1 /* 2 * QEMU throttling infrastructure 3 * 4 * Copyright (C) Nodalink, EURL. 2013-2014 5 * Copyright (C) Igalia, S.L. 2015 6 * 7 * Authors: 8 * Benoît Canet <benoit.canet@nodalink.com> 9 * Alberto Garcia <berto@igalia.com> 10 * 11 * This program is free software; you can redistribute it and/or 12 * modify it under the terms of the GNU General Public License as 13 * published by the Free Software Foundation; either version 2 or 14 * (at your option) version 3 of the License. 15 * 16 * This program is distributed in the hope that it will be useful, 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 * GNU General Public License for more details. 20 * 21 * You should have received a copy of the GNU General Public License 22 * along with this program; if not, see <http://www.gnu.org/licenses/>. 23 */ 24 25 #include "qemu/osdep.h" 26 #include "qapi/error.h" 27 #include "qemu/throttle.h" 28 #include "qemu/timer.h" 29 #include "block/aio.h" 30 31 /* This function make a bucket leak 32 * 33 * @bkt: the bucket to make leak 34 * @delta_ns: the time delta 35 */ 36 void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta_ns) 37 { 38 double leak; 39 40 /* compute how much to leak */ 41 leak = (bkt->avg * (double) delta_ns) / NANOSECONDS_PER_SECOND; 42 43 /* make the bucket leak */ 44 bkt->level = MAX(bkt->level - leak, 0); 45 46 /* if we allow bursts for more than one second we also need to 47 * keep track of bkt->burst_level so the bkt->max goal per second 48 * is attained */ 49 if (bkt->burst_length > 1) { 50 leak = (bkt->max * (double) delta_ns) / NANOSECONDS_PER_SECOND; 51 bkt->burst_level = MAX(bkt->burst_level - leak, 0); 52 } 53 } 54 55 /* Calculate the time delta since last leak and make proportionals leaks 56 * 57 * @now: the current timestamp in ns 58 */ 59 static void throttle_do_leak(ThrottleState *ts, int64_t now) 60 { 61 /* compute the time elapsed since the last leak */ 62 int64_t delta_ns = now - ts->previous_leak; 63 int i; 64 65 ts->previous_leak = now; 66 67 if (delta_ns <= 0) { 68 return; 69 } 70 71 /* make each bucket leak */ 72 for (i = 0; i < BUCKETS_COUNT; i++) { 73 throttle_leak_bucket(&ts->cfg.buckets[i], delta_ns); 74 } 75 } 76 77 /* do the real job of computing the time to wait 78 * 79 * @limit: the throttling limit 80 * @extra: the number of operation to delay 81 * @ret: the time to wait in ns 82 */ 83 static int64_t throttle_do_compute_wait(double limit, double extra) 84 { 85 double wait = extra * NANOSECONDS_PER_SECOND; 86 wait /= limit; 87 return wait; 88 } 89 90 /* This function compute the wait time in ns that a leaky bucket should trigger 91 * 92 * @bkt: the leaky bucket we operate on 93 * @ret: the resulting wait time in ns or 0 if the operation can go through 94 */ 95 int64_t throttle_compute_wait(LeakyBucket *bkt) 96 { 97 double extra; /* the number of extra units blocking the io */ 98 double bucket_size; /* I/O before throttling to bkt->avg */ 99 double burst_bucket_size; /* Before throttling to bkt->max */ 100 101 if (!bkt->avg) { 102 return 0; 103 } 104 105 if (!bkt->max) { 106 /* If bkt->max is 0 we still want to allow short bursts of I/O 107 * from the guest, otherwise every other