block/bfq-iosched.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * Header file for the BFQ I/O scheduler: data structures and
   4  * prototypes of interface functions among BFQ components.
   5  */
   6 #ifndef _BFQ_H
   7 #define _BFQ_H
   8
   9 #include <linux/blktrace_api.h>
  10 #include <linux/hrtimer.h>
  11 #include <linux/blk-cgroup.h>
  12
  13 #define BFQ_IOPRIO_CLASSES      3
  14 #define BFQ_CL_IDLE_TIMEOUT     (HZ/5)
  15
  16 #define BFQ_MIN_WEIGHT                  1
  17 #define BFQ_MAX_WEIGHT                  1000
  18 #define BFQ_WEIGHT_CONVERSION_COEFF     10
  19
  20 #define BFQ_DEFAULT_QUEUE_IOPRIO        4
  21
  22 #define BFQ_WEIGHT_LEGACY_DFL   100
  23 #define BFQ_DEFAULT_GRP_IOPRIO  0
  24 #define BFQ_DEFAULT_GRP_CLASS   IOPRIO_CLASS_BE
  25
  26 #define MAX_PID_STR_LENGTH 12
  27
  28 /*
  29  * Soft real-time applications are extremely more latency sensitive
  30  * than interactive ones. Over-raise the weight of the former to
  31  * privilege them against the latter.
  32  */
  33 #define BFQ_SOFTRT_WEIGHT_FACTOR        100
  34
  35 struct bfq_entity;
  36
  37 /**
  38  * struct bfq_service_tree - per ioprio_class service tree.
  39  *
  40  * Each service tree represents a B-WF2Q+ scheduler on its own.  Each
  41  * ioprio_class has its own independent scheduler, and so its own
  42  * bfq_service_tree.  All the fields are protected by the queue lock
  43  * of the containing bfqd.
  44  */
  45 struct bfq_service_tree {
  46         /* tree for active entities (i.e., those backlogged) */
  47         struct rb_root active;
  48         /* tree for idle entities (i.e., not backlogged, with V < F_i)*/
  49         struct rb_root idle;
  50
  51         /* idle entity with minimum F_i */
  52         struct bfq_entity *first_idle;
  53         /* idle entity with maximum F_i */
  54         struct bfq_entity *last_idle;
  55
  56         /* scheduler virtual time */
  57         u64 vtime;
  58         /* scheduler weight sum; active and idle entities contribute to it */
  59         unsigned long wsum;
  60 };
  61
  62 /**
  63  * struct bfq_sched_data - multi-class scheduler.
  64  *
  65  * bfq_sched_data is the basic scheduler queue.  It supports three
  66  * ioprio_classes, and can be used either as a toplevel queue or as an
  67  * intermediate queue in a hierarchical setup.
  68  *
  69  * The supported ioprio_classes are the same as in CFQ, in descending
  70  * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE.
  71  * Requests from higher priority queues are served before all the
  72  * requests from lower priority queues; among requests of the same
  73  * queue requests are served according to B-WF2Q+.
  74  *
  75  * The schedule is implemented by the service trees, plus the field
  76  * @next_in_service, which points to the entity on the active trees
  77  * that will be served next, if 1) no changes in the schedule occurs
  78  * before the current in-service entity is expired, 2) the in-service
  79  * queue becomes idle when it expires, and 3) if the entity pointed by
  80  * in_service_entity is not a queue, then the in-service child entity
  81  * of the entity pointed by in_service_entity becomes idle on
  82  * expiration. This peculiar definition allows for the following
  83  * optimization, not yet exploited: while a given entity is still in
  84  * service, we already know which is the best candidate for next
  85  * service among the other active entities in the same parent
  86  * entity. We can then quickly compare the timestamps of the
  87  * in-service entity with those of such best candidate.
  88  *
  89  * All fields are protected by the lock of the containing bfqd.
  90  */
  91 struct bfq_sched_data {
  92         /* entity in service */
  93         struct bfq_entity *in_service_entity;
  94         /* head-of-line entity (see comments above) */
  95         struct bfq_entity *next_in_service;
  96         /* array of service trees, one per ioprio_class */
  97         struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES];
  98         /* last time CLASS_IDLE was served */
  99         unsigned long bfq_class_idle_last_service;
 100
 101 };
 102
 103 /**
 104  * struct bfq_weight_counter - counter of the number of all active queues
 105  *                             with a given weight.
