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. If current iops is 0, treat that 461 * as unlimited as a failsafe. 462 */ 463 if (ios->current > 0 && ios->l_value1 <= 0) 464 return EAGAIN; 465 return 0; 466 } 467 468 static int 469 cam_iosched_iops_iop(struct iop_stats *ios, struct bio *bp) 470 { 471 int rv; 472 473 rv = cam_iosched_limiter_caniop(ios, bp); 474 if (rv == 0) 475 ios->l_value1--; 476 477 return rv; 478 } 479 480 static int 481 cam_iosched_bw_init(struct iop_stats *ios) 482 { 483 484 /* ios->current is in kB/s, so scale to bytes */ 485 ios->l_value1 = ios->current * 1000 / ios->softc->quanta; 486 487 return 0; 488 } 489 490 static int 491 cam_iosched_bw_tick(struct iop_stats *ios) 492 { 493 int bw; 494 495 /* 496 * If we're in the hole for available quota from 497 * the last time, then add the quantum for this. 498 * If we have any left over from last quantum, 499 * then too bad, that's lost. Also, ios->current 500 * is in kB/s, so scale. 501 * 502 * We also allow up to 4 quanta of credits to 503 * accumulate to deal with burstiness. 4 is extremely 504 * arbitrary. 505 */ 506 bw = (int)((ios->current * 1000ull * (uint64_t)ios->softc->this_frac) >> 16); 507 if (ios->l_value1 < bw * 4) 508 ios->l_value1 += bw; 509 510 return 0; 511 } 512 513 static int 514 cam_iosched_bw_caniop(struct iop_stats *ios, struct bio *bp) 515 { 516 /* 517 * So if we have any more bw quota left, allow it, 518 * otherwise wait. Note, we'll go negative and that's 519 * OK. We'll just get a little less next quota. 520 * 521 * Note on going negative: that allows us to process 522 * requests in order better, since we won't allow 523 * shorter reads to get around the long one that we 524 * don't have the quota to do just yet. It also prevents 525 * starvation by being a little more permissive about 526 * what we let through this quantum (to prevent the 527 * starvation), at the cost of getting a little less 528 * next quantum. 529 * 530 * Also note that if the current limit is <= 0, 531 * we treat it as unlimited as a failsafe. 532 */ 533 if (ios->current > 0 && ios->l_value1 <= 0) 534 return EAGAIN; 535 536 537 return 0; 538 } 539 540 static int 541 cam_iosched_bw_iop(struct iop_stats *ios, struct bio *bp) 542 { 543 int rv; 544 545 rv = cam_iosched_limiter_caniop(ios, bp); 546 if (rv == 0) 547 ios->l_value1 -= bp->bio_length; 548 549 return rv; 550 } 551 552 static void cam_iosched_cl_maybe_steer(struct control_loop *clp); 553 554 static void 555 cam_iosched_ticker(void *arg) 556 { 557 struct cam_iosched_softc *isc = arg; 558 sbintime_t now, delta; 559 int pending; 560 561 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc); 562 563 now = sbinuptime(); 564 delta = now - isc->last_time; 565 isc->this_frac = (uint32_t)delta >> 16; /* Note: discards seconds -- should be 0 harmless if not */ 566 isc->last_time = now; 567 568 cam_iosched_cl_maybe_steer(&isc->cl); 569 570 cam_iosched_limiter_tick(&isc->read_stats); 571 cam_iosched_limiter_tick(&isc->write_stats); 572 cam_iosched_limiter_tick(&isc->trim_stats); 573 574 cam_iosched_schedule(isc, isc->periph); 575 576 /* 577 * isc->load is an EMA of the pending I/Os at each tick. The number of 578 * pending I/Os is the sum of the I/Os queued to the hardware, and those 579 * in the software queue that could be queued to the hardware if there 580 * were slots. 581 * 582 * ios_stats.pending is a count of requests in the SIM right now for 583 * each of these types of I/O. So the total pending count is the sum of 584 * these I/Os and the sum of the queued I/Os still in the software queue 585 * for those operations that aren't being rate limited at the moment. 586 * 587 * The reason for the rate limiting bit is because those I/Os 588 * aren't part of the software queued load (since we could 589 * give them to hardware, but choose not to). 590 * 591 * Note: due to a bug in counting pending TRIM in the device, we 592 * don't include them in this count. We count each BIO_DELETE in 593 * the pending count, but the periph drivers collapse them down 594 * into one TRIM command. That one trim command gets the completion 595 * so the counts get off. 596 */ 597 pending = isc->read_stats.pending + isc->write_stats.pending /* + isc->trim_stats.pending */; 598 pending += !!(isc->read_stats.state_flags & IOP_RATE_LIMITED) * isc->read_stats.queued + 599 !!(isc->write_stats.state_flags & IOP_RATE_LIMITED) * isc->write_stats.queued /* + 600 !!