1 /* SPDX-License-Identifier: GPL-2.0 2 * 3 * IO cost model based controller. 4 * 5 * Copyright (C) 2019 Tejun Heo <tj@kernel.org> 6 * Copyright (C) 2019 Andy Newell <newella@fb.com> 7 * Copyright (C) 2019 Facebook 8 * 9 * One challenge of controlling IO resources is the lack of trivially 10 * observable cost metric. This is distinguished from CPU and memory where 11 * wallclock time and the number of bytes can serve as accurate enough 12 * approximations. 13 * 14 * Bandwidth and iops are the most commonly used metrics for IO devices but 15 * depending on the type and specifics of the device, different IO patterns 16 * easily lead to multiple orders of magnitude variations rendering them 17 * useless for the purpose of IO capacity distribution. While on-device 18 * time, with a lot of clutches, could serve as a useful approximation for 19 * non-queued rotational devices, this is no longer viable with modern 20 * devices, even the rotational ones. 21 * 22 * While there is no cost metric we can trivially observe, it isn't a 23 * complete mystery. For example, on a rotational device, seek cost 24 * dominates while a contiguous transfer contributes a smaller amount 25 * proportional to the size. If we can characterize at least the relative 26 * costs of these different types of IOs, it should be possible to 27 * implement a reasonable work-conserving proportional IO resource 28 * distribution. 29 * 30 * 1. IO Cost Model 31 * 32 * IO cost model estimates the cost of an IO given its basic parameters and 33 * history (e.g. the end sector of the last IO). The cost is measured in 34 * device time. If a given IO is estimated to cost 10ms, the device should 35 * be able to process ~100 of those IOs in a second. 36 * 37 * Currently, there's only one builtin cost model - linear. Each IO is 38 * classified as sequential or random and given a base cost accordingly. 39 * On top of that, a size cost proportional to the length of the IO is 40 * added. While simple, this model captures the operational 41 * characteristics of a wide varienty of devices well enough. Default 42 * paramters for several different classes of devices are provided and the 43 * parameters can be configured from userspace via 44 * /sys/fs/cgroup/io.cost.model. 45 * 46 * If needed, tools/cgroup/iocost_coef_gen.py can be used to generate 47 * device-specific coefficients. 48 * 49 * If needed, tools/cgroup/iocost_coef_gen.py can be used to generate 50 * device-specific coefficients. 51 * 52 * 2. Control Strategy 53 * 54 * The device virtual time (vtime) is used as the primary control metric. 55 * The control strategy is composed of the following three parts. 56 * 57 * 2-1. Vtime Distribution 58 * 59 * When a cgroup becomes active in terms of IOs, its hierarchical share is 60 * calculated. Please consider the following hierarchy where the numbers 61 * inside parentheses denote the configured weights. 62 * 63 * root 64 * / \ 65 * A (w:100) B (w:300) 66 * / \ 67 * A0 (w:100) A1 (w:100) 68 * 69 * If B is idle and only A0 and A1 are actively issuing IOs, as the two are 70 * of equal weight, each gets 50% share. If then B starts issuing IOs, B 71 * gets 300/(100+300) or 75% share, and A0 and A1 equally splits the rest, 72 * 12.5% each. The distribution mechanism only cares about these flattened 73 * shares. They're called hweights (hierarchical weights) and always add 74 * upto 1 (HWEIGHT_WHOLE). 75 * 76 * A given cgroup's vtime runs slower in inverse proportion to its hweight. 77 * For example, with 12.5% weight, A0's time runs 8 times slower (100/12.5) 78 * against the device vtime - an IO which takes 10ms on the underlying 79 * device is considered to take 80ms on A0. 80 * 81 * This constitutes the basis of IO capacity distribution. Each cgroup's 82 * vtime is running at a rate determined by its hweight. A cgroup tracks 83 * the vtime consumed by past IOs and can issue a new IO iff doing so 84 * wouldn't outrun the current device vtime. Otherwise, the IO is 85 * suspended until the vtime has progressed enough to cover it. 86 * 87 * 2-2. Vrate Adjustment 88 * 89 * It's unrealistic to expect the cost model to be perfect. There are too 90 * many devices and even on the same device the overall performance 91 * fluctuates depending on numerous factors such as IO mixture and device 92 * internal garbage collection. The controller needs to adapt dynamically. 93 * 94 * This is achieved by adjusting the overall IO rate according to how busy 95 * the device is. If the device becomes overloaded, we're sending down too 96 * many IOs and should generally slow down. If there are waiting issuers 97 * but the device isn't saturated, we're issuing too few and should 98 * generally speed up. 99 * 100 * To slow down, we lower the vrate - the rate at which the device vtime 101 * passes compared to the wall clock. For example, if the vtime is running 102 * at the vrate of 75%, all cgroups added up would only be able to issue 103 * 750ms worth of IOs per second, and vice-versa for speeding up. 104 * 105 * Device business is determined using two criteria - rq wait and 106 * completion latencies. 107 * 108 * When a device gets saturated, the on-device and then the request queues 109 * fill up and a bio which is ready to be issued has to wait for a request 110 * to become available. When this delay becomes noticeable, it's a clear 111 * indication that the device is saturated and we lower the vrate. This 112 * saturation signal is fairly conservative as it only triggers when both 113 * hardware and software queues are filled up, and is used as the default 114 * busy signal. 115 * 116 * As devices can have deep queues and be unfair in how the queued commands 117 * are executed, soley depending on rq wait may not result in satisfactory 118 * control quality. For a better control quality, completion latency QoS 119 * parameters can be configured so that the device is considered saturated 120 * if N'th percentile completion latency rises above the set point. 121 * 122 * The completion latency requirements are a function of both the 123 * underlying device characteristics and the desired IO latency quality of 124 * service. There is an inherent trade-off - the tighter the latency QoS, 125 * the higher the bandwidth lossage. Latency QoS is disabled by default 126 * and can be set through /sys/fs/cgroup/io.cost.qos. 127 * 128 * 2-3. Work Conservation 129 * 130 * Imagine two cgroups A and B with equal weights. A is issuing a small IO 131 * periodically while B is sending out enough parallel IOs to saturate the 132 * device on its own. Let's say A's usage amounts to 100ms worth of IO 133 * cost per second, i.e., 10% of the device capacity. The naive 134 * distribution of half and half would lead to 60% utilization of the 135 * device, a significant reduction in the total amount of work done 136 * compared to free-for-all competition. This is too high a cost to pay 137 * for IO control. 138 * 139 * To conserve the total amount of work done, we keep track of how much 140 * each active cgroup is actually using and yield part of its weight if 141 * there are other cgroups which can make use of it. In the above case, 142 * A's weight will be lowered so that it hovers above the actual usage and 143 * B would be able to use the rest. 144 * 145 * As we don't want to penalize a cgroup for donating its weight, the 146 * surplus weight adjustment factors in a margin and has an immediate 147 * snapback mechanism in case the cgroup needs more IO vtime for itself. 148 * 149 * Note that adjusting down surplus weights has the same effects as 150 * accelerating vtime for other cgroups and work conservation can also be 151 * implemented by adjusting vrate dynamically. However, squaring who can 152 * donate and should take back how much requires hweight propagations 153 * anyway making it easier to implement and understand as a separate 154 * mechanism. 155 * 156 * 3. Monitoring 157 * 158 * Instead of debugfs or other clumsy monitoring mechanisms, this 159 * controller uses a drgn based monitoring script - 160 * tools/cgroup/iocost_monitor.py. For details on drgn, please see 161 * https://github.com/osandov/drgn. The ouput looks like the following. 162 * 163 * sdb RUN per=300ms cur_per=234.218:v203.695 busy= +1 vrate= 62.12% 164 * active weight hweight% inflt% dbt delay usages% 165 * test/a * 50/ 50 33.33/ 33.33 27.65 2 0*041 033:033:033 166 * test/b * 100/ 100 66.67/ 66.67 17.56 0 0*000 066:079:077 167 * 168 * - per : Timer period 169 * - cur_per : Internal wall and device vtime clock 170 * - vrate : Device virtual time rate against wall clock 171 * - weight : Surplus-adjusted and configured weights 172 * - hweight : Surplus-adjusted and configured hierarchical weights 173 * - inflt : The percentage of in-flight IO cost at the end of last period 174 * - del_ms : Deferred issuer delay induction level and duration 175 * - usages : Usage history 176 */ 177 178 #include <linux/kernel.h> 179 #include <linux/module.h> 180 #include <linux/timer.h> 181 #include <linux/time64.h> 182 #include <linux/parser.h> 183 #include <linux/sched/signal.h> 184 #include <linux/blk-cgroup.h> 185 #include "blk-rq-qos.h" 186 #include "blk-stat.h" 187 #include "blk-wbt.h" 188 189 #ifdef CONFIG_TRACEPOINTS 190 191 /* copied from TRACE_CGROUP_PATH, see cgroup-internal.h */ 192 #define TRACE_IOCG_PATH_LEN 1024 193 static DEFINE_SPINLOCK(trace_iocg_path_lock); 194 static char trace_iocg_path[TRACE_IOCG_PATH_LEN]; 195 196 #define TRACE_IOCG_PATH(type, iocg, ...) \ 197 do { \ 198 unsigned long flags; \ 199 if (trace_iocost_##type##_enabled()) { \ 200 spin_lock_irqsave(&trace_iocg_path_lock, flags); \ 201 cgroup_path(iocg_to_blkg(iocg)->blkcg->css.cgroup, \ 202 trace_iocg_path, TRACE_IOCG_PATH_LEN); \ 203 trace_iocost_##type(iocg, trace_iocg_path, \ 204 ##__VA_ARGS__); \ 205 spin_unlock_irqrestore(&trace_iocg_path_lock, flags); \ 206 } \ 207 } while (0) 208 209 #else /* CONFIG_TRACE_POINTS */ 210 #define TRACE_IOCG_PATH(type, iocg, ...) do { } while (0) 211 #endif /* CONFIG_TRACE_POINTS */ 212 213 enum { 214 MILLION = 1000000, 215 216 /* timer period is calculated from latency requirements, bound it */ 217 MIN_PERIOD = USEC_PER_MSEC, 218 MAX_PERIOD = USEC_PER_SEC, 219 220 /* 221 * A cgroup's vtime can run 50% behind the device vtime, which 222 * serves as its IO credit buffer. Surplus weight adjustment is 223 * immediately canceled if the vtime margin runs below 10%. 