource"); 978 SYSCTL_ADD_INT(ctx, n, 979 OID_AUTO, "max", CTLFLAG_RW, 980 &ios->max, 0, 981 "max resource"); 982 SYSCTL_ADD_INT(ctx, n, 983 OID_AUTO, "current", CTLFLAG_RW, 984 &ios->current, 0, 985 "current resource"); 986 987 SYSCTL_ADD_PROC(ctx, n, 988 OID_AUTO, "latencies", CTLTYPE_STRING | CTLFLAG_RD, 989 &ios->latencies, 0, 990 cam_iosched_sysctl_latencies, "A", 991 "Array of power of 2 latency from 1ms to 1.024s"); 992 } 993 994 static void 995 cam_iosched_iop_stats_fini(struct iop_stats *ios) 996 { 997 if (ios->sysctl_tree) 998 if (sysctl_ctx_free(&ios->sysctl_ctx) != 0) 999 printf("can't remove iosched sysctl stats context\n"); 1000 } 1001 1002 static void 1003 cam_iosched_cl_sysctl_init(struct cam_iosched_softc *isc) 1004 { 1005 struct sysctl_oid_list *n; 1006 struct sysctl_ctx_list *ctx; 1007 struct control_loop *clp; 1008 1009 clp = &isc->cl; 1010 clp->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1011 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, "control", 1012 CTLFLAG_RD, 0, "Control loop info"); 1013 n = SYSCTL_CHILDREN(clp->sysctl_tree); 1014 ctx = &clp->sysctl_ctx; 1015 1016 SYSCTL_ADD_PROC(ctx, n, 1017 OID_AUTO, "type", CTLTYPE_STRING | CTLFLAG_RW, 1018 clp, 0, cam_iosched_control_type_sysctl, "A", 1019 "Control loop algorithm"); 1020 SYSCTL_ADD_PROC(ctx, n, 1021 OID_AUTO, "steer_interval", CTLTYPE_STRING | CTLFLAG_RW, 1022 &clp->steer_interval, 0, cam_iosched_sbintime_sysctl, "A", 1023 "How often to steer (in us)"); 1024 SYSCTL_ADD_PROC(ctx, n, 1025 OID_AUTO, "lolat", CTLTYPE_STRING | CTLFLAG_RW, 1026 &clp->lolat, 0, cam_iosched_sbintime_sysctl, "A", 1027 "Low water mark for Latency (in us)"); 1028 SYSCTL_ADD_PROC(ctx, n, 1029 OID_AUTO, "hilat", CTLTYPE_STRING | CTLFLAG_RW, 1030 &clp->hilat, 0, cam_iosched_sbintime_sysctl, "A", 1031 "Hi water mark for Latency (in us)"); 1032 SYSCTL_ADD_INT(ctx, n, 1033 OID_AUTO, "alpha", CTLFLAG_RW, 1034 &clp->alpha, 0, 1035 "Alpha for PLL (x100) aka gain"); 1036 } 1037 1038 static void 1039 cam_iosched_cl_sysctl_fini(struct control_loop *clp) 1040 { 1041 if (clp->sysctl_tree) 1042 if (sysctl_ctx_free(&clp->sysctl_ctx) != 0) 1043 printf("can't remove iosched sysctl control loop context\n"); 1044 } 1045 #endif 1046 1047 /* 1048 * Allocate the iosched structure. This also insulates callers from knowing 1049 * sizeof struct cam_iosched_softc. 1050 */ 1051 int 1052 cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph) 1053 { 1054 1055 *iscp = malloc(sizeof(**iscp), M_CAMSCHED, M_NOWAIT | M_ZERO); 1056 if (*iscp == NULL) 1057 return ENOMEM; 1058 #ifdef CAM_IOSCHED_DYNAMIC 1059 if (iosched_debug) 1060 printf("CAM IOSCHEDULER Allocating entry at %p\n", *iscp); 1061 #endif 1062 (*iscp)->sort_io_queue = -1; 1063 bioq_init(&(*iscp)->bio_queue); 1064 bioq_init(&(*iscp)->trim_queue); 1065 #ifdef CAM_IOSCHED_DYNAMIC 1066 if (do_dynamic_iosched) { 1067 bioq_init(&(*iscp)->write_queue); 1068 (*iscp)->read_bias = 100; 1069 (*iscp)->current_read_bias = 100; 1070 (*iscp)->quanta = min(hz, 200); 1071 cam_iosched_iop_stats_init(*iscp, &(*iscp)->read_stats); 1072 cam_iosched_iop_stats_init(*iscp, &(*iscp)->write_stats); 1073 