block/bfq-iosched.h

   1 /*
   2  * Header file for the BFQ I/O scheduler: data structures and
   3  * prototypes of interface functions among BFQ components.
   4  *
   5  *  This program is free software; you can redistribute it and/or
   6  *  modify it under the terms of the GNU General Public License as
   7  *  published by the Free Software Foundation; either version 2 of the
   8  *  License, or (at your option) any later version.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  *  General Public License for more details.
  14  */
  15 #ifndef _BFQ_H
  16 #define _BFQ_H
  17
  18 #include <linux/blktrace_api.h>
  19 #include <linux/hrtimer.h>
  20 #include <linux/blk-cgroup.h>
  21
  22 #define BFQ_IOPRIO_CLASSES      3
  23 #define BFQ_CL_IDLE_TIMEOUT     (HZ/5)
  24
  25 #define BFQ_MIN_WEIGHT                  1
  26 #define BFQ_MAX_WEIGHT                  1000
  27 #define BFQ_WEIGHT_CONVERSION_COEFF     10
  28
  29 #define BFQ_DEFAULT_QUEUE_IOPRIO        4
  30
  31 #define BFQ_WEIGHT_LEGACY_DFL   100
  32 #define BFQ_DEFAULT_GRP_IOPRIO  0
  33 #define BFQ_DEFAULT_GRP_CLASS   IOPRIO_CLASS_BE
  34
  35 /*
  36  * Soft real-time applications are extremely more latency sensitive
  37  * than interactive ones. Over-raise the weight of the former to
  38  * privilege them against the latter.
  39  */
  40 #define BFQ_SOFTRT_WEIGHT_FACTOR        100
  41
  42 struct bfq_entity;
  43
  44 /**
  45  * struct bfq_service_tree - per ioprio_class service tree.
  46  *
  47  * Each service tree represents a B-WF2Q+ scheduler on its own.  Each
  48  * ioprio_class has its own independent scheduler, and so its own
  49  * bfq_service_tree.  All the fields are protected by the queue lock
  50  * of the containing bfqd.
  51  */
  52 struct bfq_service_tree {
  53         /* tree for active entities (i.e., those backlogged) */
  54         struct rb_root active;
  55         /* tree for idle entities (i.e., not backlogged, with V < F_i)*/
  56         struct rb_root idle;
  57
  58         /* idle entity with minimum F_i */
  59         struct bfq_entity *first_idle;
  60         /* idle entity with maximum F_i */
  61         struct bfq_entity *last_idle;
  62
  63         /* scheduler virtual time */
  64         u64 vtime;
  65         /* scheduler weight sum; active and idle entities contribute to it */
  66         unsigned long wsum;
  67 };
  68
  69 /**
  70  * struct bfq_sched_data - multi-class scheduler.
  71  *
  72  * bfq_sched_data is the basic scheduler queue.  It supports three
  73  * ioprio_classes, and can be used either as a toplevel queue or as an
  74  * intermediate queue in a hierarchical setup.
  75  *
  76  * The supported ioprio_classes are the same as in CFQ, in descending
  77  * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE.
  78  * Requests from higher priority queues are served before all the
  79  * requests from lower priority queues; among requests of the same
  80  * queue requests are served according to B-WF2Q+.
  81  *
  82  * The schedule is implemented by the service trees, plus the field
  83  * @next_in_service, which points to the entity on the active trees
  84  * that will be served next, if 1) no changes in the schedule occurs
  85  * before the current in-service entity is expired, 2) the in-service
  86  * queue becomes idle when it expires, and 3) if the entity pointed by
  87  * in_service_entity is not a queue, then the in-service child entity
  88  * of the entity pointed by in_service_entity becomes idle on
  89  * expiration. This peculiar definition allows for the following
  90  * optimization, not yet exploited: while a given entity is still in
  91  * service, we already know which is the best candidate for next
  92  * service among the other active entitities in the same parent
  93  * entity. We can then quickly compare the timestamps of the
  94  * in-service entity with those of such best candidate.
  95  *
  96  * All fields are protected by the lock of the containing bfqd.
  97  */
  98 struct bfq_sched_data {
  99         /* entity in service */
 100         struct bfq_entity *in_service_entity;
 101         /* head-of-line entity (see comments above) */
 102         struct bfq_entity *next_in_service;
 103         /* array of service trees, one per ioprio_class */
 104         struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES];
 105         /* last time CLASS_IDLE was served */
 106         unsigned long bfq_class_idle_last_service;
 107
 108 };
 109
 110 /**
 111  * struct bfq_weight_counter - counter of the number of all active queues
 112  *                             with a given weight.
 113  */
 114 struct bfq_weight_counter {
 115         unsigned int weight; /* weight of the queues this counter refers to */
 116         unsigned int num_active; /* nr of active queues with this weight */
 117         /*
 118          * Weights tree member (see bfq_data's @queue_weights_tree)
 119          */
 120         struct rb_node weights_node;
 121 };
 122
 123 /**
 124  * struct bfq_entity - schedulable entity.