224 */ 225 MARGIN_PCT = 50, 226 INUSE_MARGIN_PCT = 10, 227 228 /* Have some play in waitq timer operations */ 229 WAITQ_TIMER_MARGIN_PCT = 5, 230 231 /* 232 * vtime can wrap well within a reasonable uptime when vrate is 233 * consistently raised. Don't trust recorded cgroup vtime if the 234 * period counter indicates that it's older than 5mins. 235 */ 236 VTIME_VALID_DUR = 300 * USEC_PER_SEC, 237 238 /* 239 * Remember the past three non-zero usages and use the max for 240 * surplus calculation. Three slots guarantee that we remember one 241 * full period usage from the last active stretch even after 242 * partial deactivation and re-activation periods. Don't start 243 * giving away weight before collecting two data points to prevent 244 * hweight adjustments based on one partial activation period. 245 */ 246 NR_USAGE_SLOTS = 3, 247 MIN_VALID_USAGES = 2, 248 249 /* 1/64k is granular enough and can easily be handled w/ u32 */ 250 HWEIGHT_WHOLE = 1 << 16, 251 252 /* 253 * As vtime is used to calculate the cost of each IO, it needs to 254 * be fairly high precision. For example, it should be able to 255 * represent the cost of a single page worth of discard with 256 * suffificient accuracy. At the same time, it should be able to 257 * represent reasonably long enough durations to be useful and 258 * convenient during operation. 259 * 260 * 1s worth of vtime is 2^37. This gives us both sub-nanosecond 261 * granularity and days of wrap-around time even at extreme vrates. 262 */ 263 VTIME_PER_SEC_SHIFT = 37, 264 VTIME_PER_SEC = 1LLU << VTIME_PER_SEC_SHIFT, 265 VTIME_PER_USEC = VTIME_PER_SEC / USEC_PER_SEC, 266 267 /* bound vrate adjustments within two orders of magnitude */ 268 VRATE_MIN_PPM = 10000, /* 1% */ 269 VRATE_MAX_PPM = 100000000, /* 10000% */ 270 271 VRATE_MIN = VTIME_PER_USEC * VRATE_MIN_PPM / MILLION, 272 VRATE_CLAMP_ADJ_PCT = 4, 273 274 /* if IOs end up waiting for requests, issue less */ 275 RQ_WAIT_BUSY_PCT = 5, 276 277 /* unbusy hysterisis */ 278 UNBUSY_THR_PCT = 75, 279 280 /* don't let cmds which take a very long time pin lagging for too long */ 281 MAX_LAGGING_PERIODS = 10, 282 283 /* 284 * If usage% * 1.25 + 2% is lower than hweight% by more than 3%, 285 * donate the surplus. 286 */ 287 SURPLUS_SCALE_PCT = 125, /* * 125% */ 288 SURPLUS_SCALE_ABS = HWEIGHT_WHOLE / 50, /* + 2% */ 289 SURPLUS_MIN_ADJ_DELTA = HWEIGHT_WHOLE / 33, /* 3% */ 290 291 /* switch iff the conditions are met for longer than this */ 292 AUTOP_CYCLE_NSEC = 10LLU * NSEC_PER_SEC, 293 294 /* 295 * Count IO size in 4k pages. The 12bit shift helps keeping 296 * size-proportional components of cost calculation in closer 297 * numbers of digits to per-IO cost components. 298 */ 299 IOC_PAGE_SHIFT = 12, 300 IOC_PAGE_SIZE = 1 << IOC_PAGE_SHIFT, 301 IOC_SECT_TO_PAGE_SHIFT = IOC_PAGE_SHIFT - SECTOR_SHIFT, 302 303 /* if apart further than 16M, consider randio for linear model */ 304 LCOEF_RANDIO_PAGES = 4096, 305 }; 306 307 enum ioc_running { 308 IOC_IDLE, 309 IOC_RUNNING, 310 IOC_STOP, 311 }; 312 313 /* io.cost.qos controls including per-dev enable of the whole controller */ 314 enum { 315 QOS_ENABLE, 316 QOS_CTRL, 317 NR_QOS_CTRL_PARAMS, 318 }; 319 320 /* io.cost.qos params */ 321 enum { 322 QOS_RPPM, 323 QOS_RLAT, 324 QOS_WPPM, 325 QOS_WLAT, 326 QOS_MIN, 327 QOS_MAX, 328 NR_QOS_PARAMS, 329 }; 330 331 /* io.cost.model controls */ 332 enum { 333 COST_CTRL, 334 COST_MODEL, 335 NR_COST_CTRL_PARAMS, 336 }; 337 338 /* builtin linear cost model coefficients */ 339 enum { 340 I_LCOEF_RBPS, 341 I_LCOEF_RSEQIOPS, 342 I_LCOEF_RRANDIOPS, 343 I_LCOEF_WBPS, 344 I_LCOEF_WSEQIOPS, 345 I_LCOEF_WRANDIOPS, 346 NR_I_LCOEFS, 347 }; 348 349 enum { 350 LCOEF_RPAGE, 351 LCOEF_RSEQIO, 352 LCOEF_RRANDIO, 353 LCOEF_WPAGE, 354 LCOEF_WSEQIO, 355 LCOEF_WRANDIO, 356 NR_LCOEFS, 357 }; 358 359 enum { 360 AUTOP_INVALID, 361 AUTOP_HDD, 362 AUTOP_SSD_QD1, 363 AUTOP_SSD_DFL, 364 AUTOP_SSD_FAST, 365 }; 366 367 struct ioc_gq; 368 369 struct ioc_params { 370 u32 qos[NR_QOS_PARAMS]; 371 u64 i_lcoefs[NR_I_LCOEFS]; 372 u64 lcoefs[NR_LCOEFS]; 373 u32 too_fast_vrate_pct; 374 u32 too_slow_vrate_pct; 375 }; 376 377 struct ioc_missed { 378 u32 nr_met; 379 u32 nr_missed; 380 u32 last_met; 381 u32 last_missed; 382 }; 383 384 struct ioc_pcpu_stat { 385 struct ioc_missed missed[2]; 386 387 u64 rq_wait_ns; 388 u64 last_rq_wait_ns; 389 }; 390 391 /* per device */ 392 struct ioc { 393 struct rq_qos rqos; 394 395 bool enabled; 396 397 struct ioc_params params; 398 u32 period_us; 399 u32 margin_us; 400 u64 vrate_min; 401 u64 vrate_max; 402 403 spinlock_t lock; 404 struct timer_list timer; 405 struct list_head active_iocgs; /* active cgroups */ 406 struct ioc_pcpu_stat __percpu *pcpu_stat; 407 408 enum ioc_running running; 409 atomic64_t vtime_rate; 410 411 seqcount_t period_seqcount; 412 u32 period_at; /* wallclock starttime */ 413 u64 period_at_vtime; /* vtime starttime */ 414 415 atomic64_t cur_period; /* inc'd each period */ 416 int busy_level; /* saturation history */ 417 418 u64 inuse_margin_vtime; 419 bool weights_updated; 420 atomic_t hweight_gen; /* for lazy hweights */ 421 422 u64 autop_too_fast_at; 423 u64 autop_too_slow_at; 424 int autop_idx; 425 bool user_qos_params:1; 426 bool user_cost_model:1; 427 }; 428 429 /* per device-cgroup pair */ 430 struct ioc_gq { 431 struct blkg_policy_data pd; 432 struct ioc *ioc; 433 434 /* 435 * A iocg can get its weight from two sources - an explicit 436 * per-device-cgroup configuration or the default weight of the 437 * cgroup. `cfg_weight` is the explicit per-device-cgroup 438 * configuration. `weight` is the effective considering both 439 * sources. 440 * 441 * When an idle cgroup becomes active its `active` goes from 0 to 442 * `weight`. `inuse` is the surplus adjusted active weight. 443 * `active` and `inuse` are used to calculate `hweight_active` and 444 * `hweight_inuse`. 445 * 446 * `last_inuse` remembers `inuse` while an iocg is idle to persist 447 * surplus adjustments. 448 */ 449 u32 cfg_weight; 450 u32 weight; 451 u32 active; 452 u32 inuse; 453 u32 last_inuse; 454 455 sector_t cursor; /* to detect randio */ 456 457 /* 458 * `vtime` is this iocg's vtime cursor which progresses as IOs are 459 * issued. If lagging behind device vtime, the delta represents 460 * the currently available IO budget. If runnning ahead, the 461 * overage. 462 * 463 * `vtime_done` is the same but progressed on completion rather 464 * than issue. The delta behind `vtime` represents the cost of 465 * currently in-flight IOs. 466 * 467 * `last_vtime` is used to remember `vtime` at the end of the last 468 * period to calculate utilization. 469 */ 470 atomic64_t vtime; 471 atomic64_t done_vtime; 472 atomic64_t abs_vdebt; 473 u64 last_vtime; 474 475 /* 476 * The period this iocg was last active in. Used for deactivation 477 * and invalidating `vtime`. 478 */ 479 atomic64_t active_period; 480 struct list_head active_list; 481 482 /* see __propagate_active_weight() and current_hweight() for details */ 483 u64 child_active_sum; 484 u64 child_inuse_sum; 485 int hweight_gen; 486 u32 hweight_active; 487 u32 hweight_inuse; 488 bool has_surplus; 489 490 struct wait_queue_head waitq; 491 struct hrtimer waitq_timer; 492 struct hrtimer delay_timer; 493 494 /* usage is recorded as fractions of HWEIGHT_WHOLE */ 495 int usage_idx; 496 u32 usages[NR_USAGE_SLOTS]; 497 498 /* this iocg's depth in the hierarchy and ancestors including self */ 499 int level; 500 struct ioc_gq *ancestors[]; 501 }; 502 503 /* per cgroup */ 504 struct ioc_cgrp { 505 struct blkcg_policy_data cpd; 506 unsigned int dfl_weight; 507 }; 508 509 struct ioc_now { 510 u64 now_ns; 511 u32 now; 512 u64 vnow; 513 u64 vrate; 514 }; 515 516 struct iocg_wait { 517 struct wait_queue_entry wait; 518 struct bio *bio; 519 u64 abs_cost; 520 bool committed; 521 }; 522 523 struct iocg_wake_ctx { 524 struct ioc_gq *iocg; 525 u32 hw_inuse; 526 s64 vbudget; 527 }; 528 529 static const struct ioc_params autop[] = { 530 [AUTOP_HDD] = { 531 .qos = { 532 [QOS_RLAT] = 250000, /* 250ms */ 533 [QOS_WLAT] = 250000, 534 [QOS_MIN] = VRATE_MIN_PPM, 535 [QOS_MAX] = VRATE_MAX_PPM, 536 }, 537 .i_lcoefs = { 538 [I_LCOEF_RBPS] = 174019176, 539 [I_LCOEF_RSEQIOPS] = 41708, 540 [I_LCOEF_RRANDIOPS] = 370, 541 [I_LCOEF_WBPS] = 178075866, 542 [I_LCOEF_WSEQIOPS] = 42705, 543 [I_LCOEF_WRANDIOPS] = 378, 544 }, 545 }, 546 [AUTOP_SSD_QD1] = { 547 .qos = { 548 [QOS_RLAT] = 25000, /* 25ms */ 549 [QOS_WLAT] = 25000, 550 [QOS_MIN] = VRATE_MIN_PPM, 551 [QOS_MAX] = VRATE_MAX_PPM, 552 }, 553 .i_lcoefs = { 554 [I_LCOEF_RBPS] = 245855193, 555 [I_LCOEF_RSEQIOPS] = 61575, 556 [I_LCOEF_RRANDIOPS] = 6946, 557 [I_LCOEF_WBPS] = 141365009, 558 [I_LCOEF_WSEQIOPS] = 33716, 559 [I_LCOEF_WRANDIOPS] = 26796, 560 }, 561 }, 562 [AUTOP_SSD_DFL] = { 563 .qos = { 564 [QOS_RLAT] = 25000, /* 25ms */ 565 [QOS_WLAT] = 25000, 566 [QOS_MIN] = VRATE_MIN_PPM, 567 [QOS_MAX] = VRATE_MAX_PPM, 568 }, 569 .i_lcoefs = { 570 [I_LCOEF_RBPS] = 488636629, 571 [I_LCOEF_RSEQIOPS] = 8932, 572 [I_LCOEF_RRANDIOPS] = 8518, 573 [I_LCOEF_WBPS] = 427891549, 574 [I_LCOEF_WSEQIOPS] = 28755, 575 [I_LCOEF_WRANDIOPS] = 21940, 576 }, 577 .too_fast_vrate_pct = 500, 578 }, 579 [AUTOP_SSD_FAST] = { 580 .qos = { 581 [QOS_RLAT] = 5000, /* 5ms */ 582 [QOS_WLAT] = 5000, 583 [QOS_MIN] = VRATE_MIN_PPM, 584 [QOS_MAX] = VRATE_MAX_PPM, 585 }, 586 .i_lcoefs = { 587 [I_LCOEF_RBPS] = 3102524156LLU, 588 [I_LCOEF_RSEQIOPS] = 724816, 589 [I_LCOEF_RRANDIOPS] = 778122, 590 [I_LCOEF_WBPS] = 1742780862LLU, 591 [I_LCOEF_WSEQIOPS] = 425702, 592 [I_LCOEF_WRANDIOPS] = 443193, 593 }, 594 .too_slow_vrate_pct = 10, 595 }, 596 }; 597 598 /* 599 * vrate adjust percentages indexed by ioc->busy_level. We adjust up on 600 * vtime credit shortage and down on device saturation. 