cam_iosched_iop_stats_init(*iscp, &(*iscp)->trim_stats); 1074 (*iscp)->trim_stats.max = 1; /* Trims are special: one at a time for now */ 1075 (*iscp)->last_time = sbinuptime(); 1076 callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0); 1077 (*iscp)->periph = periph; 1078 cam_iosched_cl_init(&(*iscp)->cl, *iscp); 1079 callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta, cam_iosched_ticker, *iscp); 1080 (*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1081 } 1082 #endif 1083 1084 return 0; 1085 } 1086 1087 /* 1088 * Reclaim all used resources. This assumes that other folks have 1089 * drained the requests in the hardware. Maybe an unwise assumption. 1090 */ 1091 void 1092 cam_iosched_fini(struct cam_iosched_softc *isc) 1093 { 1094 if (isc) { 1095 cam_iosched_flush(isc, NULL, ENXIO); 1096 #ifdef CAM_IOSCHED_DYNAMIC 1097 cam_iosched_iop_stats_fini(&isc->read_stats); 1098 cam_iosched_iop_stats_fini(&isc->write_stats); 1099 cam_iosched_iop_stats_fini(&isc->trim_stats); 1100 cam_iosched_cl_sysctl_fini(&isc->cl); 1101 if (isc->sysctl_tree) 1102 if (sysctl_ctx_free(&isc->sysctl_ctx) != 0) 1103 printf("can't remove iosched sysctl stats context\n"); 1104 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) { 1105 callout_drain(&isc->ticker); 1106 isc->flags &= ~ CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1107 } 1108 #endif 1109 free(isc, M_CAMSCHED); 1110 } 1111 } 1112 1113 /* 1114 * After we're sure we're attaching a device, go ahead and add 1115 * hooks for any sysctl we may wish to honor. 1116 */ 1117 void cam_iosched_sysctl_init(struct cam_iosched_softc *isc, 1118 struct sysctl_ctx_list *ctx, struct sysctl_oid *node) 1119 { 1120 #ifdef CAM_IOSCHED_DYNAMIC 1121 struct sysctl_oid_list *n; 1122 #endif 1123 1124 SYSCTL_ADD_INT(ctx, SYSCTL_CHILDREN(node), 1125 OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE, 1126 &isc->sort_io_queue, 0, 1127 "Sort IO queue to try and optimise disk access patterns"); 1128 1129 #ifdef CAM_IOSCHED_DYNAMIC 1130 if (!do_dynamic_iosched) 1131 return; 1132 1133 isc->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1134 SYSCTL_CHILDREN(node), OID_AUTO, "iosched", 1135 CTLFLAG_RD, 0, "I/O scheduler statistics"); 1136 n = SYSCTL_CHILDREN(isc->sysctl_tree); 1137 ctx = &isc->sysctl_ctx; 1138 1139 cam_iosched_iop_stats_sysctl_init(isc, &isc->read_stats, "read"); 1140 cam_iosched_iop_stats_sysctl_init(isc, &isc->write_stats, "write"); 1141 cam_iosched_iop_stats_sysctl_init(isc, &isc->trim_stats, "trim"); 1142 cam_iosched_cl_sysctl_init(isc); 1143 1144 SYSCTL_ADD_INT(ctx, n, 1145 OID_AUTO, "read_bias", CTLFLAG_RW, 1146 &isc->read_bias, 100, 1147 "How biased towards read should we be independent of limits"); 1148 1149 SYSCTL_ADD_PROC(ctx, n, 1150 OID_AUTO, "quanta", CTLTYPE_UINT | CTLFLAG_RW, 1151 &isc->quanta, 0, cam_iosched_quanta_sysctl, "I", 1152 "How many quanta per second do we slice the I/O up into"); 1153 1154 SYSCTL_ADD_INT(ctx, n, 1155 OID_AUTO, "total_ticks", CTLFLAG_RD, 1156 &isc->total_ticks, 0, 1157 "Total number of ticks we've done"); 1158 1159 SYSCTL_ADD_INT(ctx, n, 1160 OID_AUTO, "load", CTLFLAG_RD, 1161 &isc->load, 0, 1162 "scaled