(isc->trim_stats.state_flags & IOP_RATE_LIMITED) * isc->trim_stats.queued */ ; 601 pending <<= 16; 602 pending /= isc->periph->path->device->ccbq.total_openings; 603 604 isc->load = (pending + (isc->load << 13) - isc->load) >> 13; /* see above: 13 -> 16139 / 200/s = ~81s ~1 minute */ 605 606 isc->total_ticks++; 607 } 608 609 610 static void 611 cam_iosched_cl_init(struct control_loop *clp, struct cam_iosched_softc *isc) 612 { 613 614 clp->next_steer = sbinuptime(); 615 clp->softc = isc; 616 clp->steer_interval = SBT_1S * 5; /* Let's start out steering every 5s */ 617 clp->lolat = 5 * SBT_1MS; 618 clp->hilat = 15 * SBT_1MS; 619 clp->alpha = 20; /* Alpha == gain. 20 = .2 */ 620 clp->type = set_max; 621 } 622 623 static void 624 cam_iosched_cl_maybe_steer(struct control_loop *clp) 625 { 626 struct cam_iosched_softc *isc; 627 sbintime_t now, lat; 628 int old; 629 630 isc = clp->softc; 631 now = isc->last_time; 632 if (now < clp->next_steer) 633 return; 634 635 clp->next_steer = now + clp->steer_interval; 636 switch (clp->type) { 637 case set_max: 638 if (isc->write_stats.current != isc->write_stats.max) 639 printf("Steering write from %d kBps to %d kBps\n", 640 isc->write_stats.current, isc->write_stats.max); 641 isc->read_stats.current = isc->read_stats.max; 642 isc->write_stats.current = isc->write_stats.max; 643 isc->trim_stats.current = isc->trim_stats.max; 644 break; 645 case read_latency: 646 old = isc->write_stats.current; 647 lat = isc->read_stats.ema; 648 /* 649 * Simple PLL-like engine. Since we're steering to a range for 650 * the SP (set point) that makes things a little more 651 * complicated. In addition, we're not directly controlling our 652 * PV (process variable), the read latency, but instead are 653 * manipulating the write bandwidth limit for our MV 654 * (manipulation variable), analysis of this code gets a bit 655 * messy. Also, the MV is a very noisy control surface for read 656 * latency since it is affected by many hidden processes inside 657 * the device which change how responsive read latency will be 658 * in reaction to changes in write bandwidth. Unlike the classic 659 * boiler control PLL. this may result in over-steering while 660 * the SSD takes its time to react to the new, lower load. This 661 * is why we use a relatively low alpha of between .1 and .25 to 662 * compensate for this effect. At .1, it takes ~22 steering 663 * intervals to back off by a factor of 10. At .2 it only takes 664 * ~10. At .25 it only takes ~8. However some preliminary data 665 * from the SSD drives suggests a reasponse time in 10's of 666 * seconds before latency drops regardless of the new write 667 * rate. Careful observation will be required to tune this 668 * effectively. 669 * 670 * Also, when there's no read traffic, we jack up the write 671 * limit too regardless of the last read latency. 10 is 672 * somewhat arbitrary. 673 */ 674 if (lat < clp->lolat || isc->read_stats.total - clp->last_count < 10) 675 isc->write_stats.current = isc->write_stats.current * 676 (100 + clp->alpha) / 100; /* Scale up */ 677 else if (lat > clp->hilat) 678 isc->write_stats.current = isc->write_stats.current * 679 (100 - clp->alpha) / 100; /* Scale down */ 680 clp->last_count = isc->read_stats.total; 681 682 /* 683 * Even if we don't steer, per se, enforce the min/max limits as 684 * those may have changed. 685 */ 686 if (isc->write_stats.current < isc->write_stats.min) 687 isc->write_stats.current = isc->write_stats.min; 688 if (isc->write_stats.current > isc->write_stats.max) 689 isc->write_stats.current = isc->write_stats.max; 690 if (old != isc->write_stats.current && iosched_debug) 691 printf("Steering write from %d kBps to %d kBps due to latency of %jdus\n", 692 old, isc->write_stats.current, 693 (uintmax_t)((uint64_t)1000000 * (uint32_t)lat) >> 32); 694 break; 695 case cl_max: 696 break; 697 } 698 } 699 #endif 700 701 /* 702 * Trim or similar currently pending completion. Should only be set for 703 * those drivers wishing only one Trim active at a time. 704 */ 705 #define CAM_IOSCHED_FLAG_TRIM_ACTIVE (1ul << 0) 706 /* Callout active, and needs to be torn down */ 707 #define CAM_IOSCHED_FLAG_CALLOUT_ACTIVE (1ul << 1) 708 709 /* Periph drivers set these flags to indicate work */ 710 #define CAM_IOSCHED_FLAG_WORK_FLAGS ((0xffffu) << 16) 711 712 #ifdef CAM_IOSCHED_DYNAMIC 713 static void 714 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 715 sbintime_t sim_latency, int cmd, size_t size); 716 #endif 717 718 static inline int 719 cam_iosched_has_flagged_work(struct cam_iosched_softc *isc) 720 { 721 return !!(isc->flags & CAM_IOSCHED_FLAG_WORK_FLAGS); 722 } 723 724 static inline int 725 cam_iosched_has_io(struct cam_iosched_softc *isc) 726 { 727 #ifdef CAM_IOSCHED_DYNAMIC 728 if (do_dynamic_iosched) { 729 struct bio *rbp = bioq_first(&isc->bio_queue); 730 struct bio *wbp = bioq_first(&isc->write_queue); 731 int can_write = wbp != NULL && 732 cam_iosched_limiter_caniop(&isc->write_stats, wbp) == 0; 733 int can_read = rbp != NULL && 734 cam_iosched_limiter_caniop(&isc->read_stats, rbp) == 0; 735 if (iosched_debug > 2) { 736 printf("can write %d: pending_writes %d max_writes %d\n", can_write, isc->write_stats.pending, isc->write_stats.max); 737 printf("can read %d: read_stats.pending %d max_reads %d\n", can_read, isc->read_stats.pending, isc->read_stats.max); 738 printf("Queued reads %d writes %d\n", isc->read_stats.queued, isc->write_stats.queued); 739 } 740 return can_read || can_write; 741 } 742 #endif 743 return bioq_first(&isc->bio_queue) != NULL; 744 } 745 746 static inline int 747 cam_iosched_has_more_trim(struct cam_iosched_softc *isc) 748 { 749 return !(isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) && 750 bioq_first(&isc->trim_queue); 751 } 752 753 #define cam_iosched_sort_queue(isc) ((isc)->sort_io_queue >= 0 ? \ 754 (isc)->sort_io_queue : cam_sort_io_queues) 755 756 757 static inline int 758 cam_iosched_has_work(struct cam_iosched_softc *isc) 759 { 760 #ifdef CAM_IOSCHED_DYNAMIC 761 if (iosched_debug > 2) 762 printf("has work: %d %d %d\n", cam_iosched_has_io(isc), 763 cam_iosched_has_more_trim(isc), 764 cam_iosched_has_flagged_work(isc)); 765 #endif 766 767 return cam_iosched_has_io(isc) || 768 cam_iosched_has_more_trim(isc) || 769 cam_iosched_has_flagged_work(isc); 770 } 771 772 #ifdef CAM_IOSCHED_DYNAMIC 773 static void 774 cam_iosched_iop_stats_init(struct cam_iosched_softc *isc, struct iop_stats *ios) 775 { 776 777 ios->limiter = none; 778 ios->in = 0; 779 ios->max = ios->current = 300000; 780 ios->min = 1; 781 ios->out = 0; 782 ios->pending = 0; 783 ios->queued = 0; 784 ios->total = 0; 785 ios->ema = 0; 786 ios->emvar = 0; 787 ios->softc = isc; 788 cam_iosched_limiter_init(ios); 789 } 790 791 static int 792 cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS) 793 { 794 char buf[16]; 795 struct iop_stats *ios; 796 struct cam_iosched_softc *isc; 797 int value, i, error; 798 const char *p; 799 800 ios = arg1; 801 isc = ios->softc; 802 value = ios->limiter; 803 if (value < none || value >= limiter_max) 804 p = "UNKNOWN"; 805 else 806 p = cam_iosched_limiter_names[value]; 807 808 strlcpy(buf, p, sizeof(buf)); 809 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 810 if (error != 0 || req->newptr == NULL) 811 return error; 812 813 cam_periph_lock(isc->periph); 814 815 for (i = none; i < limiter_max; i++) { 816 if (strcmp(buf, cam_iosched_limiter_names[i]) != 0) 817 continue; 818 ios->limiter = i; 819 error = cam_iosched_limiter_init(ios); 820 if (error != 0) { 821 ios->limiter = value; 822 cam_periph_unlock(isc->periph); 823 return error; 824 } 825 /* Note: disk load averate requires ticker to be always running */ 826 callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc); 827 isc->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 828 829 cam_periph_unlock(isc->periph); 830 return 0; 831 } 832 833 cam_periph_unlock(isc->periph); 834 return EINVAL; 835 } 836 837 static int 838 cam_iosched_control_type_sysctl(SYSCTL_HANDLER_ARGS) 839 { 840 char buf[16]; 841 struct control_loop *clp; 842 struct cam_iosched_softc *isc; 843 int value, i, error; 844 const char *p; 845 846 clp = arg1; 847 isc = clp->softc; 848 value = clp->type; 849 if (value < none || value >= cl_max) 850 p = "UNKNOWN"; 851 else 852 p = cam_iosched_control_type_names[value]; 853 854 strlcpy(buf, p, sizeof(buf)); 855 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 856 if (error != 0 || req->newptr == NULL) 857 return error; 858 859 for (i = set_max; i < cl_max; i++) { 860 if (strcmp(buf, cam_iosched_control_type_names[i]) != 0) 861 continue; 862 cam_periph_lock(isc->periph); 863 clp->type = i; 864 cam_periph_unlock(isc->periph); 865 return 0; 866 } 867 868 return EINVAL; 869 } 870 871 static int 872 cam_iosched_sbintime_sysctl(SYSCTL_HANDLER_ARGS) 873 { 874 char buf[16]; 875 sbintime_t value; 876 int error; 877 uint64_t us; 878 879 value = *(sbintime_t *)arg1; 880 us = (uint64_t)value / SBT_1US; 881 snprintf(buf, sizeof(buf), "%ju", (intmax_t)us); 882 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 883 if (error != 0 || req->newptr == NULL) 884 return error; 885 us = strtoul(buf, NULL, 10); 886 if (us == 0) 887 return EINVAL; 888 *(sbintime_t *)arg1 = us * SBT_1US; 889 return 0; 890 } 891 892 static int 893 cam_iosched_sysctl_latencies(SYSCTL_HANDLER_ARGS) 894 { 895 int i, error; 896 struct sbuf sb; 897 uint64_t *latencies; 898 899 latencies = arg1; 900 sbuf_new_for_sysctl(&sb, NULL, LAT_BUCKETS * 16, req); 901 902 for (i = 0; i < LAT_BUCKETS - 1; i++) 903 sbuf_printf(&sb, "%jd,", (intmax_t)latencies[i]); 904 sbuf_printf(&sb, "%jd", (intmax_t)latencies[LAT_BUCKETS - 1]); 905 error = sbuf_finish(&sb); 906 sbuf_delete(&sb); 907 908 return (error); 909 } 910 911 static int 912 cam_iosched_quanta_sysctl(SYSCTL_HANDLER_ARGS) 913 { 914 int *quanta; 915 int error, value; 916 917 quanta = (unsigned *)arg1; 918 value = *quanta; 919 920 error = sysctl_handle_int(oidp, (int *)&value, 0, req); 921 if ((error != 0) || (req->newptr == NULL)) 922 return (error); 923 924 if (value < 1 || value > hz) 925 return (EINVAL); 926 927 *quanta = value; 928 929 return (0); 930 } 931 932 static void 933 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct iop_stats *ios, char *name) 934 { 935 struct sysctl_oid_list *n; 936 struct sysctl_ctx_list *ctx; 937 938 ios->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 939 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, name, 940 CTLFLAG_RD, 0, name); 941 n = SYSCTL_CHILDREN(ios->sysctl_tree); 942 ctx = &ios->sysctl_ctx; 943 944 SYSCTL_ADD_UQUAD(ctx, n, 945 OID_AUTO, "ema", CTLFLAG_RD, 946 &ios->ema, 947 "Fast Exponentially Weighted Moving Average"); 948 SYSCTL_ADD_UQUAD(ctx, n, 949 OID_AUTO, "emvar", CTLFLAG_RD, 950 &ios->emvar, 951 "Fast Exponentially Weighted Moving Variance"); 952 953 SYSCTL_ADD_INT(ctx, n, 954 OID_AUTO, "pending", CTLFLAG_RD, 955 &ios->pending, 0, 956 "Instantaneous # of pending transactions"); 957 SYSCTL_ADD_INT(ctx, n, 958 OID_AUTO, "count", CTLFLAG_RD, 