601 */ 602 static u32 vrate_adj_pct[] = 603 { 0, 0, 0, 0, 604 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 605 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 606 4, 4, 4, 4, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 16 }; 607 608 static struct blkcg_policy blkcg_policy_iocost; 609 610 /* accessors and helpers */ 611 static struct ioc *rqos_to_ioc(struct rq_qos *rqos) 612 { 613 return container_of(rqos, struct ioc, rqos); 614 } 615 616 static struct ioc *q_to_ioc(struct request_queue *q) 617 { 618 return rqos_to_ioc(rq_qos_id(q, RQ_QOS_COST)); 619 } 620 621 static const char *q_name(struct request_queue *q) 622 { 623 if (test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags)) 624 return kobject_name(q->kobj.parent); 625 else 626 return "<unknown>"; 627 } 628 629 static const char __maybe_unused *ioc_name(struct ioc *ioc) 630 { 631 return q_name(ioc->rqos.q); 632 } 633 634 static struct ioc_gq *pd_to_iocg(struct blkg_policy_data *pd) 635 { 636 return pd ? container_of(pd, struct ioc_gq, pd) : NULL; 637 } 638 639 static struct ioc_gq *blkg_to_iocg(struct blkcg_gq *blkg) 640 { 641 return pd_to_iocg(blkg_to_pd(blkg, &blkcg_policy_iocost)); 642 } 643 644 static struct blkcg_gq *iocg_to_blkg(struct ioc_gq *iocg) 645 { 646 return pd_to_blkg(&iocg->pd); 647 } 648 649 static struct ioc_cgrp *blkcg_to_iocc(struct blkcg *blkcg) 650 { 651 return container_of(blkcg_to_cpd(blkcg, &blkcg_policy_iocost), 652 struct ioc_cgrp, cpd); 653 } 654 655 /* 656 * Scale @abs_cost to the inverse of @hw_inuse. The lower the hierarchical 657 * weight, the more expensive each IO. Must round up. 658 */ 659 static u64 abs_cost_to_cost(u64 abs_cost, u32 hw_inuse) 660 { 661 return DIV64_U64_ROUND_UP(abs_cost * HWEIGHT_WHOLE, hw_inuse); 662 } 663 664 /* 665 * The inverse of abs_cost_to_cost(). Must round up. 666 */ 667 static u64 cost_to_abs_cost(u64 cost, u32 hw_inuse) 668 { 669 return DIV64_U64_ROUND_UP(cost * hw_inuse, HWEIGHT_WHOLE); 670 } 671 672 static void iocg_commit_bio(struct ioc_gq *iocg, struct bio *bio, u64 cost) 673 { 674 bio->bi_iocost_cost = cost; 675 atomic64_add(cost, &iocg->vtime); 676 } 677 678 #define CREATE_TRACE_POINTS 679 #include <trace/events/iocost.h> 680 681 /* latency Qos params changed, update period_us and all the dependent params */ 682 static void ioc_refresh_period_us(struct ioc *ioc) 683 { 684 u32 ppm, lat, multi, period_us; 685 686 lockdep_assert_held(&ioc->lock); 687 688 /* pick the higher latency target */ 689 if (ioc->params.qos[QOS_RLAT] >= ioc->params.qos[QOS_WLAT]) { 690 ppm = ioc->params.qos[QOS_RPPM]; 691 lat = ioc->params.qos[QOS_RLAT]; 692 } else { 693 ppm = ioc->params.qos[QOS_WPPM]; 694 lat = ioc->params.qos[QOS_WLAT]; 695 } 696 697 /* 698 * We want the period to be long enough to contain a healthy number 699 * of IOs while short enough for granular control. Define it as a 700 * multiple of the latency target. Ideally, the multiplier should 701 * be scaled according to the percentile so that it would nominally 702 * contain a certain number of requests. Let's be simpler and 703 * scale it linearly so that it's 2x >= pct(90) and 10x at pct(50). 704 */ 705 if (ppm) 706 multi = max_t(u32, (MILLION - ppm) / 50000, 2); 707 else 708 multi = 2; 709 period_us = multi * lat; 710 period_us = clamp_t(u32, period_us, MIN_PERIOD, MAX_PERIOD); 711 712 /* calculate dependent params */ 713 ioc->period_us = period_us; 714 ioc->margin_us = period_us * MARGIN_PCT / 100; 715 ioc->inuse_margin_vtime = DIV64_U64_ROUND_UP( 716 period_us * VTIME_PER_USEC * INUSE_MARGIN_PCT, 100); 717 } 718 719 static int ioc_autop_idx(struct ioc *ioc) 720 { 721 int idx = ioc->autop_idx; 722 const struct ioc_params *p = &autop[idx]; 723 u32 vrate_pct; 724 u64 now_ns; 725 726 /* rotational? */ 727 if (!blk_queue_nonrot(ioc->rqos.q)) 728 return AUTOP_HDD; 729 730 /* handle SATA SSDs w/ broken NCQ */ 731 if (blk_queue_depth(ioc->rqos.q) == 1) 732 return AUTOP_SSD_QD1; 733 734 /* use one of the normal ssd sets */ 735 if (idx < AUTOP_SSD_DFL) 736 return AUTOP_SSD_DFL; 737 738 /* if user is overriding anything, maintain what was there */ 739 if (ioc->user_qos_params || ioc->user_cost_model) 740 return idx; 741 742 /* step up/down based on the vrate */ 743 vrate_pct = div64_u64(atomic64_read(&ioc->vtime_rate) * 100, 744 VTIME_PER_USEC); 745 now_ns = ktime_get_ns(); 746 747 if (p->too_fast_vrate_pct && p->too_fast_vrate_pct <= vrate_pct) { 748 if (!ioc->autop_too_fast_at) 749 ioc->autop_too_fast_at = now_ns; 750 if (now_ns - ioc->autop_too_fast_at >= AUTOP_CYCLE_NSEC) 751 return idx + 1; 752 } else { 753 ioc->autop_too_fast_at = 0; 754 } 755 756 if (p->too_slow_vrate_pct && p->too_slow_vrate_pct >= vrate_pct) { 757 if (!ioc->autop_too_slow_at) 758 ioc->autop_too_slow_at = now_ns; 759 if (now_ns - ioc->autop_too_slow_at >= AUTOP_CYCLE_NSEC) 760 return idx - 1; 761 } else { 762 ioc->autop_too_slow_at = 0; 763 } 764 765 return idx; 766 } 767 768 /* 769 * Take the followings as input 770 * 771 * @bps maximum sequential throughput 772 * @seqiops maximum sequential 4k iops 773 * @randiops maximum random 4k iops 774 * 775 * and calculate the linear model cost coefficients. 776 * 777 * *@page per-page cost 1s / (@bps / 4096) 778 * *@seqio base cost of a seq IO max((1s / @seqiops) - *@page, 0) 779 * @randiops base cost of a rand IO max((1s / @randiops) - *@page, 0) 780 */ 781 static void calc_lcoefs(u64 bps, u64 seqiops, u64 randiops, 782 u64 *page, u64 *seqio, u64 *randio) 783 { 784 u64 v; 785 786 *page = *seqio = *randio = 0; 787 788 if (bps) 789 *page = DIV64_U64_ROUND_UP(VTIME_PER_SEC, 790 DIV_ROUND_UP_ULL(bps, IOC_PAGE_SIZE)); 791 792 if (seqiops) { 793 v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, seqiops); 794 if (v > *page) 795 *seqio = v - *page; 796 } 797 798 if (randiops) { 799 v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, randiops); 800 if (v > *page) 801 *randio = v - *page; 802 } 803 } 804 805 static void ioc_refresh_lcoefs(struct ioc *ioc) 806 { 807 u64 *u = ioc->params.i_lcoefs; 808 u64 *c = ioc->params.lcoefs; 809 810 calc_lcoefs(u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS], 811 &c[LCOEF_RPAGE], &c[LCOEF_RSEQIO], &c[LCOEF_RRANDIO]); 812 calc_lcoefs(u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS], 813 &c[LCOEF_WPAGE], &c[LCOEF_WSEQIO], &c[LCOEF_WRANDIO]); 814 } 815 816 static bool ioc_refresh_params(struct ioc *ioc, bool force) 817 { 818 const struct ioc_params *p; 819 int idx; 820 821 lockdep_assert_held(&ioc->lock); 822 823 idx = ioc_autop_idx(ioc); 824 p = &autop[idx]; 825 826 if (idx == ioc->autop_idx && !force) 827 return false; 828 829 if (idx != ioc->autop_idx) 830 atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC); 831 832 ioc->autop_idx = idx; 833 ioc->autop_too_fast_at = 0; 834 ioc->autop_too_slow_at = 0; 835 836 if (!ioc->user_qos_params) 837 memcpy(ioc->params.qos, p->qos, sizeof(p->qos)); 838 if (!ioc->user_cost_model) 839 memcpy(ioc->params.i_lcoefs, p->i_lcoefs, sizeof(p->i_lcoefs)); 840 841 ioc_refresh_period_us(ioc); 842 ioc_refresh_lcoefs(ioc); 843 844 ioc->vrate_min = DIV64_U64_ROUND_UP((u64)ioc->params.qos[QOS_MIN] * 845 VTIME_PER_USEC, MILLION); 846 ioc->vrate_max = div64_u64((u64)ioc->params.qos[QOS_MAX] * 847 VTIME_PER_USEC, MILLION); 848 849 return true; 850 } 851 852 /* take a snapshot of the current [v]time and vrate */ 853 static void ioc_now(struct ioc *ioc, struct ioc_now *now) 854 { 855 unsigned seq; 856 857 now->now_ns = ktime_get(); 858 now->now = ktime_to_us(now->now_ns); 859 now->vrate = atomic64_read(&ioc->vtime_rate); 860 861 /* 862 * The current vtime is 863 * 864 * vtime at period start + (wallclock time since the start) * vrate 865 * 866 * As a consistent snapshot of `period_at_vtime` and `period_at` is 867 * needed, they're seqcount protected. 868 */ 869 do { 870 seq = read_seqcount_begin(&ioc->period_seqcount); 871 now->vnow = ioc->period_at_vtime + 872 (now->now - ioc->period_at) * now->vrate; 873 } while (read_seqcount_retry(&ioc->period_seqcount, seq)); 874 } 875 876 static void ioc_start_period(struct ioc *ioc, struct ioc_now *now) 877 { 878 lockdep_assert_held(&ioc->lock); 879 WARN_ON_ONCE(ioc->running != IOC_RUNNING); 880 881 write_seqcount_begin(&ioc->period_seqcount); 882 ioc->period_at = now->now; 883 ioc->period_at_vtime = now->vnow; 884 write_seqcount_end(&ioc->period_seqcount); 885 886 ioc->timer.expires = jiffies + usecs_to_jiffies(ioc->period_us); 887 add_timer(&ioc->timer); 888 } 889 890 /* 891 * Update @iocg's `active` and `inuse` to @active and @inuse, update level 892 * weight sums and propagate upwards accordingly. 