load average / 100"); 1163 #endif 1164 } 1165 1166 /* 1167 * Flush outstanding I/O. Consumers of this library don't know all the 1168 * queues we may keep, so this allows all I/O to be flushed in one 1169 * convenient call. 1170 */ 1171 void 1172 cam_iosched_flush(struct cam_iosched_softc *isc, struct devstat *stp, int err) 1173 { 1174 bioq_flush(&isc->bio_queue, stp, err); 1175 bioq_flush(&isc->trim_queue, stp, err); 1176 #ifdef CAM_IOSCHED_DYNAMIC 1177 if (do_dynamic_iosched) 1178 bioq_flush(&isc->write_queue, stp, err); 1179 #endif 1180 } 1181 1182 #ifdef CAM_IOSCHED_DYNAMIC 1183 static struct bio * 1184 cam_iosched_get_write(struct cam_iosched_softc *isc) 1185 { 1186 struct bio *bp; 1187 1188 /* 1189 * We control the write rate by controlling how many requests we send 1190 * down to the drive at any one time. Fewer requests limits the 1191 * effects of both starvation when the requests take a while and write 1192 * amplification when each request is causing more than one write to 1193 * the NAND media. Limiting the queue depth like this will also limit 1194 * the write throughput and give and reads that want to compete to 1195 * compete unfairly. 1196 */ 1197 bp = bioq_first(&isc->write_queue); 1198 if (bp == NULL) { 1199 if (iosched_debug > 3) 1200 printf("No writes present in write_queue\n"); 1201 return NULL; 1202 } 1203 1204 /* 1205 * If pending read, prefer that based on current read bias 1206 * setting. 1207 */ 1208 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) { 1209 if (iosched_debug) 1210 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); 1211 isc->current_read_bias--; 1212 /* We're not limiting writes, per se, just doing reads first */ 1213 return NULL; 1214 } 1215 1216 /* 1217 * See if our current limiter allows this I/O. 1218 */ 1219 if (cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) { 1220 if (iosched_debug) 1221 printf("Can't write because limiter says no.\n"); 1222 isc->write_stats.state_flags |= IOP_RATE_LIMITED; 1223 return NULL; 1224 } 1225 1226 /* 1227 * Let's do this: We've passed all the gates and we're a go 1228 * to schedule the I/O in the SIM. 1229 */ 1230 isc->current_read_bias = isc->read_bias; 1231 bioq_remove(&isc->write_queue, bp); 1232 if (bp->bio_cmd == BIO_WRITE) { 1233 isc->write_stats.queued--; 1234 isc->write_stats.total++; 1235 isc->write_stats.pending++; 1236 } 1237 if (iosched_debug > 9) 1238 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1239 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED; 1240 return bp; 1241 } 1242 #endif 1243 1244 /* 1245 * Put back a trim that you weren't able to actually schedule this time. 1246 */ 1247 void 1248 cam_iosched_put_back_trim(struct cam_iosched_softc *isc, struct bio *bp) 1249 { 1250 bioq_insert_head(&isc->trim_queue, bp); 1251 #ifdef CAM_IOSCHED_DYNAMIC 1252 isc->trim_stats.queued++; 1253 isc->trim_stats.total--; /* since we put it back, don't double count */ 1254 isc->trim_stats.pending--; 1255 #endif 1256 } 1257 1258 /* 1259 * gets the next trim from the trim queue. 1260 * 1261 * Assumes we're called with the periph lock held. It removes this 1262 * trim from the queue and the device must explicitly reinsert it 1263 * should the need arise. 