 125  *
 126  * A bfq_entity is used to represent either a bfq_queue (leaf node in the
 127  * cgroup hierarchy) or a bfq_group into the upper level scheduler.  Each
 128  * entity belongs to the sched_data of the parent group in the cgroup
 129  * hierarchy.  Non-leaf entities have also their own sched_data, stored
 130  * in @my_sched_data.
 131  *
 132  * Each entity stores independently its priority values; this would
 133  * allow different weights on different devices, but this
 134  * functionality is not exported to userspace by now.  Priorities and
 135  * weights are updated lazily, first storing the new values into the
 136  * new_* fields, then setting the @prio_changed flag.  As soon as
 137  * there is a transition in the entity state that allows the priority
 138  * update to take place the effective and the requested priority
 139  * values are synchronized.
 140  *
 141  * Unless cgroups are used, the weight value is calculated from the
 142  * ioprio to export the same interface as CFQ.  When dealing with
 143  * ``well-behaved'' queues (i.e., queues that do not spend too much
 144  * time to consume their budget and have true sequential behavior, and
 145  * when there are no external factors breaking anticipation) the
 146  * relative weights at each level of the cgroups hierarchy should be
 147  * guaranteed.  All the fields are protected by the queue lock of the
 148  * containing bfqd.
 149  */
 150 struct bfq_entity {
 151         /* service_tree member */
 152         struct rb_node rb_node;
 153
 154         /*
 155          * Flag, true if the entity is on a tree (either the active or
 156          * the idle one of its service_tree) or is in service.
 157          */
 158         bool on_st;
 159
 160         /* B-WF2Q+ start and finish timestamps [sectors/weight] */
 161         u64 start, finish;
 162
 163         /* tree the entity is enqueued into; %NULL if not on a tree */
 164         struct rb_root *tree;
 165
 166         /*
 167          * minimum start time of the (active) subtree rooted at this
 168          * entity; used for O(log N) lookups into active trees
 169          */
 170         u64 min_start;
 171
 172         /* amount of service received during the last service slot */
 173         int service;
 174
 175         /* budget, used also to calculate F_i: F_i = S_i + @budget / @weight */
 176         int budget;
 177
 178         /* weight of the queue */
 179         int weight;
 180         /* next weight if a change is in progress */
 181         int new_weight;
 182
 183         /* original weight, used to implement weight boosting */
 184         int orig_weight;
 185
 186         /* parent entity, for hierarchical scheduling */
 187         struct bfq_entity *parent;
 188
 189         /*
 190          * For non-leaf nodes in the hierarchy, the associated
 191          * scheduler queue, %NULL on leaf nodes.
 192          */
 193         struct bfq_sched_data *my_sched_data;
 194         /* the scheduler queue this entity belongs to */
 195         struct bfq_sched_data *sched_data;
 196
 197         /* flag, set to request a weight, ioprio or ioprio_class change  */
 198         int prio_changed;
 199
 200         /* flag, set if the entity is counted in groups_with_pending_reqs */
 201         bool in_groups_with_pending_reqs;
 202 };
 203
 204 struct bfq_group;
 205
 206 /**
 207  * struct bfq_ttime - per process thinktime stats.
 208  */
 209 struct bfq_ttime {
 210         /* completion time of the last request */
 211         u64 last_end_request;
 212
 213         /* total process thinktime */
 214         u64 ttime_total;
 215         /* number of thinktime samples */
 216         unsigned long ttime_samples;
 217         /* average process thinktime */
 218         u64 ttime_mean;
 219 };
 220
 221 /**
 222  * struct bfq_queue - leaf schedulable entity.
 223  *
 224  * A bfq_queue is a leaf request queue; it can be associated with an
 225  * io_context or more, if it  is  async or shared  between  cooperating
 226  * processes. @cgroup holds a reference to the cgroup, to be sure that it
 227  * does not disappear while a bfqq still references it (mostly to avoid
 228  * races between request issuing and task migration followed by cgroup
 229  * destruction).
 230  * All the fields are protected by the queue lock of the containing bfqd.
 231  */
 232 struct bfq_queue {
 233         /* reference counter */
 234         int ref;
 235         /* parent bfq_data */
 236         struct bfq_data *bfqd;
 237
 238         /* current ioprio and ioprio class */
 239         unsigned short ioprio, ioprio_class;
 240         /* next ioprio and ioprio class if a change is in progress */
 241         unsigned short new_ioprio, new_ioprio_class;
 242
 243         /*
 244          * Shared bfq_queue if queue is cooperating with one or more
 245          * other queues.