893 */ 894 static void __propagate_active_weight(struct ioc_gq *iocg, u32 active, u32 inuse) 895 { 896 struct ioc *ioc = iocg->ioc; 897 int lvl; 898 899 lockdep_assert_held(&ioc->lock); 900 901 inuse = min(active, inuse); 902 903 for (lvl = iocg->level - 1; lvl >= 0; lvl--) { 904 struct ioc_gq *parent = iocg->ancestors[lvl]; 905 struct ioc_gq *child = iocg->ancestors[lvl + 1]; 906 u32 parent_active = 0, parent_inuse = 0; 907 908 /* update the level sums */ 909 parent->child_active_sum += (s32)(active - child->active); 910 parent->child_inuse_sum += (s32)(inuse - child->inuse); 911 /* apply the udpates */ 912 child->active = active; 913 child->inuse = inuse; 914 915 /* 916 * The delta between inuse and active sums indicates that 917 * that much of weight is being given away. Parent's inuse 918 * and active should reflect the ratio. 919 */ 920 if (parent->child_active_sum) { 921 parent_active = parent->weight; 922 parent_inuse = DIV64_U64_ROUND_UP( 923 parent_active * parent->child_inuse_sum, 924 parent->child_active_sum); 925 } 926 927 /* do we need to keep walking up? */ 928 if (parent_active == parent->active && 929 parent_inuse == parent->inuse) 930 break; 931 932 active = parent_active; 933 inuse = parent_inuse; 934 } 935 936 ioc->weights_updated = true; 937 } 938 939 static void commit_active_weights(struct ioc *ioc) 940 { 941 lockdep_assert_held(&ioc->lock); 942 943 if (ioc->weights_updated) { 944 /* paired with rmb in current_hweight(), see there */ 945 smp_wmb(); 946 atomic_inc(&ioc->hweight_gen); 947 ioc->weights_updated = false; 948 } 949 } 950 951 static void propagate_active_weight(struct ioc_gq *iocg, u32 active, u32 inuse) 952 { 953 __propagate_active_weight(iocg, active, inuse); 954 commit_active_weights(iocg->ioc); 955 } 956 957 static void current_hweight(struct ioc_gq *iocg, u32 *hw_activep, u32 *hw_inusep) 958 { 959 struct ioc *ioc = iocg->ioc; 960 int lvl; 961 u32 hwa, hwi; 962 int ioc_gen; 963 964 /* hot path - if uptodate, use cached */ 965 ioc_gen = atomic_read(&ioc->hweight_gen); 966 if (ioc_gen == iocg->hweight_gen) 967 goto out; 968 969 /* 970 * Paired with wmb in commit_active_weights(). If we saw the 971 * updated hweight_gen, all the weight updates from 972 * __propagate_active_weight() are visible too. 973 * 974 * We can race with weight updates during calculation and get it 975 * wrong. However, hweight_gen would have changed and a future 976 * reader will recalculate and we're guaranteed to discard the 977 * wrong result soon. 978 */ 979 smp_rmb(); 980 981 hwa = hwi = HWEIGHT_WHOLE; 982 for (lvl = 0; lvl <= iocg->level - 1; lvl++) { 983 struct ioc_gq *parent = iocg->ancestors[lvl]; 984 struct ioc_gq *child = iocg->ancestors[lvl + 1]; 985 u32 active_sum = READ_ONCE(parent->child_active_sum); 986 u32 inuse_sum = READ_ONCE(parent->child_inuse_sum); 987 u32 active = READ_ONCE(child->active); 988 u32 inuse = READ_ONCE(child->inuse); 989 990 /* we can race with deactivations and either may read as zero */ 991 if (!active_sum || !inuse_sum) 992 continue; 993 994 active_sum = max(active, active_sum); 995 hwa = hwa * active / active_sum; /* max 16bits * 10000 */ 996 997 inuse_sum = max(inuse, inuse_sum); 998 hwi = hwi * inuse / inuse_sum; /* max 16bits * 10000 */ 999 } 1000 1001 iocg->hweight_active = max_t(u32, hwa, 1); 1002 iocg->hweight_inuse = max_t(u32, hwi, 1); 1003 iocg->hweight_gen = ioc_gen; 1004 out: 1005 if (hw_activep) 1006 *hw_activep = iocg->hweight_active; 1007 if (hw_inusep) 1008 *hw_inusep = iocg->hweight_inuse; 1009 } 1010 1011 static void weight_updated(struct ioc_gq *iocg) 1012 { 1013 struct ioc *ioc = iocg->ioc; 1014 struct blkcg_gq *blkg = iocg_to_blkg(iocg); 1015 struct ioc_cgrp *iocc = blkcg_to_iocc(blkg->blkcg); 1016 u32 weight; 1017 1018 lockdep_assert_held(&ioc->lock); 1019 1020 weight = iocg->cfg_weight ?: iocc->dfl_weight; 1021 if (weight != iocg->weight && iocg->active) 1022 propagate_active_weight(iocg, weight, 1023 DIV64_U64_ROUND_UP(iocg->inuse * weight, iocg->weight)); 1024 iocg->weight = weight; 1025 } 1026 1027 static bool iocg_activate(struct ioc_gq *iocg, struct ioc_now *now) 1028 { 1029 struct ioc *ioc = iocg->ioc; 1030 u64 last_period, cur_period, max_period_delta; 1031 u64 vtime, vmargin, vmin; 1032 int i; 1033 1034 /* 1035 * If seem to be already active, just update the stamp to tell the 1036 * timer that we're still active. We don't mind occassional races. 1037 */ 1038 if (!list_empty(&iocg->active_list)) { 1039 ioc_now(ioc, now); 1040 cur_period = atomic64_read(&ioc->cur_period); 1041 if (atomic64_read(&iocg->active_period) != cur_period) 1042 atomic64_set(&iocg->active_period, cur_period); 1043 return true; 1044 } 1045 1046 /* racy check on internal node IOs, treat as root level IOs */ 1047 if (iocg->child_active_sum) 1048 return false; 1049 1050 spin_lock_irq(&ioc->lock); 1051 1052 ioc_now(ioc, now); 1053 1054 /* update period */ 1055 cur_period = atomic64_read(&ioc->cur_period); 1056 last_period = atomic64_read(&iocg->active_period); 1057 atomic64_set(&iocg->active_period, cur_period); 1058 1059 /* already activated or breaking leaf-only constraint? */ 1060 if (!list_empty(&iocg->active_list)) 1061 goto succeed_unlock; 1062 for (i = iocg->level - 1; i > 0; i--) 1063 if (!list_empty(&iocg->ancestors[i]->active_list)) 1064 goto fail_unlock; 1065 1066 if (iocg->child_active_sum) 1067 goto fail_unlock; 1068 1069 /* 1070 * vtime may wrap when vrate is raised substantially due to 1071 * underestimated IO costs. Look at the period and ignore its 1072 * vtime if the iocg has been idle for too long. Also, cap the 1073 * budget it can start with to the margin. 1074 */ 1075 max_period_delta = DIV64_U64_ROUND_UP(VTIME_VALID_DUR, ioc->period_us); 1076 vtime = atomic64_read(&iocg->vtime); 1077 vmargin = ioc->margin_us * now->vrate; 1078 vmin = now->vnow - vmargin; 1079 1080 if (last_period + max_period_delta < cur_period || 1081 time_before64(vtime, vmin)) { 1082 atomic64_add(vmin - vtime, &iocg->vtime); 1083 atomic64_add(vmin - vtime, &iocg->done_vtime); 1084 vtime = vmin; 1085 } 1086 1087 /* 1088 * Activate, propagate weight and start period timer if not 1089 * running. Reset hweight_gen to avoid accidental match from 1090 * wrapping. 1091 */ 1092 iocg->hweight_gen = atomic_read(&ioc->hweight_gen) - 1; 1093 list_add(&iocg->active_list, &ioc->active_iocgs); 1094 propagate_active_weight(iocg, iocg->weight, 1095 iocg->last_inuse ?: iocg->weight); 1096 1097 TRACE_IOCG_PATH(iocg_activate, iocg, now, 1098 last_period, cur_period, vtime); 1099 1100 iocg->last_vtime = vtime; 1101 1102 if (ioc->running == IOC_IDLE) { 1103 ioc->running = IOC_RUNNING; 1104 ioc_start_period(ioc, now); 1105 } 1106 1107 succeed_unlock: 1108 spin_unlock_irq(&ioc->lock); 1109 return true; 1110 1111 fail_unlock: 1112 spin_unlock_irq(&ioc->lock); 1113 return false; 1114 } 1115 1116 static int iocg_wake_fn(struct wait_queue_entry *wq_entry, unsigned mode, 1117 int flags, void *key) 1118 { 1119 struct iocg_wait *wait = container_of(wq_entry, struct iocg_wait, wait); 1120 struct iocg_wake_ctx *ctx = (struct iocg_wake_ctx *)key; 1121 u64 cost = abs_cost_to_cost(wait->abs_cost, ctx->hw_inuse); 1122 1123 ctx->vbudget -= cost; 1124 1125 if (ctx->vbudget < 0) 1126 return -1; 1127 1128 iocg_commit_bio(ctx->iocg, wait->bio, cost); 1129 1130 /* 1131 * autoremove_wake_function() removes the wait entry only when it 1132 * actually changed the task state. We want the wait always 1133 * removed. Remove explicitly and use default_wake_function(). 1134 */ 1135 list_del_init(&wq_entry->entry); 1136 wait->committed = true; 1137 1138 default_wake_function(wq_entry, mode, flags, key); 1139 return 0; 1140 } 1141 1142 static void iocg_kick_waitq(struct ioc_gq *iocg, struct ioc_now *now) 1143 { 1144 struct ioc *ioc = iocg->ioc; 1145 struct iocg_wake_ctx ctx = { .iocg = iocg }; 1146 u64 margin_ns = (u64)(ioc->period_us * 1147 WAITQ_TIMER_MARGIN_PCT / 100) * NSEC_PER_USEC; 1148 u64 abs_vdebt, vdebt, vshortage, expires, oexpires; 1149 s64 vbudget; 1150 u32 hw_inuse; 1151 1152 lockdep_assert_held(&iocg->waitq.lock); 1153 1154 current_hweight(iocg, NULL, &hw_inuse); 1155 vbudget = now->vnow - atomic64_read(&iocg->vtime); 1156 1157 /* pay off debt */ 1158 abs_vdebt = atomic64_read(&iocg->abs_vdebt); 1159 vdebt = abs_cost_to_cost(abs_vdebt, hw_inuse); 1160 if (vdebt && vbudget > 0) { 1161 u64 delta = min_t(u64, vbudget, vdebt); 1162 u64 abs_delta = min(cost_to_abs_cost(delta, hw_inuse), 1163 abs_vdebt); 1164 1165 atomic64_add(delta, &iocg->vtime); 1166 atomic64_add(delta, &iocg->done_vtime); 1167 atomic64_sub(abs_delta, &iocg->abs_vdebt); 1168 if (WARN_ON_ONCE(atomic64_read(&iocg->abs_vdebt) < 0)) 1169 atomic64_set(&iocg->abs_vdebt, 0); 1170 } 1171 1172 /* 1173 * Wake up the ones which are due and see how much vtime we'll need 1174 * for the next one. 1175 */ 1176 ctx.hw_inuse = hw_inuse; 1177 ctx.vbudget = vbudget - vdebt; 1178 __wake_up_locked_key(&iocg->waitq, TASK_NORMAL, &ctx); 1179 if (!waitqueue_active(&iocg->waitq)) 1180 return; 1181 if (WARN_ON_ONCE(ctx.vbudget >= 0)) 1182 return; 1183 1184 /* determine next wakeup, add a quarter margin to guarantee chunking */ 1185 vshortage = -ctx.vbudget; 1186 expires = now->now_ns + 1187 DIV64_U64_ROUND_UP(vshortage, now->vrate) * NSEC_PER_USEC; 1188 expires += margin_ns / 4; 1189 1190 /* if already active and close enough, don't bother */ 1191 oexpires = ktime_to_ns(hrtimer_get_softexpires(&iocg->waitq_timer)); 1192 if (hrtimer_is_queued(&iocg->waitq_timer) && 1193 abs(oexpires - expires) <= margin_ns / 4) 1194 return; 1195 1196 hrtimer_start_range_ns(&iocg->waitq_timer, ns_to_ktime(expires), 1197 margin_ns / 4, HRTIMER_MODE_ABS); 1198 } 1199 1200 static enum hrtimer_restart iocg_waitq_timer_fn(struct hrtimer *timer) 1201 { 1202 struct ioc_gq *iocg = container_of(timer, struct ioc_gq, waitq_timer); 1203 struct ioc_now now; 1204 unsigned long flags; 1205 1206 ioc_now(iocg->ioc, &now); 1207 1208 spin_lock_irqsave(&iocg->waitq.lock, flags); 1209 iocg_kick_waitq(iocg, &now); 1210 spin_unlock_irqrestore(&iocg->waitq.lock, flags); 1211 1212 return HRTIMER_NORESTART; 1213 } 1214 1215 static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now, u64 cost) 1216 { 1217 struct ioc *ioc = iocg->ioc; 1218 struct blkcg_gq *blkg = iocg_to_blkg(iocg); 1219 u64 vtime = atomic64_read(&iocg->vtime); 1220 u64 vmargin = ioc->margin_us * now->vrate; 1221 u64 margin_ns = ioc->margin_us * NSEC_PER_USEC; 1222 u64 expires, oexpires; 1223 u32 hw_inuse; 1224 1225 /* debt-adjust vtime */ 1226 current_hweight(iocg, NULL, &hw_inuse); 1227 vtime += abs_cost_to_cost(atomic64_read(&iocg->abs_vdebt), hw_inuse); 1228 1229 /* clear or maintain depending on the overage */ 1230 if (time_before_eq64(vtime, now->vnow)) { 1231 blkcg_clear_delay(blkg); 1232 return false; 1233 } 1234 if (!atomic_read(&blkg->use_delay) && 1235 time_before_eq64(vtime, now->vnow + vmargin)) 1236 return false; 1237 1238 /* use delay */ 1239 if (cost) { 1240 u64 cost_ns = DIV64_U64_ROUND_UP(cost * NSEC_PER_USEC, 1241 now->vrate); 1242 blkcg_add_delay(blkg, now->now_ns, cost_ns); 1243 } 1244 blkcg_use_delay(blkg); 1245 1246 expires = now->now_ns + DIV64_U64_ROUND_UP(vtime - now->vnow, 1247 now->vrate) * NSEC_PER_USEC; 1248 1249 /* if already active and close enough, don't bother */ 1250 oexpires = ktime_to_ns(hrtimer_get_softexpires(&iocg->delay_timer)); 1251 if (hrtimer_is_queued(&iocg->delay_timer) && 1252 abs(oexpires - expires) <= margin_ns / 4) 1253 return true; 1254 1255 hrtimer_start_range_ns(&iocg->delay_timer, ns_to_ktime(expires), 1256 margin_ns / 4, HRTIMER_MODE_ABS); 1257 return true; 1258 } 1259 1260 static enum hrtimer_restart iocg_delay_timer_fn(struct hrtimer *timer) 1261 { 1262 struct ioc_gq *iocg = container_of(timer, struct ioc_gq, delay_timer); 1263 struct ioc_now now; 1264 1265 ioc_now(iocg->ioc, &now); 1266 iocg_kick_delay(iocg, &now, 0); 1267 1268 return HRTIMER_NORESTART; 1269 } 1270 1271 static void ioc_lat_stat(struct ioc *ioc, u32 *missed_ppm_ar, u32 *rq_wait_pct_p) 1272 { 1273 u32 nr_met[2] = { }; 1274 u32 nr_missed[2] = { }; 1275 u64 rq_wait_ns = 0; 1276 int cpu, rw; 1277 1278 for_each_online_cpu(cpu) { 1279 struct ioc_pcpu_stat *stat = per_cpu_ptr(ioc->pcpu_stat, cpu); 1280 u64 this_rq_wait_ns; 1281 1282 for (rw = READ; rw <= WRITE; rw++) { 1283 u32 this_met = READ_ONCE(stat->missed[rw].nr_met); 1284 u32 this_missed = READ_ONCE(stat->missed[rw].nr_missed); 1285 1286 nr_met[rw] += this_met - stat->missed[rw].last_met; 1287 nr_missed[rw] += this_missed - stat->missed[rw].last_missed; 1288 stat->missed[rw].last_met = this_met; 1289 stat->missed[rw].last_missed = this_missed; 1290 } 1291 1292 this_rq_wait_ns = READ_ONCE(stat->rq_wait_ns); 1293 rq_wait_ns += this_rq_wait_ns - stat->last_rq_wait_ns; 1294 stat->last_rq_wait_ns = this_rq_wait_ns; 1295 } 1296 1297 for (rw = READ; rw <= WRITE; rw++) { 1298 if (nr_met[rw] + nr_missed[rw]) 1299 missed_ppm_ar[rw] = 1300 DIV64_U64_ROUND_UP((u64)nr_missed[rw] * MILLION, 1301 nr_met[rw] + nr_missed[rw]); 1302 else 1303 missed_ppm_ar[rw] = 0; 1304 } 1305 1306 *rq_wait_pct_p = div64_u64(rq_wait_ns * 100, 1307 ioc->period_us * NSEC_PER_USEC); 1308 } 1309 1310 /* was iocg idle this period? */ 1311 static bool iocg_is_idle(struct ioc_gq *iocg) 1312 { 1313 struct ioc *ioc = iocg->ioc; 1314 1315 /* did something get issued this period? */ 1316 if (atomic64_read(&iocg->active_period) == 1317 atomic64_read(&ioc->cur_period)) 1318 return false; 1319 1320 /* is something in flight? */ 1321 if (atomic64_read(&iocg->done_vtime) != atomic64_read(&iocg->vtime)) 1322 return false; 1323 1324 return true; 1325 } 1326 1327 /* returns usage with margin added if surplus is large enough */ 1328 static u32 surplus_adjusted_hweight_inuse(u32 usage, u32 hw_inuse) 1329 { 1330 /* add margin */ 1331 usage = DIV_ROUND_UP(usage * SURPLUS_SCALE_PCT, 100); 1332 usage += SURPLUS_SCALE_ABS; 1333 1334 /* don't bother if the surplus is too small */ 1335 if (usage + SURPLUS_MIN_ADJ_DELTA > hw_inuse) 1336 return 0; 1337 1338 return usage; 1339 } 1340 1341 static void ioc_timer_fn(struct timer_list *timer) 1342 { 1343 struct ioc *ioc = container_of(timer, struct ioc, timer); 1344 struct ioc_gq *iocg, *tiocg; 1345 struct ioc_now now; 1346 int nr_surpluses = 0, nr_shortages = 0, nr_lagging = 0; 1347 u32 ppm_rthr = MILLION - ioc->params.qos[QOS_RPPM]; 1348 u32 ppm_wthr = MILLION - ioc->params.qos[QOS_WPPM]; 1349 u32 missed_ppm[2], rq_wait_pct; 1350 u64 period_vtime; 1351 int prev_busy_level, i; 1352 1353 /* how were the latencies during the period? */ 1354 ioc_lat_stat(ioc, missed_ppm, &rq_wait_pct); 1355 1356 /* take care of active iocgs */ 1357 spin_lock_irq(&ioc->lock); 1358 1359 ioc_now(ioc, &now); 1360 1361 period_vtime = now.vnow - ioc->period_at_vtime; 1362 if (WARN_ON_ONCE(!period_vtime)) { 1363 spin_unlock_irq(&ioc->lock); 1364 return; 1365 } 1366 1367 /* 1368 * Waiters determine the sleep durations based on the vrate they 1369 * saw at the time of sleep. If vrate has increased, some waiters 1370 * could be sleeping for too long. Wake up tardy waiters which 1371 * should have woken up in the last period and expire idle iocgs. 1372 */ 1373 list_for_each_entry_safe(iocg, tiocg, &ioc->active_iocgs, active_list) { 1374 if (!waitqueue_active(&iocg->waitq) && 1375 !atomic64_read(&iocg->abs_vdebt) && !iocg_is_idle(iocg)) 1376 continue; 1377 1378 spin_lock(&iocg->waitq.lock); 1379 1380 if (waitqueue_active(&iocg->waitq) || 1381 atomic64_read(&iocg->abs_vdebt)) { 1382 /* might be oversleeping vtime / hweight changes, kick */ 1383 iocg_kick_waitq(iocg, &now); 1384 iocg_kick_delay(iocg, &now, 0); 1385 } else if (iocg_is_idle(iocg)) { 1386 /* no waiter and idle, deactivate */ 1387 iocg->last_inuse = iocg->inuse; 1388 __propagate_active_weight(iocg, 0, 0); 1389 list_del_init(&iocg->active_list); 1390 } 1391 1392 spin_unlock(&iocg->waitq.lock); 1393 } 1394 commit_active_weights(ioc); 1395 1396 /* calc usages and see whether some weights need to be moved around */ 1397 list_for_each_entry(iocg, &ioc->active_iocgs, active_list) { 1398 u64 vdone, vtime, vusage, vmargin, vmin; 1399 u32 hw_active, hw_inuse, usage; 1400 1401 /* 1402 * Collect unused and wind vtime closer to vnow to prevent 1403 * iocgs from accumulating a large amount of budget. 1404 */ 1405 vdone = atomic64_read(&iocg->done_vtime); 1406 vtime = atomic64_read(&iocg->vtime); 1407 current_hweight(iocg, &hw_active, &hw_inuse); 1408 1409 /* 1410 * Latency QoS detection doesn't account for IOs which are 1411 * in-flight for longer than a period. Detect them by 1412 * comparing vdone against period start. If lagging behind 1413 * IOs from past periods, don't increase vrate. 1414 */ 1415 if ((ppm_rthr != MILLION || ppm_wthr != MILLION) && 1416 !atomic_read(&iocg_to_blkg(iocg)->use_delay) && 1417 time_after64(vtime, vdone) && 1418 time_after64(vtime, now.vnow - 1419 MAX_LAGGING_PERIODS * period_vtime) && 1420 time_before64(vdone, now.vnow - period_vtime)) 1421 nr_lagging++; 1422 1423 if (waitqueue_active(&iocg->waitq)) 1424 vusage = now.vnow - iocg->last_vtime; 1425 else if (time_before64(iocg->last_vtime, vtime)) 1426 vusage = vtime - iocg->last_vtime; 1427 else 1428 vusage = 0; 1429 1430 iocg->last_vtime += vusage; 1431 /* 1432 * Factor in in-flight vtime into vusage to avoid 1433 * high-latency completions appearing as idle. This should 1434 * be done after the above ->last_time adjustment. 