request will be throttled 108 * and performance will suffer considerably. */ 109 bucket_size = (double) bkt->avg / 10; 110 burst_bucket_size = 0; 111 } else { 112 /* If we have a burst limit then we have to wait until all I/O 113 * at burst rate has finished before throttling to bkt->avg */ 114 bucket_size = bkt->max * bkt->burst_length; 115 burst_bucket_size = (double) bkt->max / 10; 116 } 117 118 /* If the main bucket is full then we have to wait */ 119 extra = bkt->level - bucket_size; 120 if (extra > 0) { 121 return throttle_do_compute_wait(bkt->avg, extra); 122 } 123 124 /* If the main bucket is not full yet we still have to check the 125 * burst bucket in order to enforce the burst limit */ 126 if (bkt->burst_length > 1) { 127 assert(bkt->max > 0); /* see throttle_is_valid() */ 128 extra = bkt->burst_level - burst_bucket_size; 129 if (extra > 0) { 130 return throttle_do_compute_wait(bkt->max, extra); 131 } 132 } 133 134 return 0; 135 } 136 137 /* This function compute the time that must be waited while this IO 138 * 139 * @is_write: true if the current IO is a write, false if it's a read 140 * @ret: time to wait 141 */ 142 static int64_t throttle_compute_wait_for(ThrottleState *ts, 143 bool is_write) 144 { 145 BucketType to_check[2][4] = { {THROTTLE_BPS_TOTAL, 146 THROTTLE_OPS_TOTAL, 147 THROTTLE_BPS_READ, 148 THROTTLE_OPS_READ}, 149 {THROTTLE_BPS_TOTAL, 150 THROTTLE_OPS_TOTAL, 151 THROTTLE_BPS_WRITE, 152 THROTTLE_OPS_WRITE}, }; 153 int64_t wait, max_wait = 0; 154 int i; 155 156 for (i = 0; i < 4; i++) { 157 BucketType index = to_check[is_write][i]; 158 wait = throttle_compute_wait(&ts->cfg.buckets[index]); 159 if (wait > max_wait) { 160 max_wait = wait; 161 } 162 } 163 164 return max_wait; 165 } 166 167 /* compute the timer for this type of operation 168 * 169 * @is_write: the type of operation 170 * @now: the current clock timestamp 171 * @next_timestamp: the resulting timer 172 * @ret: true if a timer must be set 173 */ 174 static bool throttle_compute_timer(ThrottleState *ts, 175 bool is_write, 176 int64_t now, 177 int64_t *next_timestamp) 178 { 179 int64_t wait; 180 181 /* leak proportionally to the time elapsed */ 182 throttle_do_leak(ts, now); 183 184 /* compute the wait time if any */ 185 wait = throttle_compute_wait_for(ts, is_write); 186 187 /* if the code must wait compute when the next timer should fire */ 188 if (wait) { 189 *next_timestamp = now + wait; 190 return true; 191 } 192 193 /* else no need to wait at all */ 194 *next_timestamp = now; 195 return false; 196 } 197 198 /* Add timers to event loop */ 199 void throttle_timers_attach_aio_context(ThrottleTimers *tt, 200 AioContext *new_context) 201 { 202 tt->timers[0] = aio_timer_new(new_context, tt->clock_type, SCALE_NS, 203 tt->read_timer_cb, tt->timer_opaque); 204 tt->timers[1] = aio_timer_new(new_context, tt->clock_type, SCALE_NS, 205 tt->write_timer_cb, tt->timer_opaque); 206 } 207 208 /* 209 * Initialize the ThrottleConfig structure to a valid state 210 * @cfg: the config to initialize 211 */ 212 void throttle_config_init(ThrottleConfig *cfg) 213 { 214 unsigned i; 215 memset(cfg, 0, sizeof(*cfg)); 216 for (i = 0; i < BUCKETS_COUNT; i++) { 