 246          */
 247         struct bfq_queue *new_bfqq;
 248         /* request-position tree member (see bfq_group's @rq_pos_tree) */
 249         struct rb_node pos_node;
 250         /* request-position tree root (see bfq_group's @rq_pos_tree) */
 251         struct rb_root *pos_root;
 252
 253         /* sorted list of pending requests */
 254         struct rb_root sort_list;
 255         /* if fifo isn't expired, next request to serve */
 256         struct request *next_rq;
 257         /* number of sync and async requests queued */
 258         int queued[2];
 259         /* number of requests currently allocated */
 260         int allocated;
 261         /* number of pending metadata requests */
 262         int meta_pending;
 263         /* fifo list of requests in sort_list */
 264         struct list_head fifo;
 265
 266         /* entity representing this queue in the scheduler */
 267         struct bfq_entity entity;
 268
 269         /* pointer to the weight counter associated with this entity */
 270         struct bfq_weight_counter *weight_counter;
 271
 272         /* maximum budget allowed from the feedback mechanism */
 273         int max_budget;
 274         /* budget expiration (in jiffies) */
 275         unsigned long budget_timeout;
 276
 277         /* number of requests on the dispatch list or inside driver */
 278         int dispatched;
 279
 280         /* status flags */
 281         unsigned long flags;
 282
 283         /* node for active/idle bfqq list inside parent bfqd */
 284         struct list_head bfqq_list;
 285
 286         /* associated @bfq_ttime struct */
 287         struct bfq_ttime ttime;
 288
 289         /* bit vector: a 1 for each seeky requests in history */
 290         u32 seek_history;
 291
 292         /* node for the device's burst list */
 293         struct hlist_node burst_list_node;
 294
 295         /* position of the last request enqueued */
 296         sector_t last_request_pos;
 297
 298         /* Number of consecutive pairs of request completion and
 299          * arrival, such that the queue becomes idle after the
 300          * completion, but the next request arrives within an idle
 301          * time slice; used only if the queue's IO_bound flag has been
 302          * cleared.
 303          */
 304         unsigned int requests_within_timer;
 305
 306         /* pid of the process owning the queue, used for logging purposes */
 307         pid_t pid;
 308
 309         /*
 310          * Pointer to the bfq_io_cq owning the bfq_queue, set to %NULL
 311          * if the queue is shared.
 312          */
 313         struct bfq_io_cq *bic;
 314
 315         /* current maximum weight-raising time for this queue */
 316         unsigned long wr_cur_max_time;
 317         /*
 318          * Minimum time instant such that, only if a new request is
 319          * enqueued after this time instant in an idle @bfq_queue with
 320          * no outstanding requests, then the task associated with the
 321          * queue it is deemed as soft real-time (see the comments on
 322          * the function bfq_bfqq_softrt_next_start())
 323          */
 324         unsigned long soft_rt_next_start;
 325         /*
 326          * Start time of the current weight-raising period if
 327          * the @bfq-queue is being weight-raised, otherwise
 328          * finish time of the last weight-raising period.
 329          */
 330         unsigned long last_wr_start_finish;
 331         /* factor by which the weight of this queue is multiplied */
 332         unsigned int wr_coeff;
 333         /*
 334          * Time of the last transition of the @bfq_queue from idle to
 335          * backlogged.
 336          */
 337         unsigned long last_idle_bklogged;
 338         /*
 339          * Cumulative service received from the @bfq_queue since the
 340          * last transition from idle to backlogged.
 341          */
 342         unsigned long service_from_backlogged;
 343         /*
 344          * Cumulative service received from the @bfq_queue since its
 345          * last transition to weight-raised state.
 346          */
 347         unsigned long service_from_wr;
 348
 349         /*
 350          * Value of wr start time when switching to soft rt
 351          */
 352         unsigned long wr_start_at_switch_to_srt;
 353
 354         unsigned long split_time; /* time of last split */
 355
 356         unsigned long first_IO_time; /* time of first I/O for this queue */
 357
 358         /* max service rate measured so far */
 359         u32 max_service_rate;
 360         /*
 361          * Ratio between the service received by bfqq while it is in
 362          * service, and the cumulative service (of requests of other
 363          * queues) that may be injected while bfqq is empty but still
 364          * in service. To increase precision, the coefficient is
 365          * measured in tenths of unit. Here are some example of (1)
 366          * ratios, (2) resulting percentages of service injected
 367          * w.r.t. to the total service dispatched while bfqq is in
 368          * service, and (3) corresponding values of the coefficient:
 369          * 1 (50%) -> 10
 370          * 2 (33%) -> 20
 371          * 10 (9%) -> 100
 372          * 9.9 (9%) -> 99
 373          * 1.5 (40%) -> 15
 374          * 0.5 (66%) -> 5
 375          * 0.1 (90%) -> 1
 376          *
 377          * So, if the coefficient is lower than 10, then
 378          * injected service is more than bfqq service.
 379          */
 380         unsigned int inject_coeff;
 381         /* amount of service injected in current service slot */
 382         unsigned int injected_service;
 383 };
 384
 385 /**
 386  * struct bfq_io_cq - per (request_queue, io_context) structure.
 387  */
 388 struct bfq_io_cq {
 389         /* associated io_cq structure */
 390         struct io_cq icq; /* must be the first member */
 391         /* array of two process queues, the sync and the async */
 392         struct bfq_queue *bfqq[2];
 393         /* per (request_queue, blkcg) ioprio */
 394         int ioprio;
 395 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 396         uint64_t blkcg_serial_nr; /* the current blkcg serial */
 397 #endif
 398         /*
 399          * Snapshot of the has_short_time flag before merging; taken
 400          * to remember its value while the queue is merged, so as to
 401          * be able to restore it in case of split.