1435 */ 1436 vusage = max(vusage, vtime - vdone); 1437 1438 /* calculate hweight based usage ratio and record */ 1439 if (vusage) { 1440 usage = DIV64_U64_ROUND_UP(vusage * hw_inuse, 1441 period_vtime); 1442 iocg->usage_idx = (iocg->usage_idx + 1) % NR_USAGE_SLOTS; 1443 iocg->usages[iocg->usage_idx] = usage; 1444 } else { 1445 usage = 0; 1446 } 1447 1448 /* see whether there's surplus vtime */ 1449 vmargin = ioc->margin_us * now.vrate; 1450 vmin = now.vnow - vmargin; 1451 1452 iocg->has_surplus = false; 1453 1454 if (!waitqueue_active(&iocg->waitq) && 1455 time_before64(vtime, vmin)) { 1456 u64 delta = vmin - vtime; 1457 1458 /* throw away surplus vtime */ 1459 atomic64_add(delta, &iocg->vtime); 1460 atomic64_add(delta, &iocg->done_vtime); 1461 iocg->last_vtime += delta; 1462 /* if usage is sufficiently low, maybe it can donate */ 1463 if (surplus_adjusted_hweight_inuse(usage, hw_inuse)) { 1464 iocg->has_surplus = true; 1465 nr_surpluses++; 1466 } 1467 } else if (hw_inuse < hw_active) { 1468 u32 new_hwi, new_inuse; 1469 1470 /* was donating but might need to take back some */ 1471 if (waitqueue_active(&iocg->waitq)) { 1472 new_hwi = hw_active; 1473 } else { 1474 new_hwi = max(hw_inuse, 1475 usage * SURPLUS_SCALE_PCT / 100 + 1476 SURPLUS_SCALE_ABS); 1477 } 1478 1479 new_inuse = div64_u64((u64)iocg->inuse * new_hwi, 1480 hw_inuse); 1481 new_inuse = clamp_t(u32, new_inuse, 1, iocg->active); 1482 1483 if (new_inuse > iocg->inuse) { 1484 TRACE_IOCG_PATH(inuse_takeback, iocg, &now, 1485 iocg->inuse, new_inuse, 1486 hw_inuse, new_hwi); 1487 __propagate_active_weight(iocg, iocg->weight, 1488 new_inuse); 1489 } 1490 } else { 1491 /* genuninely out of vtime */ 1492 nr_shortages++; 1493 } 1494 } 1495 1496 if (!nr_shortages || !nr_surpluses) 1497 goto skip_surplus_transfers; 1498 1499 /* there are both shortages and surpluses, transfer surpluses */ 1500 list_for_each_entry(iocg, &ioc->active_iocgs, active_list) { 1501 u32 usage, hw_active, hw_inuse, new_hwi, new_inuse; 1502 int nr_valid = 0; 1503 1504 if (!iocg->has_surplus) 1505 continue; 1506 1507 /* base the decision on max historical usage */ 1508 for (i = 0, usage = 0; i < NR_USAGE_SLOTS; i++) { 1509 if (iocg->usages[i]) { 1510 usage = max(usage, iocg->usages[i]); 1511 nr_valid++; 1512 } 1513 } 1514 if (nr_valid < MIN_VALID_USAGES) 1515 continue; 1516 1517 current_hweight(iocg, &hw_active, &hw_inuse); 1518 new_hwi = surplus_adjusted_hweight_inuse(usage, hw_inuse); 1519 if (!new_hwi) 1520 continue; 1521 1522 new_inuse = DIV64_U64_ROUND_UP((u64)iocg->inuse * new_hwi, 1523 hw_inuse); 1524 if (new_inuse < iocg->inuse) { 1525 TRACE_IOCG_PATH(inuse_giveaway, iocg, &now, 1526 iocg->inuse, new_inuse, 1527 hw_inuse, new_hwi); 1528 __propagate_active_weight(iocg, iocg->weight, new_inuse); 1529 } 1530 } 1531 skip_surplus_transfers: 1532 commit_active_weights(ioc); 1533 1534 /* 1535 * If q is getting clogged or we're missing too much, we're issuing 1536 * too much IO and should lower vtime rate. If we're not missing 1537 * and experiencing shortages but not surpluses, we're too stingy 1538 * and should increase vtime rate. 1539 */ 1540 prev_busy_level = ioc->busy_level; 1541 if (rq_wait_pct > RQ_WAIT_BUSY_PCT || 1542 missed_ppm[READ] > ppm_rthr || 1543 missed_ppm[WRITE] > ppm_wthr) { 1544 ioc->busy_level = max(ioc->busy_level, 0); 1545 ioc->busy_level++; 1546 } else if (rq_wait_pct <= RQ_WAIT_BUSY_PCT * UNBUSY_THR_PCT / 100 && 1547 missed_ppm[READ] <= ppm_rthr * UNBUSY_THR_PCT / 100 && 1548 missed_ppm[WRITE] <= ppm_wthr * UNBUSY_THR_PCT / 100) { 1549 /* take action iff there is contention */ 1550 if (nr_shortages && !nr_lagging) { 1551 ioc->busy_level = min(ioc->busy_level, 0); 1552 /* redistribute surpluses first */ 1553 if (!nr_surpluses) 1554 ioc->busy_level--; 1555 } 1556 } else { 1557 ioc->busy_level = 0; 1558 } 1559 1560 ioc->busy_level = clamp(ioc->busy_level, -1000, 1000); 1561 1562 if (ioc->busy_level > 0 || (ioc->busy_level < 0 && !nr_lagging)) { 1563 u64 vrate = atomic64_read(&ioc->vtime_rate); 1564 u64 vrate_min = ioc->vrate_min, vrate_max = ioc->vrate_max; 1565 1566 /* rq_wait signal is always reliable, ignore user vrate_min */ 1567 if (rq_wait_pct > RQ_WAIT_BUSY_PCT) 1568 vrate_min = VRATE_MIN; 1569 1570 /* 1571 * If vrate is out of bounds, apply clamp gradually as the 1572 * bounds can change abruptly. Otherwise, apply busy_level 1573 * based adjustment. 1574 */ 1575 if (vrate < vrate_min) { 1576 vrate = div64_u64(vrate * (100 + VRATE_CLAMP_ADJ_PCT), 1577 100); 1578 vrate = min(vrate, vrate_min); 1579 } else if (vrate > vrate_max) { 1580 vrate = div64_u64(vrate * (100 - VRATE_CLAMP_ADJ_PCT), 1581 100); 1582 vrate = max(vrate, vrate_max); 1583 } else { 1584 int idx = min_t(int, abs(ioc->busy_level), 1585 ARRAY_SIZE(vrate_adj_pct) - 1); 1586 u32 adj_pct = vrate_adj_pct[idx]; 1587 1588 if (ioc->busy_level > 0) 1589 adj_pct = 100 - adj_pct; 1590 else 1591 adj_pct = 100 + adj_pct; 1592 1593 vrate = clamp(DIV64_U64_ROUND_UP(vrate * adj_pct, 100), 1594 vrate_min, vrate_max); 1595 } 1596 1597 trace_iocost_ioc_vrate_adj(ioc, vrate, &missed_ppm, rq_wait_pct, 1598 nr_lagging, nr_shortages, 1599 nr_surpluses); 1600 1601 atomic64_set(&ioc->vtime_rate, vrate); 1602 ioc->inuse_margin_vtime = DIV64_U64_ROUND_UP( 1603 ioc->period_us * vrate * INUSE_MARGIN_PCT, 100); 1604 } else if (ioc->busy_level != prev_busy_level || nr_lagging) { 1605 trace_iocost_ioc_vrate_adj(ioc, atomic64_read(&ioc->vtime_rate), 1606 &missed_ppm, rq_wait_pct, nr_lagging, 1607 nr_shortages, nr_surpluses); 1608 } 1609 1610 ioc_refresh_params(ioc, false); 1611 1612 /* 1613 * This period is done. Move onto the next one. If nothing's 1614 * going on with the device, stop the timer. 1615 */ 1616 atomic64_inc(&ioc->cur_period); 1617 1618 if (ioc->running != IOC_STOP) { 1619 if (!list_empty(&ioc->active_iocgs)) { 1620 ioc_start_period(ioc, &now); 1621 } else { 1622 ioc->busy_level = 0; 1623 ioc->running = IOC_IDLE; 1624 } 1625 } 1626 1627 spin_unlock_irq(&ioc->lock); 1628 } 1629 1630 static void calc_vtime_cost_builtin(struct bio *bio, struct ioc_gq *iocg, 1631 bool is_merge, u64 *costp) 1632 { 1633 struct ioc *ioc = iocg->ioc; 1634 u64 coef_seqio, coef_randio, coef_page; 1635 u64 pages = max_t(u64, bio_sectors(bio) >> IOC_SECT_TO_PAGE_SHIFT, 1); 1636 u64 seek_pages = 0; 1637 u64 cost = 0; 1638 1639 switch (bio_op(bio)) { 1640 case REQ_OP_READ: 1641 coef_seqio = ioc->params.lcoefs[LCOEF_RSEQIO]; 1642 coef_randio = ioc->params.lcoefs[LCOEF_RRANDIO]; 1643 coef_page = ioc->params.lcoefs[LCOEF_RPAGE]; 1644 break; 1645 case REQ_OP_WRITE: 1646 coef_seqio = ioc->params.lcoefs[LCOEF_WSEQIO]; 1647 coef_randio = ioc->params.lcoefs[LCOEF_WRANDIO]; 1648 coef_page = ioc->params.lcoefs[LCOEF_WPAGE]; 1649 break; 1650 default: 1651 goto out; 1652 } 1653 1654 if (iocg->cursor) { 1655 seek_pages = abs(bio->bi_iter.bi_sector - iocg->cursor); 1656 seek_pages >>= IOC_SECT_TO_PAGE_SHIFT; 1657 } 1658 1659 if (!is_merge) { 1660 if (seek_pages > LCOEF_RANDIO_PAGES) { 1661 cost += coef_randio; 1662 } else { 1663 cost += coef_seqio; 1664 } 1665 } 1666 cost += pages * coef_page; 1667 out: 1668 *costp = cost; 1669 } 1670 1671 static u64 calc_vtime_cost(struct bio *bio, struct ioc_gq *iocg, bool is_merge) 1672 { 1673 u64 cost; 1674 1675 calc_vtime_cost_builtin(bio, iocg, is_merge, &cost); 1676 return cost; 1677 } 1678 1679 static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio) 1680 { 1681 struct blkcg_gq *blkg = bio->bi_blkg; 1682 struct ioc *ioc = rqos_to_ioc(rqos); 1683 struct ioc_gq *iocg = blkg_to_iocg(blkg); 1684 struct ioc_now now; 1685 struct iocg_wait wait; 1686 u32 hw_active, hw_inuse; 1687 u64 abs_cost, cost, vtime; 1688 1689 /* bypass IOs if disabled or for root cgroup */ 1690 if (!ioc->enabled || !iocg->level) 1691 return; 1692 1693 /* always activate so that even 0 cost IOs get protected to some level */ 1694 if (!iocg_activate(iocg, &now)) 1695 return; 1696 1697 /* calculate the absolute vtime cost */ 1698 abs_cost = calc_vtime_cost(bio, iocg, false); 1699 if (!abs_cost) 1700 return; 1701 1702 iocg->cursor = bio_end_sector(bio); 1703 1704 vtime = atomic64_read(&iocg->vtime); 1705 current_hweight(iocg, &hw_active, &hw_inuse); 1706 1707 if (hw_inuse < hw_active && 1708 time_after_eq64(vtime + ioc->inuse_margin_vtime, now.vnow)) { 1709 TRACE_IOCG_PATH(inuse_reset, iocg, &now, 1710 iocg->inuse, iocg->weight, hw_inuse, hw_active); 1711 spin_lock_irq(&ioc->lock); 1712 propagate_active_weight(iocg, iocg->weight, iocg->weight); 1713 spin_unlock_irq(&ioc->lock); 1714 current_hweight(iocg, &hw_active, &hw_inuse); 1715 } 1716 1717 cost = abs_cost_to_cost(abs_cost, hw_inuse); 1718 1719 /* 1720 * If no one's waiting and within budget, issue right away. The 1721 * tests are racy but the races aren't systemic - we only miss once 1722 * in a while which is fine. 1723 */ 1724 if (!waitqueue_active(&iocg->waitq) && 1725 !atomic64_read(&iocg->abs_vdebt) && 1726 time_before_eq64(vtime + cost, now.vnow)) { 1727 iocg_commit_bio(iocg, bio, cost); 1728 return; 1729 } 1730 1731 /* 1732 * We're over budget. If @bio has to be issued regardless, 1733 * remember the abs_cost instead of advancing vtime. 1734 * iocg_kick_waitq() will pay off the debt before waking more IOs. 1735 * This way, the debt is continuously paid off each period with the 1736 * actual budget available to the cgroup. If we just wound vtime, 1737 * we would incorrectly use the current hw_inuse for the entire 1738 * amount which, for example, can lead to the cgroup staying 1739 * blocked for a long time even with substantially raised hw_inuse. 1740 */ 1741 if (bio_issue_as_root_blkg(bio) || fatal_signal_pending(current)) { 1742 atomic64_add(abs_cost, &iocg->abs_vdebt); 1743 if (iocg_kick_delay(iocg, &now, cost)) 1744 blkcg_schedule_throttle(rqos->q, 1745 (bio->bi_opf & REQ_SWAP) == REQ_SWAP); 1746 return; 1747 } 1748 1749 /* 1750 * Append self to the waitq and schedule the wakeup timer if we're 1751 * the first waiter. The timer duration is calculated based on the 1752 * current vrate. vtime and hweight changes can make it too short 1753 * or too long. Each wait entry records the absolute cost it's 1754 * waiting for to allow re-evaluation using a custom wait entry. 1755 * 1756 * If too short, the timer simply reschedules itself. If too long, 1757 * the period timer will notice and trigger wakeups. 