959 &ios->total, 0, 960 "# of transactions submitted to hardware"); 961 SYSCTL_ADD_INT(ctx, n, 962 OID_AUTO, "queued", CTLFLAG_RD, 963 &ios->queued, 0, 964 "# of transactions in the queue"); 965 SYSCTL_ADD_INT(ctx, n, 966 OID_AUTO, "in", CTLFLAG_RD, 967 &ios->in, 0, 968 "# of transactions queued to driver"); 969 SYSCTL_ADD_INT(ctx, n, 970 OID_AUTO, "out", CTLFLAG_RD, 971 &ios->out, 0, 972 "# of transactions completed"); 973 974 SYSCTL_ADD_PROC(ctx, n, 975 OID_AUTO, "limiter", CTLTYPE_STRING | CTLFLAG_RW, 976 ios, 0, cam_iosched_limiter_sysctl, "A", 977 "Current limiting type."); 978 SYSCTL_ADD_INT(ctx, n, 979 OID_AUTO, "min", CTLFLAG_RW, 980 &ios->min, 0, 981 "min resource"); 982 SYSCTL_ADD_INT(ctx, n, 983 OID_AUTO, "max", CTLFLAG_RW, 984 &ios->max, 0, 985 "max resource"); 986 SYSCTL_ADD_INT(ctx, n, 987 OID_AUTO, "current", CTLFLAG_RW, 988 &ios->current, 0, 989 "current resource"); 990 991 SYSCTL_ADD_PROC(ctx, n, 992 OID_AUTO, "latencies", CTLTYPE_STRING | CTLFLAG_RD, 993 &ios->latencies, 0, 994 cam_iosched_sysctl_latencies, "A", 995 "Array of power of 2 latency from 1ms to 1.024s"); 996 } 997 998 static void 999 cam_iosched_iop_stats_fini(struct iop_stats *ios) 1000 { 1001 if (ios->sysctl_tree) 1002 if (sysctl_ctx_free(&ios->sysctl_ctx) != 0) 1003 printf("can't remove iosched sysctl stats context\n"); 1004 } 1005 1006 static void 1007 cam_iosched_cl_sysctl_init(struct cam_iosched_softc *isc) 1008 { 1009 struct sysctl_oid_list *n; 1010 struct sysctl_ctx_list *ctx; 1011 struct control_loop *clp; 1012 1013 clp = &isc->cl; 1014 clp->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1015 SYSCTL_CHILDREN(isc->sysctl_tree), OID_AUTO, "control", 1016 CTLFLAG_RD, 0, "Control loop info"); 1017 n = SYSCTL_CHILDREN(clp->sysctl_tree); 1018 ctx = &clp->sysctl_ctx; 1019 1020 SYSCTL_ADD_PROC(ctx, n, 1021 OID_AUTO, "type", CTLTYPE_STRING | CTLFLAG_RW, 1022 clp, 0, cam_iosched_control_type_sysctl, "A", 1023 "Control loop algorithm"); 1024 SYSCTL_ADD_PROC(ctx, n, 1025 OID_AUTO, "steer_interval", CTLTYPE_STRING | CTLFLAG_RW, 1026 &clp->steer_interval, 0, cam_iosched_sbintime_sysctl, "A", 1027 "How often to steer (in us)"); 1028 SYSCTL_ADD_PROC(ctx, n, 1029 OID_AUTO, "lolat", CTLTYPE_STRING | CTLFLAG_RW, 1030 &clp->lolat, 0, cam_iosched_sbintime_sysctl, "A", 1031 "Low water mark for Latency (in us)"); 1032 SYSCTL_ADD_PROC(ctx, n, 1033 OID_AUTO, "hilat", CTLTYPE_STRING | CTLFLAG_RW, 1034 &clp->hilat, 0, cam_iosched_sbintime_sysctl, "A", 1035 "Hi water mark for Latency (in us)"); 1036 SYSCTL_ADD_INT(ctx, n, 1037 OID_AUTO, "alpha", CTLFLAG_RW, 1038 &clp->alpha, 0, 1039 "Alpha for PLL (x100) aka gain"); 1040 } 1041 1042 static void 1043 cam_iosched_cl_sysctl_fini(struct control_loop *clp) 1044 { 1045 if (clp->sysctl_tree) 1046 if (sysctl_ctx_free(&clp->sysctl_ctx) != 0) 1047 printf("can't remove iosched sysctl control loop context\n"); 1048 } 1049 #endif 1050 1051 /* 1052 * Allocate the iosched structure. This also insulates callers from knowing 1053 * sizeof struct cam_iosched_softc. 1054 */ 1055 int 1056 cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph) 1057 { 1058 1059 *iscp = malloc(sizeof(**iscp), M_CAMSCHED, M_NOWAIT | M_ZERO); 1060 if (*iscp == NULL) 1061 return ENOMEM; 1062 #ifdef CAM_IOSCHED_DYNAMIC 1063 if (iosched_debug) 1064 printf("CAM IOSCHEDULER Allocating entry at %p\n", *iscp); 1065 #endif 1066 (*iscp)->sort_io_queue = -1; 1067 bioq_init(&(*iscp)->bio_queue); 1068 bioq_init(&(*iscp)->trim_queue); 1069 #ifdef CAM_IOSCHED_DYNAMIC 1070 if (do_dynamic_iosched) { 1071 bioq_init(&(*iscp)->write_queue); 1072 (*iscp)->read_bias = 100; 1073 (*iscp)->current_read_bias = 100; 1074 (*iscp)->quanta = min(hz, 200); 1075 cam_iosched_iop_stats_init(*iscp, &(*iscp)->read_stats); 1076 cam_iosched_iop_stats_init(*iscp, &(*iscp)->write_stats); 1077 cam_iosched_iop_stats_init(*iscp, &(*iscp)->trim_stats); 1078 (*iscp)->trim_stats.max = 1; /* Trims are special: one at a time for now */ 1079 (*iscp)->last_time = sbinuptime(); 1080 callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0); 1081 (*iscp)->periph = periph; 1082 cam_iosched_cl_init(&(*iscp)->cl, *iscp); 1083 callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta, cam_iosched_ticker, *iscp); 1084 (*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1085 } 1086 #endif 1087 1088 return 0; 1089 } 1090 1091 /* 1092 * Reclaim all used resources. This assumes that other folks have 1093 * drained the requests in the hardware. Maybe an unwise assumption. 1094 */ 1095 void 1096 cam_iosched_fini(struct cam_iosched_softc *isc) 1097 { 1098 if (isc) { 1099 cam_iosched_flush(isc, NULL, ENXIO); 1100 #ifdef CAM_IOSCHED_DYNAMIC 1101 cam_iosched_iop_stats_fini(&isc->read_stats); 1102 cam_iosched_iop_stats_fini(&isc->write_stats); 1103 cam_iosched_iop_stats_fini(&isc->trim_stats); 1104 cam_iosched_cl_sysctl_fini(&isc->cl); 1105 if (isc->sysctl_tree) 1106 if (sysctl_ctx_free(&isc->sysctl_ctx) != 0) 1107 printf("can't remove iosched sysctl stats context\n"); 1108 if (isc->flags & CAM_IOSCHED_FLAG_CALLOUT_ACTIVE) { 1109 callout_drain(&isc->ticker); 1110 isc->flags &= ~ CAM_IOSCHED_FLAG_CALLOUT_ACTIVE; 1111 } 1112 #endif 1113 free(isc, M_CAMSCHED); 1114 } 1115 } 1116 1117 /* 1118 * After we're sure we're attaching a device, go ahead and add 1119 * hooks for any sysctl we may wish to honor. 