 106  */
 107 struct bfq_weight_counter {
 108         unsigned int weight; /* weight of the queues this counter refers to */
 109         unsigned int num_active; /* nr of active queues with this weight */
 110         /*
 111          * Weights tree member (see bfq_data's @queue_weights_tree)
 112          */
 113         struct rb_node weights_node;
 114 };
 115
 116 /**
 117  * struct bfq_entity - schedulable entity.
 118  *
 119  * A bfq_entity is used to represent either a bfq_queue (leaf node in the
 120  * cgroup hierarchy) or a bfq_group into the upper level scheduler.  Each
 121  * entity belongs to the sched_data of the parent group in the cgroup
 122  * hierarchy.  Non-leaf entities have also their own sched_data, stored
 123  * in @my_sched_data.
 124  *
 125  * Each entity stores independently its priority values; this would
 126  * allow different weights on different devices, but this
 127  * functionality is not exported to userspace by now.  Priorities and
 128  * weights are updated lazily, first storing the new values into the
 129  * new_* fields, then setting the @prio_changed flag.  As soon as
 130  * there is a transition in the entity state that allows the priority
 131  * update to take place the effective and the requested priority
 132  * values are synchronized.
 133  *
 134  * Unless cgroups are used, the weight value is calculated from the
 135  * ioprio to export the same interface as CFQ.  When dealing with
 136  * "well-behaved" queues (i.e., queues that do not spend too much
 137  * time to consume their budget and have true sequential behavior, and
 138  * when there are no external factors breaking anticipation) the
 139  * relative weights at each level of the cgroups hierarchy should be
 140  * guaranteed.  All the fields are protected by the queue lock of the
 141  * containing bfqd.
 142  */
 143 struct bfq_entity {
 144         /* service_tree member */
 145         struct rb_node rb_node;
 146
 147         /*
 148          * Flag, true if the entity is on a tree (either the active or
 149          * the idle one of its service_tree) or is in service.
 150          */
 151         bool on_st;
 152
 153         /* B-WF2Q+ start and finish timestamps [sectors/weight] */
 154         u64 start, finish;
 155
 156         /* tree the entity is enqueued into; %NULL if not on a tree */
 157         struct rb_root *tree;
 158
 159         /*
 160          * minimum start time of the (active) subtree rooted at this
 161          * entity; used for O(log N) lookups into active trees
 162          */
 163         u64 min_start;
 164
 165         /* amount of service received during the last service slot */
 166         int service;
 167
 168         /* budget, used also to calculate F_i: F_i = S_i + @budget / @weight */
 169         int budget;
 170
 171         /* weight of the queue */
 172         int weight;
 173         /* next weight if a change is in progress */
 174         int new_weight;
 175
 176         /* original weight, used to implement weight boosting */
 177         int orig_weight;
 178
 179         /* parent entity, for hierarchical scheduling */
 180         struct bfq_entity *parent;
 181
 182         /*
 183          * For non-leaf nodes in the hierarchy, the associated
 184          * scheduler queue, %NULL on leaf nodes.
 185          */
 186         struct bfq_sched_data *my_sched_data;
 187         /* the scheduler queue this entity belongs to */
 188         struct bfq_sched_data *sched_data;
 189
 190         /* flag, set to request a weight, ioprio or ioprio_class change  */
 191         int prio_changed;
 192
 193         /* flag, set if the entity is counted in groups_with_pending_reqs */
 194         bool in_groups_with_pending_reqs;
 195 };
 196
 197 struct bfq_group;
 198
 199 /**
 200  * struct bfq_ttime - per process thinktime stats.
 201  */
 202 struct bfq_ttime {
 203         /* completion time of the last request */
 204         u64 last_end_request;
 205
 206         /* total process thinktime */
 207         u64 ttime_total;
 208         /* number of thinktime samples */
 209         unsigned long ttime_samples;
 210         /* average process thinktime */
 211         u64 ttime_mean;
 212 };
 213
 214 /**
 215  * struct bfq_queue - leaf schedulable entity.