1264 */ 1265 struct bio * 1266 cam_iosched_next_trim(struct cam_iosched_softc *isc) 1267 { 1268 struct bio *bp; 1269 1270 bp = bioq_first(&isc->trim_queue); 1271 if (bp == NULL) 1272 return NULL; 1273 bioq_remove(&isc->trim_queue, bp); 1274 #ifdef CAM_IOSCHED_DYNAMIC 1275 isc->trim_stats.queued--; 1276 isc->trim_stats.total++; 1277 isc->trim_stats.pending++; 1278 #endif 1279 return bp; 1280 } 1281 1282 /* 1283 * gets an available trim from the trim queue, if there's no trim 1284 * already pending. It removes this trim from the queue and the device 1285 * must explicitly reinsert it should the need arise. 1286 * 1287 * Assumes we're called with the periph lock held. 1288 */ 1289 struct bio * 1290 cam_iosched_get_trim(struct cam_iosched_softc *isc) 1291 { 1292 1293 if (!cam_iosched_has_more_trim(isc)) 1294 return NULL; 1295 1296 return cam_iosched_next_trim(isc); 1297 } 1298 1299 /* 1300 * Determine what the next bit of work to do is for the periph. The 1301 * default implementation looks to see if we have trims to do, but no 1302 * trims outstanding. If so, we do that. Otherwise we see if we have 1303 * other work. If we do, then we do that. Otherwise why were we called? 1304 */ 1305 struct bio * 1306 cam_iosched_next_bio(struct cam_iosched_softc *isc) 1307 { 1308 struct bio *bp; 1309 1310 /* 1311 * See if we have a trim that can be scheduled. We can only send one 1312 * at a time down, so this takes that into account. 1313 * 1314 * XXX newer TRIM commands are queueable. Revisit this when we 1315 * implement them. 1316 */ 1317 if ((bp = cam_iosched_get_trim(isc)) != NULL) 1318 return bp; 1319 1320 #ifdef CAM_IOSCHED_DYNAMIC 1321 /* 1322 * See if we have any pending writes, and room in the queue for them, 1323 * and if so, those are next. 1324 */ 1325 if (do_dynamic_iosched) { 1326 if ((bp = cam_iosched_get_write(isc)) != NULL) 1327 return bp; 1328 } 1329 #endif 1330 1331 /* 1332 * next, see if there's other, normal I/O waiting. If so return that. 1333 */ 1334 if ((bp = bioq_first(&isc->bio_queue)) == NULL) 1335 return NULL; 1336 1337 #ifdef CAM_IOSCHED_DYNAMIC 1338 /* 1339 * For the dynamic scheduler, bio_queue is only for reads, so enforce 1340 * the limits here. Enforce only for reads. 1341 */ 1342 if (do_dynamic_iosched) { 1343 if (bp->bio_cmd == BIO_READ && 1344 cam_iosched_limiter_iop(&isc->read_stats, bp) != 0) { 1345 isc->read_stats.state_flags |= IOP_RATE_LIMITED; 1346 return NULL; 1347 } 1348 } 1349 isc->read_stats.state_flags &= ~IOP_RATE_LIMITED; 1350 #endif 1351 bioq_remove(&isc->bio_queue, bp); 1352 #ifdef CAM_IOSCHED_DYNAMIC 1353 if (do_dynamic_iosched) { 1354 if (bp->bio_cmd == BIO_READ) { 1355 isc->read_stats.queued--; 1356 isc->read_stats.total++; 1357 isc->read_stats.pending++; 1358 } else 1359 printf("Found bio_cmd = %#x\n", bp->bio_cmd); 1360 } 1361 if (iosched_debug > 9) 1362 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1363 #endif 1364 return bp; 1365 } 1366 1367 /* 1368 * Driver has been given some work to do by the block layer. Tell the 1369 * scheduler about it and have it queue the work up. The scheduler module 1370 * will then return the currently most useful bit of work later, possibly 1371 * deferring work for various reasons. 