217 cfg->buckets[i].burst_length = 1; 218 } 219 } 220 221 /* To be called first on the ThrottleState */ 222 void throttle_init(ThrottleState *ts) 223 { 224 memset(ts, 0, sizeof(ThrottleState)); 225 throttle_config_init(&ts->cfg); 226 } 227 228 /* To be called first on the ThrottleTimers */ 229 void throttle_timers_init(ThrottleTimers *tt, 230 AioContext *aio_context, 231 QEMUClockType clock_type, 232 QEMUTimerCB *read_timer_cb, 233 QEMUTimerCB *write_timer_cb, 234 void *timer_opaque) 235 { 236 memset(tt, 0, sizeof(ThrottleTimers)); 237 238 tt->clock_type = clock_type; 239 tt->read_timer_cb = read_timer_cb; 240 tt->write_timer_cb = write_timer_cb; 241 tt->timer_opaque = timer_opaque; 242 throttle_timers_attach_aio_context(tt, aio_context); 243 } 244 245 /* destroy a timer */ 246 static void throttle_timer_destroy(QEMUTimer **timer) 247 { 248 assert(*timer != NULL); 249 250 timer_del(*timer); 251 timer_free(*timer); 252 *timer = NULL; 253 } 254 255 /* Remove timers from event loop */ 256 void throttle_timers_detach_aio_context(ThrottleTimers *tt) 257 { 258 int i; 259 260 for (i = 0; i < 2; i++) { 261 throttle_timer_destroy(&tt->timers[i]); 262 } 263 } 264 265 /* To be called last on the ThrottleTimers */ 266 void throttle_timers_destroy(ThrottleTimers *tt) 267 { 268 throttle_timers_detach_aio_context(tt); 269 } 270 271 /* is any throttling timer configured */ 272 bool throttle_timers_are_initialized(ThrottleTimers *tt) 273 { 274 if (tt->timers[0]) { 275 return true; 276 } 277 278 return false; 279 } 280 281 /* Does any throttling must be done 282 * 283 * @cfg: the throttling configuration to inspect 284 * @ret: true if throttling must be done else false 285 */ 286 bool throttle_enabled(ThrottleConfig *cfg) 287 { 288 int i; 289 290 for (i = 0; i < BUCKETS_COUNT; i++) { 291 if (cfg->buckets[i].avg > 0) { 292 return true; 293 } 294 } 295 296 return false; 297 } 298 299 /* check if a throttling configuration is valid 300 * @cfg: the throttling configuration to inspect 301 * @ret: true if valid else false 302 * @errp: error object 303 */ 304 bool throttle_is_valid(ThrottleConfig *cfg, Error **errp) 305 { 306 int i; 307 bool bps_flag, ops_flag; 308 bool bps_max_flag, ops_max_flag; 309 310 bps_flag = cfg->buckets[THROTTLE_BPS_TOTAL].avg && 311 (cfg->buckets[THROTTLE_BPS_READ].avg || 312 cfg->buckets[THROTTLE_BPS_WRITE].avg); 313 314 ops_flag = cfg->buckets[THROTTLE_OPS_TOTAL].avg && 315 (cfg->buckets[THROTTLE_OPS_READ].avg || 316 cfg->buckets[THROTTLE_OPS_WRITE].avg); 317 318 bps_max_flag = cfg->buckets[THROTTLE_BPS_TOTAL].max && 319 (cfg->buckets[THROTTLE_BPS_READ].max || 320 cfg->buckets[THROTTLE_BPS_WRITE].max); 321 322 ops_max_flag = cfg->buckets[THROTTLE_OPS_TOTAL].max && 323 (cfg->buckets[THROTTLE_OPS_READ].max || 324 cfg->buckets[THROTTLE_OPS_WRITE].max); 325 326 if (bps_flag || ops_flag || bps_max_flag || ops_max_flag) { 327 error_setg(errp, "bps/iops/max total values and read/write values" 328 " cannot be used at the same time"); 329 return false; 330 } 331 332 if (cfg->op_size && 333 !cfg->buckets[THROTTLE_OPS_TOTAL].avg && 334 !cfg->buckets[THROTTLE_OPS_READ].avg && 335 !cfg->buckets[THROTTLE_OPS_WRITE].avg) { 