 402          */
 403         bool saved_has_short_ttime;
 404         /*
 405          * Same purpose as the previous two fields for the I/O bound
 406          * classification of a queue.
 407          */
 408         bool saved_IO_bound;
 409
 410         /*
 411          * Same purpose as the previous fields for the value of the
 412          * field keeping the queue's belonging to a large burst
 413          */
 414         bool saved_in_large_burst;
 415         /*
 416          * True if the queue belonged to a burst list before its merge
 417          * with another cooperating queue.
 418          */
 419         bool was_in_burst_list;
 420
 421         /*
 422          * Similar to previous fields: save wr information.
 423          */
 424         unsigned long saved_wr_coeff;
 425         unsigned long saved_last_wr_start_finish;
 426         unsigned long saved_wr_start_at_switch_to_srt;
 427         unsigned int saved_wr_cur_max_time;
 428         struct bfq_ttime saved_ttime;
 429 };
 430
 431 /**
 432  * struct bfq_data - per-device data structure.
 433  *
 434  * All the fields are protected by @lock.
 435  */
 436 struct bfq_data {
 437         /* device request queue */
 438         struct request_queue *queue;
 439         /* dispatch queue */
 440         struct list_head dispatch;
 441
 442         /* root bfq_group for the device */
 443         struct bfq_group *root_group;
 444
 445         /*
 446          * rbtree of weight counters of @bfq_queues, sorted by
 447          * weight. Used to keep track of whether all @bfq_queues have
 448          * the same weight. The tree contains one counter for each
 449          * distinct weight associated to some active and not
 450          * weight-raised @bfq_queue (see the comments to the functions
 451          * bfq_weights_tree_[add|remove] for further details).
 452          */
 453         struct rb_root queue_weights_tree;
 454
 455         /*
 456          * Number of groups with at least one descendant process that
 457          * has at least one request waiting for completion. Note that
 458          * this accounts for also requests already dispatched, but not
 459          * yet completed. Therefore this number of groups may differ
 460          * (be larger) than the number of active groups, as a group is
 461          * considered active only if its corresponding entity has
 462          * descendant queues with at least one request queued. This
 463          * number is used to decide whether a scenario is symmetric.
 464          * For a detailed explanation see comments on the computation
 465          * of the variable asymmetric_scenario in the function
 466          * bfq_better_to_idle().
 467          *
 468          * However, it is hard to compute this number exactly, for
 469          * groups with multiple descendant processes. Consider a group
 470          * that is inactive, i.e., that has no descendant process with
 471          * pending I/O inside BFQ queues. Then suppose that
 472          * num_groups_with_pending_reqs is still accounting for this
 473          * group, because the group has descendant processes with some
 474          * I/O request still in flight. num_groups_with_pending_reqs
 475          * should be decremented when the in-flight request of the
 476          * last descendant process is finally completed (assuming that
 477          * nothing else has changed for the group in the meantime, in
 478          * terms of composition of the group and active/inactive state of child
 479          * groups and processes). To accomplish this, an additional
 480          * pending-request counter must be added to entities, and must
 481          * be updated correctly. To avoid this additional field and operations,
 482          * we resort to the following tradeoff between simplicity and
 483          * accuracy: for an inactive group that is still counted in
 484          * num_groups_with_pending_reqs, we decrement
 485          * num_groups_with_pending_reqs when the first descendant
 486          * process of the group remains with no request waiting for
 487          * completion.
 488          *
 489          * Even this simpler decrement strategy requires a little
 490          * carefulness: to avoid multiple decrements, we flag a group,
 491          * more precisely an entity representing a group, as still
 492          * counted in num_groups_with_pending_reqs when it becomes
 493          * inactive. Then, when the first descendant queue of the
 494          * entity remains with no request waiting for completion,
 495          * num_groups_with_pending_reqs is decremented, and this flag
 496          * is reset. After this flag is reset for the entity,
 497          * num_groups_with_pending_reqs won't be decremented any
 498          * longer in case a new descendant queue of the entity remains
 499          * with no request waiting for completion.
 500          */
 501         unsigned int num_groups_with_pending_reqs;
 502
 503         /*
 504          * Per-class (RT, BE, IDLE) number of bfq_queues containing
 505          * requests (including the queue in service, even if it is
 506          * idling).
 507          */
 508         unsigned int busy_queues[3];
 509         /* number of weight-raised busy @bfq_queues */
 510         int wr_busy_queues;
 511         /* number of queued requests */
 512         int queued;
 513         /* number of requests dispatched and waiting for completion */
 514         int rq_in_driver;
 515
 516         /*
 517          * Maximum number of requests in driver in the last
 518          * @hw_tag_samples completed requests.
 519          */
 520         int max_rq_in_driver;
 521         /* number of samples used to calculate hw_tag */
 522         int hw_tag_samples;
 523         /* flag set to one if the driver is showing a queueing behavior */
 524         int hw_tag;
 525
 526         /* number of budgets assigned */
 527         int budgets_assigned;
 528
 529         /*
 530          * Timer set when idling (waiting) for the next request from
 531          * the queue in service.