1372 */ 1373 void 1374 cam_iosched_queue_work(struct cam_iosched_softc *isc, struct bio *bp) 1375 { 1376 1377 /* 1378 * Put all trims on the trim queue sorted, since we know 1379 * that the collapsing code requires this. Otherwise put 1380 * the work on the bio queue. 1381 */ 1382 if (bp->bio_cmd == BIO_DELETE) { 1383 bioq_disksort(&isc->trim_queue, bp); 1384 #ifdef CAM_IOSCHED_DYNAMIC 1385 isc->trim_stats.in++; 1386 isc->trim_stats.queued++; 1387 #endif 1388 } 1389 #ifdef CAM_IOSCHED_DYNAMIC 1390 else if (do_dynamic_iosched && (bp->bio_cmd != BIO_READ)) { 1391 if (cam_iosched_sort_queue(isc)) 1392 bioq_disksort(&isc->write_queue, bp); 1393 else 1394 bioq_insert_tail(&isc->write_queue, bp); 1395 if (iosched_debug > 9) 1396 printf("Qw : %p %#x\n", bp, bp->bio_cmd); 1397 if (bp->bio_cmd == BIO_WRITE) { 1398 isc->write_stats.in++; 1399 isc->write_stats.queued++; 1400 } 1401 } 1402 #endif 1403 else { 1404 if (cam_iosched_sort_queue(isc)) 1405 bioq_disksort(&isc->bio_queue, bp); 1406 else 1407 bioq_insert_tail(&isc->bio_queue, bp); 1408 #ifdef CAM_IOSCHED_DYNAMIC 1409 if (iosched_debug > 9) 1410 printf("Qr : %p %#x\n", bp, bp->bio_cmd); 1411 if (bp->bio_cmd == BIO_READ) { 1412 isc->read_stats.in++; 1413 isc->read_stats.queued++; 1414 } else if (bp->bio_cmd == BIO_WRITE) { 1415 isc->write_stats.in++; 1416 isc->write_stats.queued++; 1417 } 1418 #endif 1419 } 1420 } 1421 1422 /* 1423 * If we have work, get it scheduled. Called with the periph lock held. 1424 */ 1425 void 1426 cam_iosched_schedule(struct cam_iosched_softc *isc, struct cam_periph *periph) 1427 { 1428 1429 if (cam_iosched_has_work(isc)) 1430 xpt_schedule(periph, CAM_PRIORITY_NORMAL); 1431 } 1432 1433 /* 1434 * Complete a trim request. Mark that we no longer have one in flight. 1435 */ 1436 void 1437 cam_iosched_trim_done(struct cam_iosched_softc *isc) 1438 { 1439 1440 isc->flags &= ~CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1441 } 1442 1443 /* 1444 * Complete a bio. Called before we release the ccb with xpt_release_ccb so we 1445 * might use notes in the ccb for statistics. 1446 */ 1447 int 1448 cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp, 1449 union ccb *done_ccb) 1450 { 1451 int retval = 0; 1452 #ifdef CAM_IOSCHED_DYNAMIC 1453 if (!do_dynamic_iosched) 1454 return retval; 1455 1456 if (iosched_debug > 10) 1457 printf("done: %p %#x\n", bp, bp->bio_cmd); 1458 if (bp->bio_cmd == BIO_WRITE) { 1459 retval = cam_iosched_limiter_iodone(&isc->write_stats, bp); 1460 isc->write_stats.out++; 1461 isc->write_stats.pending--; 1462 } else if (bp->bio_cmd == BIO_READ) { 1463 retval = cam_iosched_limiter_iodone(&isc->read_stats, bp); 1464 isc->read_stats.out++; 1465 isc->read_stats.pending--; 1466 } else if (bp->bio_cmd == BIO_DELETE) { 1467 isc->trim_stats.out++; 1468 isc->trim_stats.pending--; 1469 } else if (bp->bio_cmd != BIO_FLUSH) { 1470 if (iosched_debug) 1471 printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd); 1472 } 1473 1474 if (!