1120 */ 1121 void cam_iosched_sysctl_init(struct cam_iosched_softc *isc, 1122 struct sysctl_ctx_list *ctx, struct sysctl_oid *node) 1123 { 1124 #ifdef CAM_IOSCHED_DYNAMIC 1125 struct sysctl_oid_list *n; 1126 #endif 1127 1128 SYSCTL_ADD_INT(ctx, SYSCTL_CHILDREN(node), 1129 OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE, 1130 &isc->sort_io_queue, 0, 1131 "Sort IO queue to try and optimise disk access patterns"); 1132 1133 #ifdef CAM_IOSCHED_DYNAMIC 1134 if (!do_dynamic_iosched) 1135 return; 1136 1137 isc->sysctl_tree = SYSCTL_ADD_NODE(&isc->sysctl_ctx, 1138 SYSCTL_CHILDREN(node), OID_AUTO, "iosched", 1139 CTLFLAG_RD, 0, "I/O scheduler statistics"); 1140 n = SYSCTL_CHILDREN(isc->sysctl_tree); 1141 ctx = &isc->sysctl_ctx; 1142 1143 cam_iosched_iop_stats_sysctl_init(isc, &isc->read_stats, "read"); 1144 cam_iosched_iop_stats_sysctl_init(isc, &isc->write_stats, "write"); 1145 cam_iosched_iop_stats_sysctl_init(isc, &isc->trim_stats, "trim"); 1146 cam_iosched_cl_sysctl_init(isc); 1147 1148 SYSCTL_ADD_INT(ctx, n, 1149 OID_AUTO, "read_bias", CTLFLAG_RW, 1150 &isc->read_bias, 100, 1151 "How biased towards read should we be independent of limits"); 1152 1153 SYSCTL_ADD_PROC(ctx, n, 1154 OID_AUTO, "quanta", CTLTYPE_UINT | CTLFLAG_RW, 1155 &isc->quanta, 0, cam_iosched_quanta_sysctl, "I", 1156 "How many quanta per second do we slice the I/O up into"); 1157 1158 SYSCTL_ADD_INT(ctx, n, 1159 OID_AUTO, "total_ticks", CTLFLAG_RD, 1160 &isc->total_ticks, 0, 1161 "Total number of ticks we've done"); 1162 1163 SYSCTL_ADD_INT(ctx, n, 1164 OID_AUTO, "load", CTLFLAG_RD, 1165 &isc->load, 0, 1166 "scaled load average / 100"); 1167 #endif 1168 } 1169 1170 /* 1171 * Flush outstanding I/O. Consumers of this library don't know all the 1172 * queues we may keep, so this allows all I/O to be flushed in one 1173 * convenient call. 1174 */ 1175 void 1176 cam_iosched_flush(struct cam_iosched_softc *isc, struct devstat *stp, int err) 1177 { 1178 bioq_flush(&isc->bio_queue, stp, err); 1179 bioq_flush(&isc->trim_queue, stp, err); 1180 #ifdef CAM_IOSCHED_DYNAMIC 1181 if (do_dynamic_iosched) 1182 bioq_flush(&isc->write_queue, stp, err); 1183 #endif 1184 } 1185 1186 #ifdef CAM_IOSCHED_DYNAMIC 1187 static struct bio * 1188 cam_iosched_get_write(struct cam_iosched_softc *isc) 1189 { 1190 struct bio *bp; 1191 1192 /* 1193 * We control the write rate by controlling how many requests we send 1194 * down to the drive at any one time. Fewer requests limits the 1195 * effects of both starvation when the requests take a while and write 1196 * amplification when each request is causing more than one write to 1197 * the NAND media. Limiting the queue depth like this will also limit 1198 * the write throughput and give and reads that want to compete to 1199 * compete unfairly. 1200 */ 1201 bp = bioq_first(&isc->write_queue); 1202 if (bp == NULL) { 1203 if (iosched_debug > 3) 1204 printf("No writes present in write_queue\n"); 1205 return NULL; 1206 } 1207 1208 /* 1209 * If pending read, prefer that based on current read bias 1210 * setting. 1211 */ 1212 if (bioq_first(&isc->bio_queue) && isc->current_read_bias) { 1213 if (iosched_debug) 1214 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); 1215 isc->current_read_bias--; 1216 /* We're not limiting writes, per se, just doing reads first */ 1217 return NULL; 1218 } 1219 1220 /* 1221 * See if our current limiter allows this I/O. 1222 */ 1223 if (cam_iosched_limiter_iop(&isc->write_stats, bp) != 0) { 1224 if (iosched_debug) 1225 printf("Can't write because limiter says no.\n"); 1226 isc->write_stats.state_flags |= IOP_RATE_LIMITED; 1227 return NULL; 1228 } 1229 1230 /* 1231 * Let's do this: We've passed all the gates and we're a go 1232 * to schedule the I/O in the SIM. 1233 */ 1234 isc->current_read_bias = isc->read_bias; 1235 bioq_remove(&isc->write_queue, bp); 1236 if (bp->bio_cmd == BIO_WRITE) { 1237 isc->write_stats.queued--; 1238 isc->write_stats.total++; 1239 isc->write_stats.pending++; 1240 } 1241 if (iosched_debug > 9) 1242 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1243 isc->write_stats.state_flags &= ~IOP_RATE_LIMITED; 1244 return bp; 1245 } 1246 #endif 1247 1248 /* 1249 * Put back a trim that you weren't able to actually schedule this time. 1250 */ 1251 void 1252 cam_iosched_put_back_trim(struct cam_iosched_softc *isc, struct bio *bp) 1253 { 1254 bioq_insert_head(&isc->trim_queue, bp); 1255 #ifdef CAM_IOSCHED_DYNAMIC 1256 isc->trim_stats.queued++; 1257 isc->trim_stats.total--; /* since we put it back, don't double count */ 1258 isc->trim_stats.pending--; 1259 #endif 1260 } 1261 1262 /* 1263 * gets the next trim from the trim queue. 1264 * 1265 * Assumes we're called with the periph lock held. It removes this 1266 * trim from the queue and the device must explicitly reinsert it 1267 * should the need arise. 