 216  *
 217  * A bfq_queue is a leaf request queue; it can be associated with an
 218  * io_context or more, if it  is  async or shared  between  cooperating
 219  * processes. @cgroup holds a reference to the cgroup, to be sure that it
 220  * does not disappear while a bfqq still references it (mostly to avoid
 221  * races between request issuing and task migration followed by cgroup
 222  * destruction).
 223  * All the fields are protected by the queue lock of the containing bfqd.
 224  */
 225 struct bfq_queue {
 226         /* reference counter */
 227         int ref;
 228         /* parent bfq_data */
 229         struct bfq_data *bfqd;
 230
 231         /* current ioprio and ioprio class */
 232         unsigned short ioprio, ioprio_class;
 233         /* next ioprio and ioprio class if a change is in progress */
 234         unsigned short new_ioprio, new_ioprio_class;
 235
 236         /* last total-service-time sample, see bfq_update_inject_limit() */
 237         u64 last_serv_time_ns;
 238         /* limit for request injection */
 239         unsigned int inject_limit;
 240         /* last time the inject limit has been decreased, in jiffies */
 241         unsigned long decrease_time_jif;
 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         /*
 362          * Pointer to the waker queue for this queue, i.e., to the
 363          * queue Q such that this queue happens to get new I/O right
 364          * after some I/O request of Q is completed. For details, see
 365          * the comments on the choice of the queue for injection in
 366          * bfq_select_queue().
 367          */
 368         struct bfq_queue *waker_bfqq;
 369         /* node for woken_list, see below */
 370         struct hlist_node woken_list_node;
 371         /*
 372          * Head of the list of the woken queues for this queue, i.e.,
 373          * of the list of the queues for which this queue is a waker
 374          * queue. This list is used to reset the waker_bfqq pointer in
 375          * the woken queues when this queue exits.
 376          */
 377         struct hlist_head woken_list;
 378 };
 379
 380 /**
 381  * struct bfq_io_cq - per (request_queue, io_context) structure.
 382  */
 383 struct bfq_io_cq {
 384         /* associated io_cq structure */
 385         struct io_cq icq; /* must be the first member */
 386         /* array of two process queues, the sync and the async */
 387         struct bfq_queue *bfqq[2];
 388         /* per (request_queue, blkcg) ioprio */
 389         int ioprio;
 390 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 391         uint64_t blkcg_serial_nr; /* the current blkcg serial */
 392 #endif
 393         /*
 394          * Snapshot of the has_short_time flag before merging; taken
 395          * to remember its value while the queue is merged, so as to
 396          * be able to restore it in case of split.
 397          */
 398         bool saved_has_short_ttime;
 399         /*
 400          * Same purpose as the previous two fields for the I/O bound
 401          * classification of a queue.
 402          */
 403         bool saved_IO_bound;
 404
 405         /*
 406          * Same purpose as the previous fields for the value of the
 407          * field keeping the queue's belonging to a large burst
 408          */
 409         bool saved_in_large_burst;
 410         /*
 411          * True if the queue belonged to a burst list before its merge
 412          * with another cooperating queue.
 413          */
 414         bool was_in_burst_list;
 415
 416         /*
 417          * Save the weight when a merge occurs, to be able
 418          * to restore it in case of split. If the weight is not
 419          * correctly resumed when the queue is recycled,
 420          * then the weight of the recycled queue could differ
 421          * from the weight of the original queue.
 422          */
 423         unsigned int saved_weight;
 424
 425         /*
 426          * Similar to previous fields: save wr information.
 427          */
 428         unsigned long saved_wr_coeff;
 429         unsigned long saved_last_wr_start_finish;
 430         unsigned long saved_wr_start_at_switch_to_srt;
 431         unsigned int saved_wr_cur_max_time;
 432         struct bfq_ttime saved_ttime;
 433 };
 434
 435 /**
 436  * struct bfq_data - per-device data structure.
 437  *
 438  * All the fields are protected by @lock.
 439  */
 440 struct bfq_data {
 441         /* device request queue */
 442         struct request_queue *queue;
 443         /* dispatch queue */
 444         struct list_head dispatch;
 445
 446         /* root bfq_group for the device */
 447         struct bfq_group *root_group;
 448
 449         /*
 450          * rbtree of weight counters of @bfq_queues, sorted by
 451          * weight. Used to keep track of whether all @bfq_queues have
 452          * the same weight. The tree contains one counter for each
 453          * distinct weight associated to some active and not
 454          * weight-raised @bfq_queue (see the comments to the functions
 455          * bfq_weights_tree_[add|remove] for further details).