(bp->bio_flags & BIO_ERROR)) 1475 cam_iosched_io_metric_update(isc, 1476 cam_iosched_sbintime_t(done_ccb->ccb_h.qos.periph_data), 1477 bp->bio_cmd, bp->bio_bcount); 1478 #endif 1479 return retval; 1480 } 1481 1482 /* 1483 * Tell the io scheduler that you've pushed a trim down into the sim. 1484 * This also tells the I/O scheduler not to push any more trims down, so 1485 * some periphs do not call it if they can cope with multiple trims in flight. 1486 */ 1487 void 1488 cam_iosched_submit_trim(struct cam_iosched_softc *isc) 1489 { 1490 1491 isc->flags |= CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1492 } 1493 1494 /* 1495 * Change the sorting policy hint for I/O transactions for this device. 1496 */ 1497 void 1498 cam_iosched_set_sort_queue(struct cam_iosched_softc *isc, int val) 1499 { 1500 1501 isc->sort_io_queue = val; 1502 } 1503 1504 int 1505 cam_iosched_has_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1506 { 1507 return isc->flags & flags; 1508 } 1509 1510 void 1511 cam_iosched_set_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1512 { 1513 isc->flags |= flags; 1514 } 1515 1516 void 1517 cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1518 { 1519 isc->flags &= ~flags; 1520 } 1521 1522 #ifdef CAM_IOSCHED_DYNAMIC 1523 /* 1524 * After the method presented in Jack Crenshaw's 1998 article "Integer 1525 * Square Roots," reprinted at 1526 * http://www.embedded.com/electronics-blogs/programmer-s-toolbox/4219659/Integer-Square-Roots 1527 * and well worth the read. Briefly, we find the power of 4 that's the 1528 * largest smaller than val. We then check each smaller power of 4 to 1529 * see if val is still bigger. The right shifts at each step divide 1530 * the result by 2 which after successive application winds up 1531 * accumulating the right answer. It could also have been accumulated 1532 * using a separate root counter, but this code is smaller and faster 1533 * than that method. This method is also integer size invariant. 1534 * It returns floor(sqrt((float)val)), or the largest integer less than 1535 * or equal to the square root. 1536 */ 1537 static uint64_t 1538 isqrt64(uint64_t val) 1539 { 1540 uint64_t res = 0; 1541 uint64_t bit = 1ULL << (sizeof(uint64_t) * NBBY - 2); 1542 1543 /* 1544 * Find the largest power of 4 smaller than val. 1545 */ 1546 while (bit > val) 1547 bit >>= 2; 1548 1549 /* 1550 * Accumulate the answer, one bit at a time (we keep moving 1551 * them over since 2 is the square root of 4 and we test 1552 * powers of 4). We accumulate where we find the bit, but 1553 * the successive shifts land the bit in the right place 1554 * by the end. 1555 */ 1556 while (bit != 0) { 1557 if (val >= res + bit) { 1558 val -= res + bit; 1559 res = (res >> 1) + bit; 1560 } else 1561 res >>= 1; 1562 bit >>= 2; 1563 } 1564 1565 return res; 1566 } 1567 1568 static sbintime_t latencies[LAT_BUCKETS - 1] = { 1569 SBT_1MS << 0, 1570 SBT_1MS << 1, 1571 SBT_1MS << 2, 1572 SBT_1MS << 3, 1573 SBT_1MS << 4, 1574 SBT_1MS << 5, 1575 SBT_1MS << 6, 1576 SBT_1MS << 7, 1577 SBT_1MS << 8, 1578 SBT_1MS << 9, 1579 SBT_1MS << 10, 1580 SBT_1MS << 11, 1581 SBT_1MS << 12, 1582 SBT_1MS << 13 /* 8.192s */ 1583 }; 1584 1585 static void 1586 cam_iosched_update(struct iop_stats *iop, sbintime_t sim_latency) 1587 { 1588 sbintime_t y, deltasq, delta; 1589 int i; 1590 1591 /* 1592 * Keep counts for latency. We do it by power of two buckets. 