1268 */ 1269 struct bio * 1270 cam_iosched_next_trim(struct cam_iosched_softc *isc) 1271 { 1272 struct bio *bp; 1273 1274 bp = bioq_first(&isc->trim_queue); 1275 if (bp == NULL) 1276 return NULL; 1277 bioq_remove(&isc->trim_queue, bp); 1278 #ifdef CAM_IOSCHED_DYNAMIC 1279 isc->trim_stats.queued--; 1280 isc->trim_stats.total++; 1281 isc->trim_stats.pending++; 1282 #endif 1283 return bp; 1284 } 1285 1286 /* 1287 * gets an available trim from the trim queue, if there's no trim 1288 * already pending. It removes this trim from the queue and the device 1289 * must explicitly reinsert it should the need arise. 1290 * 1291 * Assumes we're called with the periph lock held. 1292 */ 1293 struct bio * 1294 cam_iosched_get_trim(struct cam_iosched_softc *isc) 1295 { 1296 1297 if (!cam_iosched_has_more_trim(isc)) 1298 return NULL; 1299 1300 return cam_iosched_next_trim(isc); 1301 } 1302 1303 /* 1304 * Determine what the next bit of work to do is for the periph. The 1305 * default implementation looks to see if we have trims to do, but no 1306 * trims outstanding. If so, we do that. Otherwise we see if we have 1307 * other work. If we do, then we do that. Otherwise why were we called? 1308 */ 1309 struct bio * 1310 cam_iosched_next_bio(struct cam_iosched_softc *isc) 1311 { 1312 struct bio *bp; 1313 1314 /* 1315 * See if we have a trim that can be scheduled. We can only send one 1316 * at a time down, so this takes that into account. 1317 * 1318 * XXX newer TRIM commands are queueable. Revisit this when we 1319 * implement them. 1320 */ 1321 if ((bp = cam_iosched_get_trim(isc)) != NULL) 1322 return bp; 1323 1324 #ifdef CAM_IOSCHED_DYNAMIC 1325 /* 1326 * See if we have any pending writes, and room in the queue for them, 1327 * and if so, those are next. 1328 */ 1329 if (do_dynamic_iosched) { 1330 if ((bp = cam_iosched_get_write(isc)) != NULL) 1331 return bp; 1332 } 1333 #endif 1334 1335 /* 1336 * next, see if there's other, normal I/O waiting. If so return that. 1337 */ 1338 if ((bp = bioq_first(&isc->bio_queue)) == NULL) 1339 return NULL; 1340 1341 #ifdef CAM_IOSCHED_DYNAMIC 1342 /* 1343 * For the dynamic scheduler, bio_queue is only for reads, so enforce 1344 * the limits here. Enforce only for reads. 1345 */ 1346 if (do_dynamic_iosched) { 1347 if (bp->bio_cmd == BIO_READ && 1348 cam_iosched_limiter_iop(&isc->read_stats, bp) != 0) { 1349 isc->read_stats.state_flags |= IOP_RATE_LIMITED; 1350 return NULL; 1351 } 1352 } 1353 isc->read_stats.state_flags &= ~IOP_RATE_LIMITED; 1354 #endif 1355 bioq_remove(&isc->bio_queue, bp); 1356 #ifdef CAM_IOSCHED_DYNAMIC 1357 if (do_dynamic_iosched) { 1358 if (bp->bio_cmd == BIO_READ) { 1359 isc->read_stats.queued--; 1360 isc->read_stats.total++; 1361 isc->read_stats.pending++; 1362 } else 1363 printf("Found bio_cmd = %#x\n", bp->bio_cmd); 1364 } 1365 if (iosched_debug > 9) 1366 printf("HWQ : %p %#x\n", bp, bp->bio_cmd); 1367 #endif 1368 return bp; 1369 } 1370 1371 /* 1372 * Driver has been given some work to do by the block layer. Tell the 1373 * scheduler about it and have it queue the work up. The scheduler module 1374 * will then return the currently most useful bit of work later, possibly 1375 * deferring work for various reasons. 1376 */ 1377 void 1378 cam_iosched_queue_work(struct cam_iosched_softc *isc, struct bio *bp) 1379 { 1380 1381 /* 1382 * Put all trims on the trim queue sorted, since we know 1383 * that the collapsing code requires this. Otherwise put 1384 * the work on the bio queue. 1385 */ 1386 if (bp->bio_cmd == BIO_DELETE) { 1387 bioq_disksort(&isc->trim_queue, bp); 1388 #ifdef CAM_IOSCHED_DYNAMIC 1389 isc->trim_stats.in++; 1390 isc->trim_stats.queued++; 1391 #endif 1392 } 1393 #ifdef CAM_IOSCHED_DYNAMIC 1394 else if (do_dynamic_iosched && (bp->bio_cmd != BIO_READ)) { 1395 if (cam_iosched_sort_queue(isc)) 1396 bioq_disksort(&isc->write_queue, bp); 1397 else 1398 bioq_insert_tail(&isc->write_queue, bp); 1399 if (iosched_debug > 9) 1400 printf("Qw : %p %#x\n", bp, bp->bio_cmd); 1401 if (bp->bio_cmd == BIO_WRITE) { 1402 isc->write_stats.in++; 1403 isc->write_stats.queued++; 1404 } 1405 } 1406 #endif 1407 else { 1408 if (cam_iosched_sort_queue(isc)) 1409 bioq_disksort(&isc->bio_queue, bp); 1410 else 1411 bioq_insert_tail(&isc->bio_queue, bp); 1412 #ifdef CAM_IOSCHED_DYNAMIC 1413 if (iosched_debug > 9) 1414 printf("Qr : %p %#x\n", bp, bp->bio_cmd); 1415 if (bp->bio_cmd == BIO_READ) { 1416 isc->read_stats.in++; 1417 isc->read_stats.queued++; 1418 } else if (bp->bio_cmd == BIO_WRITE) { 1419 isc->write_stats.in++; 1420 isc->write_stats.queued++; 1421 } 1422 #endif 1423 } 1424 } 1425 1426 /* 1427 * If we have work, get it scheduled. Called with the periph lock held. 1428 */ 1429 void 1430 cam_iosched_schedule(struct cam_iosched_softc *isc, struct cam_periph *periph) 1431 { 1432 1433 if (cam_iosched_has_work(isc)) 1434 xpt_schedule(periph, CAM_PRIORITY_NORMAL); 1435 } 1436 1437 /* 1438 * Complete a trim request. Mark that we no longer have one in flight. 1439 */ 1440 void 1441 cam_iosched_trim_done(struct cam_iosched_softc *isc) 1442 { 1443 1444 isc->flags &= ~CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1445 } 1446 1447 /* 1448 * Complete a bio. Called before we release the ccb with xpt_release_ccb so we 1449 * might use notes in the ccb for statistics. 