1758 * 1759 * All waiters are on iocg->waitq and the wait states are 1760 * synchronized using waitq.lock. 1761 */ 1762 spin_lock_irq(&iocg->waitq.lock); 1763 1764 /* 1765 * We activated above but w/o any synchronization. Deactivation is 1766 * synchronized with waitq.lock and we won't get deactivated as 1767 * long as we're waiting, so we're good if we're activated here. 1768 * In the unlikely case that we are deactivated, just issue the IO. 1769 */ 1770 if (unlikely(list_empty(&iocg->active_list))) { 1771 spin_unlock_irq(&iocg->waitq.lock); 1772 iocg_commit_bio(iocg, bio, cost); 1773 return; 1774 } 1775 1776 init_waitqueue_func_entry(&wait.wait, iocg_wake_fn); 1777 wait.wait.private = current; 1778 wait.bio = bio; 1779 wait.abs_cost = abs_cost; 1780 wait.committed = false; /* will be set true by waker */ 1781 1782 __add_wait_queue_entry_tail(&iocg->waitq, &wait.wait); 1783 iocg_kick_waitq(iocg, &now); 1784 1785 spin_unlock_irq(&iocg->waitq.lock); 1786 1787 while (true) { 1788 set_current_state(TASK_UNINTERRUPTIBLE); 1789 if (wait.committed) 1790 break; 1791 io_schedule(); 1792 } 1793 1794 /* waker already committed us, proceed */ 1795 finish_wait(&iocg->waitq, &wait.wait); 1796 } 1797 1798 static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq, 1799 struct bio *bio) 1800 { 1801 struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg); 1802 struct ioc *ioc = iocg->ioc; 1803 sector_t bio_end = bio_end_sector(bio); 1804 struct ioc_now now; 1805 u32 hw_inuse; 1806 u64 abs_cost, cost; 1807 1808 /* bypass if disabled or for root cgroup */ 1809 if (!ioc->enabled || !iocg->level) 1810 return; 1811 1812 abs_cost = calc_vtime_cost(bio, iocg, true); 1813 if (!abs_cost) 1814 return; 1815 1816 ioc_now(ioc, &now); 1817 current_hweight(iocg, NULL, &hw_inuse); 1818 cost = abs_cost_to_cost(abs_cost, hw_inuse); 1819 1820 /* update cursor if backmerging into the request at the cursor */ 1821 if (blk_rq_pos(rq) < bio_end && 1822 blk_rq_pos(rq) + blk_rq_sectors(rq) == iocg->cursor) 1823 iocg->cursor = bio_end; 1824 1825 /* 1826 * Charge if there's enough vtime budget and the existing request 1827 * has cost assigned. Otherwise, account it as debt. See debt 1828 * handling in ioc_rqos_throttle() for details. 1829 */ 1830 if (rq->bio && rq->bio->bi_iocost_cost && 1831 time_before_eq64(atomic64_read(&iocg->vtime) + cost, now.vnow)) 1832 iocg_commit_bio(iocg, bio, cost); 1833 else 1834 atomic64_add(abs_cost, &iocg->abs_vdebt); 1835 } 1836 1837 static void ioc_rqos_done_bio(struct rq_qos *rqos, struct bio *bio) 1838 { 1839 struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg); 1840 1841 if (iocg && bio->bi_iocost_cost) 1842 atomic64_add(bio->bi_iocost_cost, &iocg->done_vtime); 1843 } 1844 1845 static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq) 1846 { 1847 struct ioc *ioc = rqos_to_ioc(rqos); 1848 u64 on_q_ns, rq_wait_ns; 1849 int pidx, rw; 1850 1851 if (!ioc->enabled || !rq->alloc_time_ns || !rq->start_time_ns) 1852 return; 1853 1854 switch (req_op(rq) & REQ_OP_MASK) { 1855 case REQ_OP_READ: 1856 pidx = QOS_RLAT; 1857 rw = READ; 1858 break; 1859 case REQ_OP_WRITE: 1860 pidx = QOS_WLAT; 1861 rw = WRITE; 1862 break; 1863 default: 1864 return; 1865 } 1866 1867 on_q_ns = ktime_get_ns() - rq->alloc_time_ns; 1868 rq_wait_ns = rq->start_time_ns - rq->alloc_time_ns; 1869 1870 if (on_q_ns <= ioc->params.qos[pidx] * NSEC_PER_USEC) 1871 this_cpu_inc(ioc->pcpu_stat->missed[rw].nr_met); 1872 else 1873 this_cpu_inc(ioc->pcpu_stat->missed[rw].nr_missed); 1874 1875 this_cpu_add(ioc->pcpu_stat->rq_wait_ns, rq_wait_ns); 1876 } 1877 1878 static void ioc_rqos_queue_depth_changed(struct rq_qos *rqos) 1879 { 1880 struct ioc *ioc = rqos_to_ioc(rqos); 1881 1882 spin_lock_irq(&ioc->lock); 1883 ioc_refresh_params(ioc, false); 1884 spin_unlock_irq(&ioc->lock); 1885 } 1886 1887 static void ioc_rqos_exit(struct rq_qos *rqos) 1888 { 1889 struct ioc *ioc = rqos_to_ioc(rqos); 1890 1891 blkcg_deactivate_policy(rqos->q, &blkcg_policy_iocost); 1892 1893 spin_lock_irq(&ioc->lock); 1894 ioc->running = IOC_STOP; 1895 spin_unlock_irq(&ioc->lock); 1896 1897 del_timer_sync(&ioc->timer); 1898 free_percpu(ioc->pcpu_stat); 1899 kfree(ioc); 1900 } 1901 1902 static struct rq_qos_ops ioc_rqos_ops = { 1903 .throttle = ioc_rqos_throttle, 1904 .merge = ioc_rqos_merge, 1905 .done_bio = ioc_rqos_done_bio, 1906 .done = ioc_rqos_done, 1907 .queue_depth_changed = ioc_rqos_queue_depth_changed, 1908 .exit = ioc_rqos_exit, 1909 }; 1910 1911 static int blk_iocost_init(struct request_queue *q) 1912 { 1913 struct ioc *ioc; 1914 struct rq_qos *rqos; 1915 int ret; 1916 1917 ioc = kzalloc(sizeof(*ioc), GFP_KERNEL); 1918 if (!ioc) 1919 return -ENOMEM; 1920 1921 ioc->pcpu_stat = alloc_percpu(struct ioc_pcpu_stat); 1922 if (!ioc->pcpu_stat) { 1923 kfree(ioc); 1924 return -ENOMEM; 1925 } 1926 1927 rqos = &ioc->rqos; 1928 rqos->id = RQ_QOS_COST; 1929 rqos->ops = &ioc_rqos_ops; 1930 rqos->q = q; 1931 1932 spin_lock_init(&ioc->lock); 1933 timer_setup(&ioc->timer, ioc_timer_fn, 0); 1934 INIT_LIST_HEAD(&ioc->active_iocgs); 1935 1936 ioc->running = IOC_IDLE; 1937 atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC); 1938 seqcount_init(&ioc->period_seqcount); 1939 ioc->period_at = ktime_to_us(ktime_get()); 1940 atomic64_set(&ioc->cur_period, 0); 1941 atomic_set(&ioc->hweight_gen, 0); 1942 1943 spin_lock_irq(&ioc->lock); 1944 ioc->autop_idx = AUTOP_INVALID; 1945 ioc_refresh_params(ioc, true); 1946 spin_unlock_irq(&ioc->lock); 1947 1948 rq_qos_add(q, rqos); 1949 ret = blkcg_activate_policy(q, &blkcg_policy_iocost); 1950 if (ret) { 1951 rq_qos_del(q, rqos); 1952 free_percpu(ioc->pcpu_stat); 1953 kfree(ioc); 1954 return ret; 1955 } 1956 return 0; 1957 } 1958 1959 static struct blkcg_policy_data *ioc_cpd_alloc(gfp_t gfp) 1960 { 1961 struct ioc_cgrp *iocc; 1962 1963 iocc = kzalloc(sizeof(struct ioc_cgrp), gfp); 1964 if (!iocc) 1965 return NULL; 1966 1967 iocc->dfl_weight = CGROUP_WEIGHT_DFL; 1968 return &iocc->cpd; 1969 } 1970 1971 static void ioc_cpd_free(struct blkcg_policy_data *cpd) 1972 { 1973 kfree(container_of(cpd, struct ioc_cgrp, cpd)); 1974 } 1975 1976 static struct blkg_policy_data *ioc_pd_alloc(gfp_t gfp, struct request_queue *q, 1977 struct blkcg *blkcg) 1978 { 1979 int levels = blkcg->css.cgroup->level + 1; 1980 struct ioc_gq *iocg; 1981 1982 iocg = kzalloc_node(sizeof(*iocg) + levels * sizeof(iocg->ancestors[0]), 1983 gfp, q->node); 1984 if (!iocg) 1985 return NULL; 1986 1987 return &iocg->pd; 1988 } 1989 1990 static void ioc_pd_init(struct blkg_policy_data *pd) 1991 { 1992 struct ioc_gq *iocg = pd_to_iocg(pd); 1993 struct blkcg_gq *blkg = pd_to_blkg(&iocg->pd); 1994 struct ioc *ioc = q_to_ioc(blkg->q); 1995 struct ioc_now now; 1996 struct blkcg_gq *tblkg; 1997 unsigned long flags; 1998 1999 ioc_now(ioc, &now); 2000 2001 iocg->ioc = ioc; 2002 atomic64_set(&iocg->vtime, now.vnow); 2003 atomic64_set(&iocg->done_vtime, now.vnow); 2004 atomic64_set(&iocg->abs_vdebt, 0); 2005 atomic64_set(&iocg->active_period, atomic64_read(&ioc->cur_period)); 2006 INIT_LIST_HEAD(&iocg->active_list); 2007 iocg->hweight_active = HWEIGHT_WHOLE; 2008 iocg->hweight_inuse = HWEIGHT_WHOLE; 2009 2010 init_waitqueue_head(&iocg->waitq); 2011 hrtimer_init(&iocg->waitq_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); 2012 iocg->waitq_timer.function = iocg_waitq_timer_fn; 2013 hrtimer_init(&iocg->delay_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); 2014 iocg->delay_timer.function = iocg_delay_timer_fn; 2015 2016 iocg->level = blkg->blkcg->css.cgroup->level; 2017 2018 for (tblkg = blkg; tblkg; tblkg = tblkg->parent) { 2019 struct ioc_gq *tiocg = blkg_to_iocg(tblkg); 2020 iocg->ancestors[tiocg->level] = tiocg; 2021 } 2022 2023 spin_lock_irqsave(&ioc->lock, flags); 2024 weight_updated(iocg); 2025 spin_unlock_irqrestore(&ioc->lock, flags); 2026 } 2027 2028 static void ioc_pd_free(struct blkg_policy_data *pd) 2029 { 2030 struct ioc_gq *iocg = pd_to_iocg(pd); 2031 struct ioc *ioc = iocg->ioc; 2032 2033 if (ioc) { 2034 spin_lock(&ioc->lock); 2035 if (!list_empty(&iocg->active_list)) { 2036 propagate_active_weight(iocg, 0, 0); 2037 list_del_init(&iocg->active_list); 2038 } 2039 spin_unlock(&ioc->lock); 2040 2041 hrtimer_cancel(&iocg->waitq_timer); 2042 hrtimer_cancel(&iocg->delay_timer); 2043 } 2044 kfree(iocg); 2045 } 2046 2047 static u64 ioc_weight_prfill(struct seq_file *sf, struct blkg_policy_data *pd, 2048 int off) 2049 { 2050 const char *dname = blkg_dev_name(pd->blkg); 2051 struct ioc_gq *iocg = pd_to_iocg(pd); 2052 2053 if (dname && iocg->cfg_weight) 2054 seq_printf(sf, "%s %u\n", dname, iocg->cfg_weight); 2055 return 0; 2056 } 2057 2058 2059 static int ioc_weight_show(struct seq_file *sf, void *v) 2060 { 2061 struct blkcg *blkcg = css_to_blkcg(seq_css(sf)); 2062 struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg); 2063 2064 seq_printf(sf, "default %u\n", iocc->dfl_weight); 2065 blkcg_print_blkgs(sf, blkcg, ioc_weight_prfill, 2066 &blkcg_policy_iocost, seq_cft(sf)->private, false); 2067 return 0; 2068 } 2069 2070 static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf, 2071 size_t nbytes, loff_t off) 2072 { 2073 struct blkcg *blkcg = css_to_blkcg(of_css(of)); 2074 struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg); 2075 struct blkg_conf_ctx ctx; 2076 struct ioc_gq *iocg; 2077 u32 v; 2078 int ret; 2079 2080 if (!strchr(buf, ':')) { 2081 struct blkcg_gq *blkg; 2082 2083 if (!sscanf(buf, "default %u", &v) && !sscanf(buf, "%u", &v)) 2084 return -EINVAL; 2085 2086 if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX) 2087 return -EINVAL; 2088 2089 spin_lock(&blkcg->lock); 2090 iocc->dfl_weight = v; 2091 hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) { 2092 struct ioc_gq *iocg = blkg_to_iocg(blkg); 2093 2094 if (iocg) { 2095 spin_lock_irq(&iocg->ioc->lock); 2096 weight_updated(iocg); 2097 spin_unlock_irq(&iocg->ioc->lock); 2098 } 2099 } 2100 spin_unlock(&blkcg->lock); 2101 2102 return nbytes; 2103 } 2104 2105 ret = blkg_conf_prep(blkcg, &blkcg_policy_iocost, buf, &ctx); 2106 if (ret) 2107 return ret; 2108 2109 iocg = blkg_to_iocg(ctx.blkg); 2110 2111 if (!strncmp(ctx.body, "default", 7)) { 2112 v = 0; 2113 } else { 2114 if (!sscanf(ctx.body, "%u", &v)) 2115 goto einval; 2116 if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX) 2117 goto einval; 2118 } 2119 2120 spin_lock(&iocg->ioc->lock); 2121 iocg->cfg_weight = v; 2122 weight_updated(iocg); 2123 spin_unlock(&iocg->ioc->lock); 2124 2125 blkg_conf_finish(&ctx); 2126 return nbytes; 2127 2128 einval: 2129 blkg_conf_finish(&ctx); 2130 return -EINVAL; 2131 } 2132 2133 static u64 ioc_qos_prfill(struct seq_file *sf, struct blkg_policy_data *pd, 2134 int off) 2135 { 2136 const char *dname = blkg_dev_name(pd->blkg); 2137 struct ioc *ioc = pd_to_iocg(pd)->ioc; 2138 2139 if (!dname) 2140 return 0; 2141 2142 seq_printf(sf, "%s enable=%d ctrl=%s rpct=%u.