1593 * This helps us spot outlier behavior obscured by averages. 1594 */ 1595 for (i = 0; i < LAT_BUCKETS - 1; i++) { 1596 if (sim_latency < latencies[i]) { 1597 iop->latencies[i]++; 1598 break; 1599 } 1600 } 1601 if (i == LAT_BUCKETS - 1) 1602 iop->latencies[i]++; /* Put all > 1024ms values into the last bucket. */ 1603 1604 /* 1605 * Classic exponentially decaying average with a tiny alpha 1606 * (2 ^ -alpha_bits). For more info see the NIST statistical 1607 * handbook. 1608 * 1609 * ema_t = y_t * alpha + ema_t-1 * (1 - alpha) [nist] 1610 * ema_t = y_t * alpha + ema_t-1 - alpha * ema_t-1 1611 * ema_t = alpha * y_t - alpha * ema_t-1 + ema_t-1 1612 * alpha = 1 / (1 << alpha_bits) 1613 * sub e == ema_t-1, b == 1/alpha (== 1 << alpha_bits), d == y_t - ema_t-1 1614 * = y_t/b - e/b + be/b 1615 * = (y_t - e + be) / b 1616 * = (e + d) / b 1617 * 1618 * Since alpha is a power of two, we can compute this w/o any mult or 1619 * division. 1620 * 1621 * Variance can also be computed. Usually, it would be expressed as follows: 1622 * diff_t = y_t - ema_t-1 1623 * emvar_t = (1 - alpha) * (emavar_t-1 + diff_t^2 * alpha) 1624 * = emavar_t-1 - alpha * emavar_t-1 + delta_t^2 * alpha - (delta_t * alpha)^2 1625 * sub b == 1/alpha (== 1 << alpha_bits), e == emavar_t-1, d = delta_t^2 1626 * = e - e/b + dd/b + dd/bb 1627 * = (bbe - be + bdd + dd) / bb 1628 * = (bbe + b(dd-e) + dd) / bb (which is expanded below bb = 1<<(2*alpha_bits)) 1629 */ 1630 /* 1631 * XXX possible numeric issues 1632 * o We assume right shifted integers do the right thing, since that's 1633 * implementation defined. You can change the right shifts to / (1LL << alpha). 1634 * o alpha_bits = 9 gives ema ceiling of 23 bits of seconds for ema and 14 bits 1635 * for emvar. This puts a ceiling of 13 bits on alpha since we need a 1636 * few tens of seconds of representation. 1637 * o We mitigate alpha issues by never setting it too high. 1638 */ 1639 y = sim_latency; 1640 delta = (y - iop->ema); /* d */ 1641 iop->ema = ((iop->ema << alpha_bits) + delta) >> alpha_bits; 1642 1643 /* 1644 * Were we to naively plow ahead at this point, we wind up with many numerical 1645 * issues making any SD > ~3ms unreliable. So, we shift right by 12. This leaves 1646 * us with microsecond level precision in the input, so the same in the 1647 * output. It means we can't overflow deltasq unless delta > 4k seconds. It 1648 * also means that emvar can be up 46 bits 40 of which are fraction, which 1649 * gives us a way to measure up to ~8s in the SD before the computation goes 1650 * unstable. Even the worst hard disk rarely has > 1s service time in the 1651 * drive. It does mean we have to shift left 12 bits after taking the 1652 * square root to compute the actual standard deviation estimate. This loss of 1653 * precision is preferable to needing int128 types to work. The above numbers 1654 * assume alpha=9. 