1450 */ 1451 int 1452 cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp, 1453 union ccb *done_ccb) 1454 { 1455 int retval = 0; 1456 #ifdef CAM_IOSCHED_DYNAMIC 1457 if (!do_dynamic_iosched) 1458 return retval; 1459 1460 if (iosched_debug > 10) 1461 printf("done: %p %#x\n", bp, bp->bio_cmd); 1462 if (bp->bio_cmd == BIO_WRITE) { 1463 retval = cam_iosched_limiter_iodone(&isc->write_stats, bp); 1464 isc->write_stats.out++; 1465 isc->write_stats.pending--; 1466 } else if (bp->bio_cmd == BIO_READ) { 1467 retval = cam_iosched_limiter_iodone(&isc->read_stats, bp); 1468 isc->read_stats.out++; 1469 isc->read_stats.pending--; 1470 } else if (bp->bio_cmd == BIO_DELETE) { 1471 isc->trim_stats.out++; 1472 isc->trim_stats.pending--; 1473 } else if (bp->bio_cmd != BIO_FLUSH) { 1474 if (iosched_debug) 1475 printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd); 1476 } 1477 1478 if (!(bp->bio_flags & BIO_ERROR)) 1479 cam_iosched_io_metric_update(isc, 1480 cam_iosched_sbintime_t(done_ccb->ccb_h.qos.periph_data), 1481 bp->bio_cmd, bp->bio_bcount); 1482 #endif 1483 return retval; 1484 } 1485 1486 /* 1487 * Tell the io scheduler that you've pushed a trim down into the sim. 1488 * This also tells the I/O scheduler not to push any more trims down, so 1489 * some periphs do not call it if they can cope with multiple trims in flight. 1490 */ 1491 void 1492 cam_iosched_submit_trim(struct cam_iosched_softc *isc) 1493 { 1494 1495 isc->flags |= CAM_IOSCHED_FLAG_TRIM_ACTIVE; 1496 } 1497 1498 /* 1499 * Change the sorting policy hint for I/O transactions for this device. 1500 */ 1501 void 1502 cam_iosched_set_sort_queue(struct cam_iosched_softc *isc, int val) 1503 { 1504 1505 isc->sort_io_queue = val; 1506 } 1507 1508 int 1509 cam_iosched_has_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1510 { 1511 return isc->flags & flags; 1512 } 1513 1514 void 1515 cam_iosched_set_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1516 { 1517 isc->flags |= flags; 1518 } 1519 1520 void 1521 cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags) 1522 { 1523 isc->flags &= ~flags; 1524 } 1525 1526 #ifdef CAM_IOSCHED_DYNAMIC 1527 /* 1528 * After the method presented in Jack Crenshaw's 1998 article "Integer 1529 * Square Roots," reprinted at 1530 * http://www.embedded.com/electronics-blogs/programmer-s-toolbox/4219659/Integer-Square-Roots 1531 * and well worth the read. Briefly, we find the power of 4 that's the 1532 * largest smaller than val. We then check each smaller power of 4 to 1533 * see if val is still bigger. The right shifts at each step divide 1534 * the result by 2 which after successive application winds up 1535 * accumulating the right answer. It could also have been accumulated 1536 * using a separate root counter, but this code is smaller and faster 1537 * than that method. This method is also integer size invariant. 1538 * It returns floor(sqrt((float)val)), or the largest integer less than 1539 * or equal to the square root. 1540 */ 1541 static uint64_t 1542 isqrt64(uint64_t val) 1543 { 1544 uint64_t res = 0; 1545 uint64_t bit = 1ULL << (sizeof(uint64_t) * NBBY - 2); 1546 1547 /* 1548 * Find the largest power of 4 smaller than val. 1549 */ 1550 while (bit > val) 1551 bit >>= 2; 1552 1553 /* 1554 * Accumulate the answer, one bit at a time (we keep moving 1555 * them over since 2 is the square root of 4 and we test 1556 * powers of 4). We accumulate where we find the bit, but 1557 * the successive shifts land the bit in the right place 1558 * by the end. 1559 */ 1560 while (bit != 0) { 1561 if (val >= res + bit) { 1562 val -= res + bit; 1563 res = (res >> 1) + bit; 1564 } else 1565 res >>= 1; 1566 bit >>= 2; 1567 } 1568 1569 return res; 1570 } 1571 1572 static sbintime_t latencies[LAT_BUCKETS - 1] = { 1573 SBT_1MS << 0, 1574 SBT_1MS << 1, 1575 SBT_1MS << 2, 1576 SBT_1MS << 3, 1577 SBT_1MS << 4, 1578 SBT_1MS << 5, 1579 SBT_1MS << 6, 1580 SBT_1MS << 7, 1581 SBT_1MS << 8, 1582 SBT_1MS << 9, 1583 SBT_1MS << 10, 1584 SBT_1MS << 11, 1585 SBT_1MS << 12, 1586 SBT_1MS << 13 /* 8.192s */ 1587 }; 1588 1589 static void 1590 cam_iosched_update(struct iop_stats *iop, sbintime_t sim_latency) 1591 { 1592 sbintime_t y, deltasq, delta; 1593 int i; 1594 1595 /* 1596 * Keep counts for latency. We do it by power of two buckets. 1597 * This helps us spot outlier behavior obscured by averages. 1598 */ 1599 for (i = 0; i < LAT_BUCKETS - 1; i++) { 1600 if (sim_latency < latencies[i]) { 1601 iop->latencies[i]++; 1602 break; 1603 } 1604 } 1605 if (i == LAT_BUCKETS - 1) 1606 iop->latencies[i]++; /* Put all > 1024ms values into the last bucket. */ 1607 1608 /* 1609 * Classic exponentially decaying average with a tiny alpha 1610 * (2 ^ -alpha_bits). For more info see the NIST statistical 1611 * handbook. 1612 * 1613 * ema_t = y_t * alpha + ema_t-1 * (1 - alpha) [nist] 1614 * ema_t = y_t * alpha + ema_t-1 - alpha * ema_t-1 1615 * ema_t = alpha * y_t - alpha * ema_t-1 + ema_t-1 1616 * alpha = 1 / (1 << alpha_bits) 1617 * sub e == ema_t-1, b == 1/alpha (== 1 << alpha_bits), d == y_t - ema_t-1 1618 * = y_t/b - e/b + be/b 1619 * = (y_t - e + be) / b 1620 * = (e + d) / b 1621 * 1622 * Since alpha is a power of two, we can compute this w/o any mult or 1623 * division. 