336 error_setg(errp, "iops size requires an iops value to be set"); 337 return false; 338 } 339 340 for (i = 0; i < BUCKETS_COUNT; i++) { 341 LeakyBucket *bkt = &cfg->buckets[i]; 342 if (bkt->avg > THROTTLE_VALUE_MAX || bkt->max > THROTTLE_VALUE_MAX) { 343 error_setg(errp, "bps/iops/max values must be within [0, %lld]", 344 THROTTLE_VALUE_MAX); 345 return false; 346 } 347 348 if (!bkt->burst_length) { 349 error_setg(errp, "the burst length cannot be 0"); 350 return false; 351 } 352 353 if (bkt->burst_length > 1 && !bkt->max) { 354 error_setg(errp, "burst length set without burst rate"); 355 return false; 356 } 357 358 if (bkt->max && bkt->burst_length > THROTTLE_VALUE_MAX / bkt->max) { 359 error_setg(errp, "burst length too high for this burst rate"); 360 return false; 361 } 362 363 if (bkt->max && !bkt->avg) { 364 error_setg(errp, "bps_max/iops_max require corresponding" 365 " bps/iops values"); 366 return false; 367 } 368 369 if (bkt->max && bkt->max < bkt->avg) { 370 error_setg(errp, "bps_max/iops_max cannot be lower than bps/iops"); 371 return false; 372 } 373 } 374 375 return true; 376 } 377 378 /* Used to configure the throttle 379 * 380 * @ts: the throttle state we are working on 381 * @clock_type: the group's clock_type 382 * @cfg: the config to set 383 */ 384 void throttle_config(ThrottleState *ts, 385 QEMUClockType clock_type, 386 ThrottleConfig *cfg) 387 { 388 int i; 389 390 ts->cfg = *cfg; 391 392 /* Zero bucket level */ 393 for (i = 0; i < BUCKETS_COUNT; i++) { 394 ts->cfg.buckets[i].level = 0; 395 ts->cfg.buckets[i].burst_level = 0; 396 } 397 398 ts->previous_leak = qemu_clock_get_ns(clock_type); 399 } 400 401 /* used to get config 402 * 403 * @ts: the throttle state we are working on 404 * @cfg: the config to write 405 */ 406 void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg) 407 { 408 *cfg = ts->cfg; 409 } 410 411 412 /* Schedule the read or write timer if needed 413 * 414 * NOTE: this function is not unit tested due to it's usage of timer_mod 415 * 416 * @tt: the timers structure 417 * @is_write: the type of operation (read/write) 418 * @ret: true if the timer has been scheduled else false 419 */ 420 bool throttle_schedule_timer(ThrottleState *ts, 421 ThrottleTimers *tt, 422 bool is_write) 423 { 424 int64_t now = qemu_clock_get_ns(tt->clock_type); 425 int64_t next_timestamp; 426 bool must_wait; 427 428 must_wait = throttle_compute_timer(ts, 429 is_write, 430 now, 431 &next_timestamp); 432 433 /* request not throttled */ 434 if (!must_wait) { 435 return false; 436 } 437 438 /* request throttled and timer pending -> do nothing */ 439 if (timer_pending(tt->timers[is_write])) { 440 return true; 441 } 442 443 /* request throttled and timer not pending -> arm timer */ 444 timer_mod(tt->timers[is_write], next_timestamp); 445 return true; 446 } 447 448 /* do the accounting for this operation 449 * 450 * @is_write: the type of operation (read/write) 451 * @size: the size of the operation 452 */ 453 void throttle_account(ThrottleState *ts, bool is_write, uint64_t size) 454 { 455 const BucketType bucket_types_size[2][2] = { 456 { THROTTLE_BPS_TOTAL, THROTTLE_BPS_READ }, 457 { THROTTLE_BPS_TOTAL, THROTTLE_BPS_WRITE } 458 }; 459 const BucketType bucket_types_units[2][2] = { 460 { THROTTLE_OPS_TOTAL, THROTTLE_OPS_READ }, 461 { THROTTLE_OPS_TOTAL, THROTTLE_OPS_WRITE } 462 }; 463 double units = 1.0; 464 unsigned i; 465 466 /* if cfg.op_size is defined and smaller than size we compute unit count */ 467 if (ts->cfg.op_size && size > ts->cfg.op_size) { 468 units = (double) size / ts->cfg.op_size; 469 } 470 471 for (i = 0; i < 2; i++) { 472 LeakyBucket *bkt; 473 474 bkt = &ts->cfg.buckets[bucket_types_size[is_write][i]]; 475 bkt->level += size; 476 if (bkt->burst_length > 1) { 477 bkt->burst_level += size; 478 } 479 480 bkt = &ts->cfg.buckets[bucket_types_units[is_write][i]]; 481 bkt->level += units; 482 if (bkt->burst_length > 1) { 483 bkt->burst_level += units; 484 } 485 } 486 } 487 488 /* return a ThrottleConfig based on the options in a ThrottleLimits 489 * 490 * @arg: the ThrottleLimits object to read from 491 * @cfg: the ThrottleConfig to edit 492 * @errp: error object 493 */ 494 void throttle_limits_to_config(ThrottleLimits *arg, ThrottleConfig *cfg, 495 Error **errp) 496 { 497 if (arg->has_bps_total) { 498 cfg->buckets[THROTTLE_BPS_TOTAL].avg = arg->bps_total; 499 } 500 if (arg->has_bps_read) { 501 cfg->buckets[THROTTLE_BPS_READ].avg = arg->bps_read; 502 } 503 if (arg->has_bps_write) { 504 cfg->buckets[THROTTLE_BPS_WRITE].avg = arg->bps_write; 505 } 506 507 if (arg->has_iops_total) { 508 cfg->buckets[THROTTLE_OPS_TOTAL].avg = arg->iops_total; 509 } 510 if (arg->has_iops_read) { 511 cfg->buckets[THROTTLE_OPS_READ].avg = arg->iops_read; 512 } 513 if (arg->has_iops_write) { 514 cfg->buckets[THROTTLE_OPS_WRITE].avg = arg->iops_write; 515 } 516 517 if (arg->has_bps_total_max) { 518 cfg->buckets[THROTTLE_BPS_TOTAL].max = arg->bps_total_max; 519 } 520 if (arg->has_bps_read_max) { 521 cfg->buckets[THROTTLE_BPS_READ].max = arg->bps_read_max; 522 } 523 if (arg->has_bps_write_max) { 524 cfg->buckets[THROTTLE_BPS_WRITE].max = arg->bps_write_max; 525 } 526 if (arg->has_iops_total_max) { 527 cfg->buckets[THROTTLE_OPS_TOTAL].max = arg->iops_total_max; 528 } 529 if (arg->has_iops_read_max) { 530 cfg->buckets[THROTTLE_OPS_READ].max = arg->iops_read_max; 531 } 532 if (arg->has_iops_write_max) { 533 cfg->buckets[THROTTLE_OPS_WRITE].max = arg->iops_write_max; 534 } 535 536 if (arg->has_bps_total_max_length) { 537 if (arg->bps_total_max_length > UINT_MAX) { 538 error_setg(errp, "bps-total-max-length value must be in" 539 " the range [0, %u]", UINT_MAX); 540 return; 541 } 542 cfg->buckets[THROTTLE_BPS_TOTAL].burst_length = arg->bps_total_max_length; 543 } 544 if (arg->has_bps_read_max_length) { 545 if (arg->bps_read_max_length > UINT_MAX) { 546 error_setg(errp, "bps-read-max-length value must be in" 547 " the range [0, %u]", UINT_MAX); 548 return; 549 } 550 cfg->buckets[THROTTLE_BPS_READ].burst_length = arg->bps_read_max_length; 551 } 552 if (arg->has_bps_write_max_length) { 553 if (arg->bps_write_max_length > UINT_MAX) { 554 error_setg(errp, "bps-write-max-length value must be in" 555 " the range [0, %u]", UINT_MAX); 556 return; 557 } 558 cfg->buckets[THROTTLE_BPS_WRITE].burst_length = arg->bps_write_max_length; 559 } 560 if (arg->has_iops_total_max_length) { 561 if (arg->iops_total_max_length > UINT_MAX) { 562 error_setg(errp, "iops-total-max-length value must be in" 563 " the range [0, %u]", UINT_MAX); 564 return; 565 } 566 cfg->buckets[THROTTLE_OPS_TOTAL].burst_length = arg->iops_total_max_length; 567 } 568 if (arg->has_iops_read_max_length) { 569 if (arg->iops_read_max_length > UINT_MAX) { 570 error_setg(errp, "iops-read-max-length value must be in" 571 " the range [0, %u]", UINT_MAX); 572 return; 573 } 574 cfg->buckets[THROTTLE_OPS_READ].burst_length = arg->iops_read_max_length; 575 } 576 if (arg->has_iops_write_max_length) { 577 if (arg->iops_write_max_length > UINT_MAX) { 578 error_setg(errp, "iops-write-max-length value must be in" 579 " the range [0, %u]", UINT_MAX); 580 return; 581 } 582 cfg->buckets[THROTTLE_OPS_WRITE].burst_length = arg->iops_write_max_length; 583 } 584 585 if (arg->has_iops_size) { 586 cfg->op_size = arg->iops_size; 587 } 588 589 throttle_is_valid(cfg, errp); 590 } 591 592 /* write the options of a ThrottleConfig to a ThrottleLimits 593 * 594 * @cfg: the ThrottleConfig to read from 595 * @var: the ThrottleLimits to write to 596 */ 597 void throttle_config_to_limits(ThrottleConfig *cfg, ThrottleLimits *var) 598 { 599 var->bps_total = cfg->buckets[THROTTLE_BPS_TOTAL].avg; 600 var->bps_read = cfg->buckets[THROTTLE_BPS_READ].avg; 601 var->bps_write = cfg->buckets[THROTTLE_BPS_WRITE].avg; 602 var->iops_total = cfg->buckets[THROTTLE_OPS_TOTAL].avg; 603 var->iops_read = cfg->buckets[THROTTLE_OPS_READ].avg; 604 var->iops_write = cfg->buckets[THROTTLE_OPS_WRITE].avg; 605 var->bps_total_max = cfg->buckets[THROTTLE_BPS_TOTAL].max; 606 var->bps_read_max = cfg->buckets[THROTTLE_BPS_READ].max; 607 var->bps_write_max = cfg->buckets[THROTTLE_BPS_WRITE].max; 608 var->iops_total_max = cfg->buckets[THROTTLE_OPS_TOTAL].max; 609 var->iops_read_max = cfg->buckets[THROTTLE_OPS_READ].max; 610 var->iops_write_max = cfg->buckets[THROTTLE_OPS_WRITE].max; 611 var->bps_total_max_length = cfg->buckets[THROTTLE_BPS_TOTAL].burst_length; 612 var->bps_read_max_length = cfg->buckets[THROTTLE_BPS_READ].burst_length; 613 var->bps_write_max_length = cfg->buckets[THROTTLE_BPS_WRITE].burst_length; 614 var->iops_total_max_length = cfg->buckets[THROTTLE_OPS_TOTAL].burst_length; 615 var->iops_read_max_length = cfg->buckets[THROTTLE_OPS_READ].burst_length; 616 var->iops_write_max_length = cfg->buckets[THROTTLE_OPS_WRITE].burst_length; 617 var->iops_size = cfg->op_size; 618 619 var->has_bps_total = true; 620 var->has_bps_read = true; 621 var->has_bps_write = true; 622 var->has_iops_total = true; 623 var->has_iops_read = true; 624 var->has_iops_write = true; 625 var->has_bps_total_max = true; 626 var->has_bps_read_max = true; 627 var->has_bps_write_max = true; 628 var->has_iops_total_max = true; 629 var->has_iops_read_max = true; 630 var->has_iops_write_max = true; 631 var->has_bps_read_max_length = true; 632 var->has_bps_total_max_length = true; 633 var->has_bps_write_max_length = true; 634 var->has_iops_total_max_length = true; 635 var->has_iops_read_max_length = true; 636 var->has_iops_write_max_length = true; 637 var->has_iops_size = true; 638 } 639