10 or 11 are ok, but we start to run into issues at 12, 1655 * so 12 or 13 is OK for EMA, EMVAR and SD will be wrong in those cases. 1656 */ 1657 delta >>= 12; 1658 deltasq = delta * delta; /* dd */ 1659 iop->emvar = ((iop->emvar << (2 * alpha_bits)) + /* bbe */ 1660 ((deltasq - iop->emvar) << alpha_bits) + /* b(dd-e) */ 1661 deltasq) /* dd */ 1662 >> (2 * alpha_bits); /* div bb */ 1663 iop->sd = (sbintime_t)isqrt64((uint64_t)iop->emvar) << 12; 1664 } 1665 1666 static void 1667 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 1668 sbintime_t sim_latency, int cmd, size_t size) 1669 { 1670 /* xxx Do we need to scale based on the size of the I/O ? */ 1671 switch (cmd) { 1672 case BIO_READ: 1673 cam_iosched_update(&isc->read_stats, sim_latency); 1674 break; 1675 case BIO_WRITE: 1676 cam_iosched_update(&isc->write_stats, sim_latency); 1677 break; 1678 case BIO_DELETE: 1679 cam_iosched_update(&isc->trim_stats, sim_latency); 1680 break; 1681 default: 1682 break; 1683 } 1684 } 1685 1686 #ifdef DDB 1687 static int biolen(struct bio_queue_head *bq) 1688 { 1689 int i = 0; 1690 struct bio *bp; 1691 1692 TAILQ_FOREACH(bp, &bq->queue, bio_queue) { 1693 i++; 1694 } 1695 return i; 1696 } 1697 1698 /* 1699 * Show the internal state of the I/O scheduler. 1700 */ 1701 DB_SHOW_COMMAND(iosched, cam_iosched_db_show) 1702 { 1703 struct cam_iosched_softc *isc; 1704 1705 if (!have_addr) { 1706 db_printf("Need addr\n"); 1707 return; 1708 } 1709 isc = (struct cam_iosched_softc *)addr; 1710 db_printf("pending_reads: %d\n", isc->read_stats.pending); 1711 db_printf("min_reads: %d\n", isc->read_stats.min); 1712 db_printf("max_reads: %d\n", isc->read_stats.max); 1713 db_printf("reads: %d\n", isc->read_stats.total); 1714 db_printf("in_reads: %d\n", isc->read_stats.in); 1715 db_printf("out_reads: %d\n", isc->read_stats.out); 1716 db_printf("queued_reads: %d\n", isc->read_stats.queued); 1717 db_printf("Current Q len %d\n", biolen(&isc->bio_queue)); 1718 db_printf("pending_writes: %d\n", isc->write_stats.pending); 1719 db_printf("min_writes: %d\n", isc->write_stats.min); 1720 db_printf("max_writes: %d\n", isc->write_stats.max); 1721 db_printf("writes: %d\n", isc->write_stats.total); 1722 db_printf("in_writes: %d\n", isc->write_stats.in); 1723 db_printf("out_writes: %d\n", isc->write_stats.out); 1724 db_printf("queued_writes: %d\n", isc->write_stats.queued); 1725 db_printf("Current Q len %d\n", biolen(&isc->write_queue)); 1726 db_printf("pending_trims: %d\n", isc->trim_stats.pending); 1727 db_printf("min_trims: %d\n", isc->trim_stats.min); 1728 db_printf("max_trims: %d\n", isc->trim_stats.max); 1729 db_printf("trims: %d\n", isc->trim_stats.total); 1730 db_printf("in_trims: %d\n", isc->trim_stats.in); 1731 db_printf("out_trims: %d\n", isc->trim_stats.out); 1732 db_printf("queued_trims: %d\n", isc->trim_stats.queued); 1733 db_printf("Current Q len %d\n", biolen(&isc->trim_queue)); 1734 db_printf("read_bias: %d\n", isc->read_bias); 1735 db_printf("current_read_bias: %d\n", isc->current_read_bias); 1736 db_printf("Trim active? %s\n", 1737 (isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) ? "yes" : "no"); 1738 } 1739 #endif 1740 #endif 1741