1624 * 1625 * Variance can also be computed. Usually, it would be expressed as follows: 1626 * diff_t = y_t - ema_t-1 1627 * emvar_t = (1 - alpha) * (emavar_t-1 + diff_t^2 * alpha) 1628 * = emavar_t-1 - alpha * emavar_t-1 + delta_t^2 * alpha - (delta_t * alpha)^2 1629 * sub b == 1/alpha (== 1 << alpha_bits), e == emavar_t-1, d = delta_t^2 1630 * = e - e/b + dd/b + dd/bb 1631 * = (bbe - be + bdd + dd) / bb 1632 * = (bbe + b(dd-e) + dd) / bb (which is expanded below bb = 1<<(2*alpha_bits)) 1633 */ 1634 /* 1635 * XXX possible numeric issues 1636 * o We assume right shifted integers do the right thing, since that's 1637 * implementation defined. You can change the right shifts to / (1LL << alpha). 1638 * o alpha_bits = 9 gives ema ceiling of 23 bits of seconds for ema and 14 bits 1639 * for emvar. This puts a ceiling of 13 bits on alpha since we need a 1640 * few tens of seconds of representation. 1641 * o We mitigate alpha issues by never setting it too high. 1642 */ 1643 y = sim_latency; 1644 delta = (y - iop->ema); /* d */ 1645 iop->ema = ((iop->ema << alpha_bits) + delta) >> alpha_bits; 1646 1647 /* 1648 * Were we to naively plow ahead at this point, we wind up with many numerical 1649 * issues making any SD > ~3ms unreliable. So, we shift right by 12. This leaves 1650 * us with microsecond level precision in the input, so the same in the 1651 * output. It means we can't overflow deltasq unless delta > 4k seconds. It 1652 * also means that emvar can be up 46 bits 40 of which are fraction, which 1653 * gives us a way to measure up to ~8s in the SD before the computation goes 1654 * unstable. Even the worst hard disk rarely has > 1s service time in the 1655 * drive. It does mean we have to shift left 12 bits after taking the 1656 * square root to compute the actual standard deviation estimate. This loss of 1657 * precision is preferable to needing int128 types to work. The above numbers 1658 * assume alpha=9. 10 or 11 are ok, but we start to run into issues at 12, 1659 * so 12 or 13 is OK for EMA, EMVAR and SD will be wrong in those cases. 1660 */ 1661 delta >>= 12; 1662 deltasq = delta * delta; /* dd */ 1663 iop->emvar = ((iop->emvar << (2 * alpha_bits)) + /* bbe */ 1664 ((deltasq - iop->emvar) << alpha_bits) + /* b(dd-e) */ 1665 deltasq) /* dd */ 1666 >> (2 * alpha_bits); /* div bb */ 1667 iop->sd = (sbintime_t)isqrt64((uint64_t)iop->emvar) << 12; 1668 } 1669 1670 static void 1671 cam_iosched_io_metric_update(struct cam_iosched_softc *isc, 1672 sbintime_t sim_latency, int cmd, size_t size) 1673 { 1674 /* xxx Do we need to scale based on the size of the I/O ? */ 1675 switch (cmd) { 1676 case BIO_READ: 1677 cam_iosched_update(&isc->read_stats, sim_latency); 1678 break; 1679 case BIO_WRITE: 1680 cam_iosched_update(&isc->write_stats, sim_latency); 1681 break; 1682 case BIO_DELETE: 1683 cam_iosched_update(&isc->trim_stats, sim_latency); 1684 break; 1685 default: 1686 break; 1687 } 1688 } 1689 1690 #ifdef DDB 1691 static int biolen(struct bio_queue_head *bq) 1692 { 1693 int i = 0; 1694 struct bio *bp; 1695 1696 TAILQ_FOREACH(bp, &bq->queue, bio_queue) { 1697 i++; 1698 } 1699 return i; 1700 } 1701 1702 /* 1703 * Show the internal state of the I/O scheduler. 1704 */ 1705 DB_SHOW_COMMAND(iosched, cam_iosched_db_show) 1706 { 1707 struct cam_iosched_softc *isc; 1708 1709 if (!have_addr) { 1710 db_printf("Need addr\n"); 1711 return; 1712 } 1713 isc = (struct cam_iosched_softc *)addr; 1714 db_printf("pending_reads: %d\n", isc->read_stats.pending); 1715 db_printf("min_reads: %d\n", isc->read_stats.min); 1716 db_printf("max_reads: %d\n", isc->read_stats.max); 1717 db_printf("reads: %d\n", isc->read_stats.total); 1718 db_printf("in_reads: %d\n", isc->read_stats.in); 1719 db_printf("out_reads: %d\n", isc->read_stats.out); 1720 db_printf("queued_reads: %d\n", isc->read_stats.queued); 1721 db_printf("Current Q len %d\n", biolen(&isc->bio_queue)); 1722 db_printf("pending_writes: %d\n", isc->write_stats.pending); 1723 db_printf("min_writes: %d\n", isc->write_stats.min); 1724 db_printf("max_writes: %d\n", isc->write_stats.max); 1725 db_printf("writes: %d\n", isc->write_stats.total); 1726 db_printf("in_writes: %d\n", isc->write_stats.in); 1727 db_printf("out_writes: %d\n", isc->write_stats.out); 1728 db_printf("queued_writes: %d\n", isc->write_stats.queued); 1729 db_printf("Current Q len %d\n", biolen(&isc->write_queue)); 1730 db_printf("pending_trims: %d\n", isc->trim_stats.pending); 1731 db_printf("min_trims: %d\n", isc->trim_stats.min); 1732 db_printf("max_trims: %d\n", isc->trim_stats.max); 1733 db_printf("trims: %d\n", isc->trim_stats.total); 1734 db_printf("in_trims: %d\n", isc->trim_stats.in); 1735 db_printf("out_trims: %d\n", isc->trim_stats.out); 1736 db_printf("queued_trims: %d\n", isc->trim_stats.queued); 1737 db_printf("Current Q len %d\n", biolen(&isc->trim_queue)); 1738 db_printf("read_bias: %d\n", isc->read_bias); 1739 db_printf("current_read_bias: %d\n", isc->current_read_bias); 1740 db_printf("Trim active? %s\n", 1741 (isc->flags & CAM_IOSCHED_FLAG_TRIM_ACTIVE) ? "yes" : "no"); 1742 } 1743 #endif 1744 #endif 1745