 532          */
 533         struct hrtimer idle_slice_timer;
 534
 535         /* bfq_queue in service */
 536         struct bfq_queue *in_service_queue;
 537
 538         /* on-disk position of the last served request */
 539         sector_t last_position;
 540
 541         /* position of the last served request for the in-service queue */
 542         sector_t in_serv_last_pos;
 543
 544         /* time of last request completion (ns) */
 545         u64 last_completion;
 546
 547         /* time of first rq dispatch in current observation interval (ns) */
 548         u64 first_dispatch;
 549         /* time of last rq dispatch in current observation interval (ns) */
 550         u64 last_dispatch;
 551
 552         /* beginning of the last budget */
 553         ktime_t last_budget_start;
 554         /* beginning of the last idle slice */
 555         ktime_t last_idling_start;
 556
 557         /* number of samples in current observation interval */
 558         int peak_rate_samples;
 559         /* num of samples of seq dispatches in current observation interval */
 560         u32 sequential_samples;
 561         /* total num of sectors transferred in current observation interval */
 562         u64 tot_sectors_dispatched;
 563         /* max rq size seen during current observation interval (sectors) */
 564         u32 last_rq_max_size;
 565         /* time elapsed from first dispatch in current observ. interval (us) */
 566         u64 delta_from_first;
 567         /*
 568          * Current estimate of the device peak rate, measured in
 569          * [(sectors/usec) / 2^BFQ_RATE_SHIFT]. The left-shift by
 570          * BFQ_RATE_SHIFT is performed to increase precision in
 571          * fixed-point calculations.
 572          */
 573         u32 peak_rate;
 574
 575         /* maximum budget allotted to a bfq_queue before rescheduling */
 576         int bfq_max_budget;
 577
 578         /* list of all the bfq_queues active on the device */
 579         struct list_head active_list;
 580         /* list of all the bfq_queues idle on the device */
 581         struct list_head idle_list;
 582
 583         /*
 584          * Timeout for async/sync requests; when it fires, requests
 585          * are served in fifo order.
 586          */
 587         u64 bfq_fifo_expire[2];
 588         /* weight of backward seeks wrt forward ones */
 589         unsigned int bfq_back_penalty;
 590         /* maximum allowed backward seek */
 591         unsigned int bfq_back_max;
 592         /* maximum idling time */
 593         u32 bfq_slice_idle;
 594
 595         /* user-configured max budget value (0 for auto-tuning) */
 596         int bfq_user_max_budget;
 597         /*
 598          * Timeout for bfq_queues to consume their budget; used to
 599          * prevent seeky queues from imposing long latencies to
 600          * sequential or quasi-sequential ones (this also implies that
 601          * seeky queues cannot receive guarantees in the service
 602          * domain; after a timeout they are charged for the time they
 603          * have been in service, to preserve fairness among them, but
 604          * without service-domain guarantees).
 605          */
 606         unsigned int bfq_timeout;
 607
 608         /*
 609          * Number of consecutive requests that must be issued within
 610          * the idle time slice to set again idling to a queue which
 611          * was marked as non-I/O-bound (see the definition of the
 612          * IO_bound flag for further details).
 613          */
 614         unsigned int bfq_requests_within_timer;
 615
 616         /*
 617          * Force device idling whenever needed to provide accurate
 618          * service guarantees, without caring about throughput
 619          * issues. CAVEAT: this may even increase latencies, in case
 620          * of useless idling for processes that did stop doing I/O.
 621          */
 622         bool strict_guarantees;
 623
 624         /*
 625          * Last time at which a queue entered the current burst of
 626          * queues being activated shortly after each other; for more
 627          * details about this and the following parameters related to
 628          * a burst of activations, see the comments on the function
 629          * bfq_handle_burst.
 630          */
 631         unsigned long last_ins_in_burst;
 632         /*
 633          * Reference time interval used to decide whether a queue has
 634          * been activated shortly after @last_ins_in_burst.
 635          */
 636         unsigned long bfq_burst_interval;
 637         /* number of queues in the current burst of queue activations */
 638         int burst_size;
 639
 640         /* common parent entity for the queues in the burst */
 641         struct bfq_entity *burst_parent_entity;
 642         /* Maximum burst size above which the current queue-activation
 643          * burst is deemed as 'large'.
 644          */
 645         unsigned long bfq_large_burst_thresh;
 646         /* true if a large queue-activation burst is in progress */
 647         bool large_burst;
 648         /*
 649          * Head of the burst list (as for the above fields, more
 650          * details in the comments on the function bfq_handle_burst).
 651          */
 652         struct hlist_head burst_list;
 653
 654         /* if set to true, low-latency heuristics are enabled */
 655         bool low_latency;
 656         /*
 657          * Maximum factor by which the weight of a weight-raised queue
 658          * is multiplied.
 659          */
 660         unsigned int bfq_wr_coeff;
 661         /* maximum duration of a weight-raising period (jiffies) */
 662         unsigned int bfq_wr_max_time;
 663
 664         /* Maximum weight-raising duration for soft real-time processes */
 665         unsigned int bfq_wr_rt_max_time;
 666         /*
 667          * Minimum idle period after which weight-raising may be
 668          * reactivated for a queue (in jiffies).