 456          */
 457         struct rb_root_cached queue_weights_tree;
 458
 459         /*
 460          * Number of groups with at least one descendant process that
 461          * has at least one request waiting for completion. Note that
 462          * this accounts for also requests already dispatched, but not
 463          * yet completed. Therefore this number of groups may differ
 464          * (be larger) than the number of active groups, as a group is
 465          * considered active only if its corresponding entity has
 466          * descendant queues with at least one request queued. This
 467          * number is used to decide whether a scenario is symmetric.
 468          * For a detailed explanation see comments on the computation
 469          * of the variable asymmetric_scenario in the function
 470          * bfq_better_to_idle().
 471          *
 472          * However, it is hard to compute this number exactly, for
 473          * groups with multiple descendant processes. Consider a group
 474          * that is inactive, i.e., that has no descendant process with
 475          * pending I/O inside BFQ queues. Then suppose that
 476          * num_groups_with_pending_reqs is still accounting for this
 477          * group, because the group has descendant processes with some
 478          * I/O request still in flight. num_groups_with_pending_reqs
 479          * should be decremented when the in-flight request of the
 480          * last descendant process is finally completed (assuming that
 481          * nothing else has changed for the group in the meantime, in
 482          * terms of composition of the group and active/inactive state of child
 483          * groups and processes). To accomplish this, an additional
 484          * pending-request counter must be added to entities, and must
 485          * be updated correctly. To avoid this additional field and operations,
 486          * we resort to the following tradeoff between simplicity and
 487          * accuracy: for an inactive group that is still counted in
 488          * num_groups_with_pending_reqs, we decrement
 489          * num_groups_with_pending_reqs when the first descendant
 490          * process of the group remains with no request waiting for
 491          * completion.
 492          *
 493          * Even this simpler decrement strategy requires a little
 494          * carefulness: to avoid multiple decrements, we flag a group,
 495          * more precisely an entity representing a group, as still
 496          * counted in num_groups_with_pending_reqs when it becomes
 497          * inactive. Then, when the first descendant queue of the
 498          * entity remains with no request waiting for completion,
 499          * num_groups_with_pending_reqs is decremented, and this flag
 500          * is reset. After this flag is reset for the entity,
 501          * num_groups_with_pending_reqs won't be decremented any
 502          * longer in case a new descendant queue of the entity remains
 503          * with no request waiting for completion.
 504          */
 505         unsigned int num_groups_with_pending_reqs;
 506
 507         /*
 508          * Per-class (RT, BE, IDLE) number of bfq_queues containing
 509          * requests (including the queue in service, even if it is
 510          * idling).
 511          */
 512         unsigned int busy_queues[3];
 513         /* number of weight-raised busy @bfq_queues */
 514         int wr_busy_queues;
 515         /* number of queued requests */
 516         int queued;
 517         /* number of requests dispatched and waiting for completion */
 518         int rq_in_driver;
 519
 520         /* true if the device is non rotational and performs queueing */
 521         bool nonrot_with_queueing;
 522
 523         /*
 524          * Maximum number of requests in driver in the last
 525          * @hw_tag_samples completed requests.
 526          */
 527         int max_rq_in_driver;
 528         /* number of samples used to calculate hw_tag */
 529         int hw_tag_samples;
 530         /* flag set to one if the driver is showing a queueing behavior */
 531         int hw_tag;
 532
 533         /* number of budgets assigned */
 534         int budgets_assigned;
 535
 536         /*
 537          * Timer set when idling (waiting) for the next request from
 538          * the queue in service.
 539          */
 540         struct hrtimer idle_slice_timer;
 541
 542         /* bfq_queue in service */
 543         struct bfq_queue *in_service_queue;
 544
 545         /* on-disk position of the last served request */
 546         sector_t last_position;
 547
 548         /* position of the last served request for the in-service queue */
 549         sector_t in_serv_last_pos;
 550
 551         /* time of last request completion (ns) */
 552         u64 last_completion;
 553
 554         /* bfqq owning the last completed rq */
 555         struct bfq_queue *last_completed_rq_bfqq;
 556
 557         /* time of last transition from empty to non-empty (ns) */
 558         u64 last_empty_occupied_ns;
 559
 560         /*
 561          * Flag set to activate the sampling of the total service time
 562          * of a just-arrived first I/O request (see
 563          * bfq_update_inject_limit()). This will cause the setting of
 564          * waited_rq when the request is finally dispatched.