%02u rlat=%u wpct=%u.%02u wlat=%u min=%u.%02u max=%u.%02u\n", 2143 dname, ioc->enabled, ioc->user_qos_params ? "user" : "auto", 2144 ioc->params.qos[QOS_RPPM] / 10000, 2145 ioc->params.qos[QOS_RPPM] % 10000 / 100, 2146 ioc->params.qos[QOS_RLAT], 2147 ioc->params.qos[QOS_WPPM] / 10000, 2148 ioc->params.qos[QOS_WPPM] % 10000 / 100, 2149 ioc->params.qos[QOS_WLAT], 2150 ioc->params.qos[QOS_MIN] / 10000, 2151 ioc->params.qos[QOS_MIN] % 10000 / 100, 2152 ioc->params.qos[QOS_MAX] / 10000, 2153 ioc->params.qos[QOS_MAX] % 10000 / 100); 2154 return 0; 2155 } 2156 2157 static int ioc_qos_show(struct seq_file *sf, void *v) 2158 { 2159 struct blkcg *blkcg = css_to_blkcg(seq_css(sf)); 2160 2161 blkcg_print_blkgs(sf, blkcg, ioc_qos_prfill, 2162 &blkcg_policy_iocost, seq_cft(sf)->private, false); 2163 return 0; 2164 } 2165 2166 static const match_table_t qos_ctrl_tokens = { 2167 { QOS_ENABLE, "enable=%u" }, 2168 { QOS_CTRL, "ctrl=%s" }, 2169 { NR_QOS_CTRL_PARAMS, NULL }, 2170 }; 2171 2172 static const match_table_t qos_tokens = { 2173 { QOS_RPPM, "rpct=%s" }, 2174 { QOS_RLAT, "rlat=%u" }, 2175 { QOS_WPPM, "wpct=%s" }, 2176 { QOS_WLAT, "wlat=%u" }, 2177 { QOS_MIN, "min=%s" }, 2178 { QOS_MAX, "max=%s" }, 2179 { NR_QOS_PARAMS, NULL }, 2180 }; 2181 2182 static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input, 2183 size_t nbytes, loff_t off) 2184 { 2185 struct gendisk *disk; 2186 struct ioc *ioc; 2187 u32 qos[NR_QOS_PARAMS]; 2188 bool enable, user; 2189 char *p; 2190 int ret; 2191 2192 disk = blkcg_conf_get_disk(&input); 2193 if (IS_ERR(disk)) 2194 return PTR_ERR(disk); 2195 2196 ioc = q_to_ioc(disk->queue); 2197 if (!ioc) { 2198 ret = blk_iocost_init(disk->queue); 2199 if (ret) 2200 goto err; 2201 ioc = q_to_ioc(disk->queue); 2202 } 2203 2204 spin_lock_irq(&ioc->lock); 2205 memcpy(qos, ioc->params.qos, sizeof(qos)); 2206 enable = ioc->enabled; 2207 user = ioc->user_qos_params; 2208 spin_unlock_irq(&ioc->lock); 2209 2210 while ((p = strsep(&input, " \t\n"))) { 2211 substring_t args[MAX_OPT_ARGS]; 2212 char buf[32]; 2213 int tok; 2214 s64 v; 2215 2216 if (!*p) 2217 continue; 2218 2219 switch (match_token(p, qos_ctrl_tokens, args)) { 2220 case QOS_ENABLE: 2221 match_u64(&args[0], &v); 2222 enable = v; 2223 continue; 2224 case QOS_CTRL: 2225 match_strlcpy(buf, &args[0], sizeof(buf)); 2226 if (!strcmp(buf, "auto")) 2227 user = false; 2228 else if (!strcmp(buf, "user")) 2229 user = true; 2230 else 2231 goto einval; 2232 continue; 2233 } 2234 2235 tok = match_token(p, qos_tokens, args); 2236 switch (tok) { 2237 case QOS_RPPM: 2238 case QOS_WPPM: 2239 if (match_strlcpy(buf, &args[0], sizeof(buf)) >= 2240 sizeof(buf)) 2241 goto einval; 2242 if (cgroup_parse_float(buf, 2, &v)) 2243 goto einval; 2244 if (v < 0 || v > 10000) 2245 goto einval; 2246 qos[tok] = v * 100; 2247 break; 2248 case QOS_RLAT: 2249 case QOS_WLAT: 2250 if (match_u64(&args[0], &v)) 2251 goto einval; 2252 qos[tok] = v; 2253 break; 2254 case QOS_MIN: 2255 case QOS_MAX: 2256 if (match_strlcpy(buf, &args[0], sizeof(buf)) >= 2257 sizeof(buf)) 2258 goto einval; 2259 if (cgroup_parse_float(buf, 2, &v)) 2260 goto einval; 2261 if (v < 0) 2262 goto einval; 2263 qos[tok] = clamp_t(s64, v * 100, 2264 VRATE_MIN_PPM, VRATE_MAX_PPM); 2265 break; 2266 default: 2267 goto einval; 2268 } 2269 user = true; 2270 } 2271 2272 if (qos[QOS_MIN] > qos[QOS_MAX]) 2273 goto einval; 2274 2275 spin_lock_irq(&ioc->lock); 2276 2277 if (enable) { 2278 blk_queue_flag_set(QUEUE_FLAG_RQ_ALLOC_TIME, ioc->rqos.q); 2279 ioc->enabled = true; 2280 } else { 2281 blk_queue_flag_clear(QUEUE_FLAG_RQ_ALLOC_TIME, ioc->rqos.q); 2282 ioc->enabled = false; 2283 } 2284 2285 if (user) { 2286 memcpy(ioc->params.qos, qos, sizeof(qos)); 2287 ioc->user_qos_params = true; 2288 } else { 2289 ioc->user_qos_params = false; 2290 } 2291 2292 ioc_refresh_params(ioc, true); 2293 spin_unlock_irq(&ioc->lock); 2294 2295 put_disk_and_module(disk); 2296 return nbytes; 2297 einval: 2298 ret = -EINVAL; 2299 err: 2300 put_disk_and_module(disk); 2301 return ret; 2302 } 2303 2304 static u64 ioc_cost_model_prfill(struct seq_file *sf, 2305 struct blkg_policy_data *pd, int off) 2306 { 2307 const char *dname = blkg_dev_name(pd->blkg); 2308 struct ioc *ioc = pd_to_iocg(pd)->ioc; 2309 u64 *u = ioc->params.i_lcoefs; 2310 2311 if (!dname) 2312 return 0; 2313 2314 seq_printf(sf, "%s ctrl=%s model=linear " 2315 "rbps=%llu rseqiops=%llu rrandiops=%llu " 2316 "wbps=%llu wseqiops=%llu wrandiops=%llu\n", 2317 dname, ioc->user_cost_model ? "user" : "auto", 2318 u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS], 2319 u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS]); 2320 return 0; 2321 } 2322 2323 static int ioc_cost_model_show(struct seq_file *sf, void *v) 2324 { 2325 struct blkcg *blkcg = css_to_blkcg(seq_css(sf)); 2326 2327 blkcg_print_blkgs(sf, blkcg, ioc_cost_model_prfill, 2328 &blkcg_policy_iocost, seq_cft(sf)->private, false); 2329 return 0; 2330 } 2331 2332 static const match_table_t cost_ctrl_tokens = { 2333 { COST_CTRL, "ctrl=%s" }, 2334 { COST_MODEL, "model=%s" }, 2335 { NR_COST_CTRL_PARAMS, NULL }, 2336 }; 2337 2338 static const match_table_t i_lcoef_tokens = { 2339 { I_LCOEF_RBPS, "rbps=%u" }, 2340 { I_LCOEF_RSEQIOPS, "rseqiops=%u" }, 2341 { I_LCOEF_RRANDIOPS, "rrandiops=%u" }, 2342 { I_LCOEF_WBPS, "wbps=%u" }, 2343 { I_LCOEF_WSEQIOPS, "wseqiops=%u" }, 2344 { I_LCOEF_WRANDIOPS, "wrandiops=%u" }, 2345 { NR_I_LCOEFS, NULL }, 2346 }; 2347 2348 static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, 2349 size_t nbytes, loff_t off) 2350 { 2351 struct gendisk *disk; 2352 struct ioc *ioc; 2353 u64 u[NR_I_LCOEFS]; 2354 bool user; 2355 char *p; 2356 int ret; 2357 2358 disk = blkcg_conf_get_disk(&input); 2359 if (IS_ERR(disk)) 2360 return PTR_ERR(disk); 2361 2362 ioc = q_to_ioc(disk->queue); 2363 if (!ioc) { 2364 ret = blk_iocost_init(disk->queue); 2365 if (ret) 2366 goto err; 2367 ioc = q_to_ioc(disk->queue); 2368 } 2369 2370 spin_lock_irq(&ioc->lock); 2371 memcpy(u, ioc->params.i_lcoefs, sizeof(u)); 2372 user = ioc->user_cost_model; 2373 spin_unlock_irq(&ioc->lock); 2374 2375 while ((p = strsep(&input, " \t\n"))) { 2376 substring_t args[MAX_OPT_ARGS]; 2377 char buf[32]; 2378 int tok; 2379 u64 v; 2380 2381 if (!*p) 2382 continue; 2383 2384 switch (match_token(p, cost_ctrl_tokens, args)) { 2385 case COST_CTRL: 2386 match_strlcpy(buf, &args[0], sizeof(buf)); 2387 if (!strcmp(buf, "auto")) 2388 user = false; 2389 else if (!strcmp(buf, "user")) 2390 user = true; 2391 else 2392 goto einval; 2393 continue; 2394 case COST_MODEL: 2395 match_strlcpy(buf, &args[0], sizeof(buf)); 2396 if (strcmp(buf, "linear")) 2397 goto einval; 2398 continue; 2399 } 2400 2401 tok = match_token(p, i_lcoef_tokens, args); 2402 if (tok == NR_I_LCOEFS) 2403 goto einval; 2404 if (match_u64(&args[0], &v)) 2405 goto einval; 2406 u[tok] = v; 2407 user = true; 2408 } 2409 2410 spin_lock_irq(&ioc->lock); 2411 if (user) { 2412 memcpy(ioc->params.i_lcoefs, u, sizeof(u)); 2413 ioc->user_cost_model = true; 2414 } else { 2415 ioc->user_cost_model = false; 2416 } 2417 ioc_refresh_params(ioc, true); 2418 spin_unlock_irq(&ioc->lock); 2419 2420 put_disk_and_module(disk); 2421 return nbytes; 2422 2423 einval: 2424 ret = -EINVAL; 2425 err: 2426 put_disk_and_module(disk); 2427 return ret; 2428 } 2429 2430 static struct cftype ioc_files[] = { 2431 { 2432 .name = "weight", 2433 .flags = CFTYPE_NOT_ON_ROOT, 2434 .seq_show = ioc_weight_show, 2435 .write = ioc_weight_write, 2436 }, 2437 { 2438 .name = "cost.qos", 2439 .flags = CFTYPE_ONLY_ON_ROOT, 2440 .seq_show = ioc_qos_show, 2441 .write = ioc_qos_write, 2442 }, 2443 { 2444 .name = "cost.model", 2445 .flags = CFTYPE_ONLY_ON_ROOT, 2446 .seq_show = ioc_cost_model_show, 2447 .write = ioc_cost_model_write, 2448 }, 2449 {} 2450 }; 2451 2452 static struct blkcg_policy blkcg_policy_iocost = { 2453 .dfl_cftypes = ioc_files, 2454 .cpd_alloc_fn = ioc_cpd_alloc, 2455 .cpd_free_fn = ioc_cpd_free, 2456 .pd_alloc_fn = ioc_pd_alloc, 2457 .pd_init_fn = ioc_pd_init, 2458 .pd_free_fn = ioc_pd_free, 2459 }; 2460 2461 static int __init ioc_init(void) 2462 { 2463 return blkcg_policy_register(&blkcg_policy_iocost); 2464 } 2465 2466 static void __exit ioc_exit(void) 2467 { 2468 return blkcg_policy_unregister(&blkcg_policy_iocost); 2469 } 2470 2471 module_init(ioc_init); 2472 module_exit(ioc_exit); 2473