 669          */
 670         unsigned int bfq_wr_min_idle_time;
 671         /*
 672          * Minimum period between request arrivals after which
 673          * weight-raising may be reactivated for an already busy async
 674          * queue (in jiffies).
 675          */
 676         unsigned long bfq_wr_min_inter_arr_async;
 677
 678         /* Max service-rate for a soft real-time queue, in sectors/sec */
 679         unsigned int bfq_wr_max_softrt_rate;
 680         /*
 681          * Cached value of the product ref_rate*ref_wr_duration, used
 682          * for computing the maximum duration of weight raising
 683          * automatically.
 684          */
 685         u64 rate_dur_prod;
 686
 687         /* fallback dummy bfqq for extreme OOM conditions */
 688         struct bfq_queue oom_bfqq;
 689
 690         spinlock_t lock;
 691
 692         /*
 693          * bic associated with the task issuing current bio for
 694          * merging. This and the next field are used as a support to
 695          * be able to perform the bic lookup, needed by bio-merge
 696          * functions, before the scheduler lock is taken, and thus
 697          * avoid taking the request-queue lock while the scheduler
 698          * lock is being held.
 699          */
 700         struct bfq_io_cq *bio_bic;
 701         /* bfqq associated with the task issuing current bio for merging */
 702         struct bfq_queue *bio_bfqq;
 703
 704         /*
 705          * Depth limits used in bfq_limit_depth (see comments on the
 706          * function)
 707          */
 708         unsigned int word_depths[2][2];
 709 };
 710
 711 enum bfqq_state_flags {
 712         BFQQF_just_created = 0, /* queue just allocated */
 713         BFQQF_busy,             /* has requests or is in service */
 714         BFQQF_wait_request,     /* waiting for a request */
 715         BFQQF_non_blocking_wait_rq, /*
 716                                      * waiting for a request
 717                                      * without idling the device
 718                                      */
 719         BFQQF_fifo_expire,      /* FIFO checked in this slice */
 720         BFQQF_has_short_ttime,  /* queue has a short think time */
 721         BFQQF_sync,             /* synchronous queue */
 722         BFQQF_IO_bound,         /*
 723                                  * bfqq has timed-out at least once
 724                                  * having consumed at most 2/10 of
 725                                  * its budget
 726                                  */
 727         BFQQF_in_large_burst,   /*
 728                                  * bfqq activated in a large burst,
 729                                  * see comments to bfq_handle_burst.
 730                                  */
 731         BFQQF_softrt_update,    /*
 732                                  * may need softrt-next-start
 733                                  * update
 734                                  */
 735         BFQQF_coop,             /* bfqq is shared */
 736         BFQQF_split_coop        /* shared bfqq will be split */
 737 };
 738
 739 #define BFQ_BFQQ_FNS(name)                                              \
 740 void bfq_mark_bfqq_##name(struct bfq_queue *bfqq);                      \
 741 void bfq_clear_bfqq_##name(struct bfq_queue *bfqq);                     \
 742 int bfq_bfqq_##name(const struct bfq_queue *bfqq);
 743
 744 BFQ_BFQQ_FNS(just_created);
 745 BFQ_BFQQ_FNS(busy);
 746 BFQ_BFQQ_FNS(wait_request);
 747 BFQ_BFQQ_FNS(non_blocking_wait_rq);
 748 BFQ_BFQQ_FNS(fifo_expire);
 749 BFQ_BFQQ_FNS(has_short_ttime);
 750 BFQ_BFQQ_FNS(sync);
 751 BFQ_BFQQ_FNS(IO_bound);
 752 BFQ_BFQQ_FNS(in_large_burst);
 753 BFQ_BFQQ_FNS(coop);
 754 BFQ_BFQQ_FNS(split_coop);
 755 BFQ_BFQQ_FNS(softrt_update);
 756 #undef BFQ_BFQQ_FNS
 757
 758 /* Expiration reasons. */
 759 enum bfqq_expiration {
 760         BFQQE_TOO_IDLE = 0,             /*
 761                                          * queue has been idling for
 762                                          * too long
 763                                          */
 764         BFQQE_BUDGET_TIMEOUT,   /* budget took too long to be used */
 765         BFQQE_BUDGET_EXHAUSTED, /* budget consumed */
 766         BFQQE_NO_MORE_REQUESTS, /* the queue has no more requests */
 767         BFQQE_PREEMPTED         /* preemption in progress */
 768 };
 769
 770 struct bfqg_stats {
 771 #if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
 772         /* number of ios merged */
 773         struct blkg_rwstat              merged;
 774         /* total time spent on device in ns, may not be accurate w/ queueing */
 775         struct blkg_rwstat              service_time;
 776         /* total time spent waiting in scheduler queue in ns */
 777         struct blkg_rwstat              wait_time;
 778         /* number of IOs queued up */
 779         struct blkg_rwstat              queued;
 780         /* total disk time and nr sectors dispatched by this group */
 781         struct blkg_stat                time;
 782         /* sum of number of ios queued across all samples */
 783         struct blkg_stat                avg_queue_size_sum;
 784         /* count of samples taken for average */
 785         struct blkg_stat                avg_queue_size_samples;
 786         /* how many times this group has been removed from service tree */
 787         struct blkg_stat                dequeue;
 788         /* total time spent waiting for it to be assigned a timeslice. */
 789         struct blkg_stat                group_wait_time;
 790         /* time spent idling for this blkcg_gq */
 791         struct blkg_stat                idle_time;
 792         /* total time with empty current active q with other requests queued */
 793         struct blkg_stat                empty_time;
 794         /* fields after this shouldn't be cleared on stat reset */
 795         u64                             start_group_wait_time;
 796         u64                             start_idle_time;
 797         u64                             start_empty_time;
 798         uint16_t                        flags;
 799 #endif  /* CONFIG_BFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
 800 };
 801
 802 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 803
 804 /*
 805  * struct bfq_group_data - per-blkcg storage for the blkio subsystem.