 565          */
 566         bool wait_dispatch;
 567         /*
 568          *  If set, then bfq_update_inject_limit() is invoked when
 569          *  waited_rq is eventually completed.
 570          */
 571         struct request *waited_rq;
 572         /*
 573          * True if some request has been injected during the last service hole.
 574          */
 575         bool rqs_injected;
 576
 577         /* time of first rq dispatch in current observation interval (ns) */
 578         u64 first_dispatch;
 579         /* time of last rq dispatch in current observation interval (ns) */
 580         u64 last_dispatch;
 581
 582         /* beginning of the last budget */
 583         ktime_t last_budget_start;
 584         /* beginning of the last idle slice */
 585         ktime_t last_idling_start;
 586         unsigned long last_idling_start_jiffies;
 587
 588         /* number of samples in current observation interval */
 589         int peak_rate_samples;
 590         /* num of samples of seq dispatches in current observation interval */
 591         u32 sequential_samples;
 592         /* total num of sectors transferred in current observation interval */
 593         u64 tot_sectors_dispatched;
 594         /* max rq size seen during current observation interval (sectors) */
 595         u32 last_rq_max_size;
 596         /* time elapsed from first dispatch in current observ. interval (us) */
 597         u64 delta_from_first;
 598         /*
 599          * Current estimate of the device peak rate, measured in
 600          * [(sectors/usec) / 2^BFQ_RATE_SHIFT]. The left-shift by
 601          * BFQ_RATE_SHIFT is performed to increase precision in
 602          * fixed-point calculations.
 603          */
 604         u32 peak_rate;
 605
 606         /* maximum budget allotted to a bfq_queue before rescheduling */
 607         int bfq_max_budget;
 608
 609         /* list of all the bfq_queues active on the device */
 610         struct list_head active_list;
 611         /* list of all the bfq_queues idle on the device */
 612         struct list_head idle_list;
 613
 614         /*
 615          * Timeout for async/sync requests; when it fires, requests
 616          * are served in fifo order.
 617          */
 618         u64 bfq_fifo_expire[2];
 619         /* weight of backward seeks wrt forward ones */
 620         unsigned int bfq_back_penalty;
 621         /* maximum allowed backward seek */
 622         unsigned int bfq_back_max;
 623         /* maximum idling time */
 624         u32 bfq_slice_idle;
 625
 626         /* user-configured max budget value (0 for auto-tuning) */
 627         int bfq_user_max_budget;
 628         /*
 629          * Timeout for bfq_queues to consume their budget; used to
 630          * prevent seeky queues from imposing long latencies to
 631          * sequential or quasi-sequential ones (this also implies that
 632          * seeky queues cannot receive guarantees in the service
 633          * domain; after a timeout they are charged for the time they
 634          * have been in service, to preserve fairness among them, but
 635          * without service-domain guarantees).
 636          */
 637         unsigned int bfq_timeout;
 638
 639         /*
 640          * Number of consecutive requests that must be issued within
 641          * the idle time slice to set again idling to a queue which
 642          * was marked as non-I/O-bound (see the definition of the
 643          * IO_bound flag for further details).
 644          */
 645         unsigned int bfq_requests_within_timer;
 646
 647         /*
 648          * Force device idling whenever needed to provide accurate
 649          * service guarantees, without caring about throughput
 650          * issues. CAVEAT: this may even increase latencies, in case
 651          * of useless idling for processes that did stop doing I/O.
 652          */
 653         bool strict_guarantees;
 654
 655         /*
 656          * Last time at which a queue entered the current burst of
 657          * queues being activated shortly after each other; for more
 658          * details about this and the following parameters related to
 659          * a burst of activations, see the comments on the function
 660          * bfq_handle_burst.
 661          */
 662         unsigned long last_ins_in_burst;
 663         /*
 664          * Reference time interval used to decide whether a queue has
 665          * been activated shortly after @last_ins_in_burst.