 806  *
 807  * @ps: @blkcg_policy_storage that this structure inherits
 808  * @weight: weight of the bfq_group
 809  */
 810 struct bfq_group_data {
 811         /* must be the first member */
 812         struct blkcg_policy_data pd;
 813
 814         unsigned int weight;
 815 };
 816
 817 /**
 818  * struct bfq_group - per (device, cgroup) data structure.
 819  * @entity: schedulable entity to insert into the parent group sched_data.
 820  * @sched_data: own sched_data, to contain child entities (they may be
 821  *              both bfq_queues and bfq_groups).
 822  * @bfqd: the bfq_data for the device this group acts upon.
 823  * @async_bfqq: array of async queues for all the tasks belonging to
 824  *              the group, one queue per ioprio value per ioprio_class,
 825  *              except for the idle class that has only one queue.
 826  * @async_idle_bfqq: async queue for the idle class (ioprio is ignored).
 827  * @my_entity: pointer to @entity, %NULL for the toplevel group; used
 828  *             to avoid too many special cases during group creation/
 829  *             migration.
 830  * @stats: stats for this bfqg.
 831  * @active_entities: number of active entities belonging to the group;
 832  *                   unused for the root group. Used to know whether there
 833  *                   are groups with more than one active @bfq_entity
 834  *                   (see the comments to the function
 835  *                   bfq_bfqq_may_idle()).
 836  * @rq_pos_tree: rbtree sorted by next_request position, used when
 837  *               determining if two or more queues have interleaving
 838  *               requests (see bfq_find_close_cooperator()).
 839  *
 840  * Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup
 841  * there is a set of bfq_groups, each one collecting the lower-level
 842  * entities belonging to the group that are acting on the same device.
 843  *
 844  * Locking works as follows:
 845  *    o @bfqd is protected by the queue lock, RCU is used to access it
 846  *      from the readers.
 847  *    o All the other fields are protected by the @bfqd queue lock.
 848  */
 849 struct bfq_group {
 850         /* must be the first member */
 851         struct blkg_policy_data pd;
 852
 853         /* cached path for this blkg (see comments in bfq_bic_update_cgroup) */
 854         char blkg_path[128];
 855
 856         /* reference counter (see comments in bfq_bic_update_cgroup) */
 857         int ref;
 858
 859         struct bfq_entity entity;
 860         struct bfq_sched_data sched_data;
 861
 862         void *bfqd;
 863
 864         struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
 865         struct bfq_queue *async_idle_bfqq;
 866
 867         struct bfq_entity *my_entity;
 868
 869         int active_entities;
 870
 871         struct rb_root rq_pos_tree;
 872
 873         struct bfqg_stats stats;
 874 };
 875
 876 #else
 877 struct bfq_group {
 878         struct bfq_sched_data sched_data;
 879
 880         struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
 881         struct bfq_queue *async_idle_bfqq;
 882
 883         struct rb_root rq_pos_tree;
 884 };
 885 #endif
 886
 887 struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
 888
 889 /* --------------- main algorithm interface ----------------- */
 890
 891 #define BFQ_SERVICE_TREE_INIT   ((struct bfq_service_tree)              \
 892                                 { RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
 893
 894 extern const int bfq_timeout;
 895
 896 struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync);
 897 void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync);
 898 struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic);
 899 void bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq);
 900 void bfq_weights_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 901                           struct rb_root *root);
 902 void __bfq_weights_tree_remove(struct bfq_data *bfqd,
 903                                struct bfq_queue *bfqq,
 904                                struct rb_root *root);
 905 void bfq_weights_tree_remove(struct bfq_data *bfqd,
 906                              struct bfq_queue *bfqq);
 907 void bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 908                      bool compensate, enum bfqq_expiration reason);
 909 void bfq_put_queue(struct bfq_queue *bfqq);
 910 void bfq_end_wr_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
 911 void bfq_schedule_dispatch(struct bfq_data *bfqd);
 912 void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
 913
 914 /* ------------ end of main algorithm interface -------------- */
 915
 916 /* ---------------- cgroups-support interface ---------------- */
 917
 918 void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
 919                               unsigned int op);
 920 void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op);
 921 void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op);
 922 void bfqg_stats_update_completion(struct bfq_group *bfqg, u64 start_time_ns,
 923                                   u64 io_start_time_ns, unsigned int op);
 924 void bfqg_stats_update_dequeue(struct bfq_group *bfqg);
 925 void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg);
 926 void bfqg_stats_update_idle_time(struct bfq_group *bfqg);
 927 void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg);
 928 void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg);
 929 void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 930                    struct bfq_group *bfqg);
 931
 932 void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg);
 933 void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio);
 934 void bfq_end_wr_async(struct bfq_data *bfqd);
 935 struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
 936                                      struct blkcg *blkcg);
 937 struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg);
 938 struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
 939 struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node);
 940 void bfqg_and_blkg_put(struct bfq_group *bfqg);
 941
 942 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 943 extern struct cftype bfq_blkcg_legacy_files[];
 944 extern struct cftype bfq_blkg_files[];
 945 extern struct blkcg_policy blkcg_policy_bfq;
 946 #endif
 947
 948 /* ------------- end of cgroups-support interface ------------- */
 949
 950 /* - interface of the internal hierarchical B-WF2Q+ scheduler - */
 951
 952 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 953 /* both next loops stop at one of the child entities of the root group */
 954 #define for_each_entity(entity) \
 955         for (; entity ; entity = entity->parent)
 956
 957 /*
 958  * For each iteration, compute parent in advance, so as to be safe if
 959  * entity is deallocated during the iteration. Such a deallocation may
 960  * happen as a consequence of a bfq_put_queue that frees the bfq_queue
 961  * containing entity.
 962  */
 963 #define for_each_entity_safe(entity, parent) \
 964         for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
 965
 966 #else /* CONFIG_BFQ_GROUP_IOSCHED */
 967 /*
 968  * Next two macros are fake loops when cgroups support is not
 969  * enabled. I fact, in such a case, there is only one level to go up
 970  * (to reach the root group).
 971  */
 972 #define for_each_entity(entity) \
 973         for (; entity ; entity = NULL)
 974
 975 #define for_each_entity_safe(entity, parent) \
 976         for (parent = NULL; entity ; entity = parent)
 977 #endif /* CONFIG_BFQ_GROUP_IOSCHED */
 978
 979 struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq);
 980 struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
 981 unsigned int bfq_tot_busy_queues(struct bfq_data *bfqd);
 982 struct bfq_service_tree *bfq_entity_service_tree(struct bfq_entity *entity);
 983 struct bfq_entity *bfq_entity_of(struct rb_node *node);
 984 unsigned short bfq_ioprio_to_weight(int ioprio);
 985 void bfq_put_idle_entity(struct bfq_service_tree *st,
 986                          struct bfq_entity *entity);
 987 struct bfq_service_tree *
 988 __bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
 989                                 struct bfq_entity *entity,
 990                                 bool update_class_too);
 991 void bfq_bfqq_served(struct bfq_queue *bfqq, int served);
 992 void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 993                           unsigned long time_ms);
 994 bool __bfq_deactivate_entity(struct bfq_entity *entity,
 995                              bool ins_into_idle_tree);
 996 bool next_queue_may_preempt(struct bfq_data *bfqd);
 997 struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd);
 998 bool __bfq_bfqd_reset_in_service(struct bfq_data *bfqd);
 999 void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1000                          bool ins_into_idle_tree, bool expiration);
1001 void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq);
1002 void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1003                       bool expiration);
1004 void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1005                        bool expiration);
1006 void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq);
1007
1008 /* --------------- end of interface of B-WF2Q+ ---------------- */
1009
1010 /* Logging facilities. */
1011 #ifdef CONFIG_BFQ_GROUP_IOSCHED
1012 struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
1013
1014 #define bfq_log_bfqq(bfqd, bfqq, fmt, args...)  do {                    \
1015         blk_add_cgroup_trace_msg((bfqd)->queue,                         \
1016                         bfqg_to_blkg(bfqq_group(bfqq))->blkcg,          \
1017                         "bfq%d%c " fmt, (bfqq)->pid,                    \
1018                         bfq_bfqq_sync((bfqq)) ? 'S' : 'A', ##args);     \
1019 } while (0)
1020
1021 #define bfq_log_bfqg(bfqd, bfqg, fmt, args...)  do {                    \
1022         blk_add_cgroup_trace_msg((bfqd)->queue,                         \
1023                 bfqg_to_blkg(bfqg)->blkcg, fmt, ##args);                \
1024 } while (0)
1025
1026 #else /* CONFIG_BFQ_GROUP_IOSCHED */
1027
1028 #define bfq_log_bfqq(bfqd, bfqq, fmt, args...)  \
1029         blk_add_trace_msg((bfqd)->queue, "bfq%d%c " fmt, (bfqq)->pid,   \
1030                         bfq_bfqq_sync((bfqq)) ? 'S' : 'A',              \
1031                                 ##args)
1032 #define bfq_log_bfqg(bfqd, bfqg, fmt, args...)          do {} while (0)
1033
1034 #endif /* CONFIG_BFQ_GROUP_IOSCHED */
1035
1036 #define bfq_log(bfqd, fmt, args...) \
1037         blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args)
1038
1039 #endif /* _BFQ_H */