 666          */
 667         unsigned long bfq_burst_interval;
 668         /* number of queues in the current burst of queue activations */
 669         int burst_size;
 670
 671         /* common parent entity for the queues in the burst */
 672         struct bfq_entity *burst_parent_entity;
 673         /* Maximum burst size above which the current queue-activation
 674          * burst is deemed as 'large'.
 675          */
 676         unsigned long bfq_large_burst_thresh;
 677         /* true if a large queue-activation burst is in progress */
 678         bool large_burst;
 679         /*
 680          * Head of the burst list (as for the above fields, more
 681          * details in the comments on the function bfq_handle_burst).
 682          */
 683         struct hlist_head burst_list;
 684
 685         /* if set to true, low-latency heuristics are enabled */
 686         bool low_latency;
 687         /*
 688          * Maximum factor by which the weight of a weight-raised queue
 689          * is multiplied.
 690          */
 691         unsigned int bfq_wr_coeff;
 692         /* maximum duration of a weight-raising period (jiffies) */
 693         unsigned int bfq_wr_max_time;
 694
 695         /* Maximum weight-raising duration for soft real-time processes */
 696         unsigned int bfq_wr_rt_max_time;
 697         /*
 698          * Minimum idle period after which weight-raising may be
 699          * reactivated for a queue (in jiffies).
 700          */
 701         unsigned int bfq_wr_min_idle_time;
 702         /*
 703          * Minimum period between request arrivals after which
 704          * weight-raising may be reactivated for an already busy async
 705          * queue (in jiffies).
 706          */
 707         unsigned long bfq_wr_min_inter_arr_async;
 708
 709         /* Max service-rate for a soft real-time queue, in sectors/sec */
 710         unsigned int bfq_wr_max_softrt_rate;
 711         /*
 712          * Cached value of the product ref_rate*ref_wr_duration, used
 713          * for computing the maximum duration of weight raising
 714          * automatically.
 715          */
 716         u64 rate_dur_prod;
 717
 718         /* fallback dummy bfqq for extreme OOM conditions */
 719         struct bfq_queue oom_bfqq;
 720
 721         spinlock_t lock;
 722
 723         /*
 724          * bic associated with the task issuing current bio for
 725          * merging. This and the next field are used as a support to
 726          * be able to perform the bic lookup, needed by bio-merge
 727          * functions, before the scheduler lock is taken, and thus
 728          * avoid taking the request-queue lock while the scheduler
 729          * lock is being held.
 730          */
 731         struct bfq_io_cq *bio_bic;
 732         /* bfqq associated with the task issuing current bio for merging */
 733         struct bfq_queue *bio_bfqq;
 734
 735         /*
 736          * Depth limits used in bfq_limit_depth (see comments on the
 737          * function)
 738          */
 739         unsigned int word_depths[2][2];
 740 };
 741
 742 enum bfqq_state_flags {
 743         BFQQF_just_created = 0, /* queue just allocated */
 744         BFQQF_busy,             /* has requests or is in service */
 745         BFQQF_wait_request,     /* waiting for a request */
 746         BFQQF_non_blocking_wait_rq, /*
 747                                      * waiting for a request
 748                                      * without idling the device
 749                                      */
 750         BFQQF_fifo_expire,      /* FIFO checked in this slice */
 751         BFQQF_has_short_ttime,  /* queue has a short think time */
 752         BFQQF_sync,             /* synchronous queue */
 753         BFQQF_IO_bound,         /*
 754                                  * bfqq has timed-out at least once
 755                                  * having consumed at most 2/10 of
 756                                  * its budget
 757                                  */
 758         BFQQF_in_large_burst,   /*
 759                                  * bfqq activated in a large burst,
 760                                  * see comments to bfq_handle_burst.
 761                                  */
 762         BFQQF_softrt_update,    /*
 763                                  * may need softrt-next-start
 764                                  * update
 765                                  */
 766         BFQQF_coop,             /* bfqq is shared */
 767         BFQQF_split_coop,       /* shared bfqq will be split */
 768         BFQQF_has_waker         /* bfqq has a waker queue */
 769 };
 770
 771 #define BFQ_BFQQ_FNS(name)                                              \
 772 void bfq_mark_bfqq_##name(struct bfq_queue *bfqq);                      \
 773 void bfq_clear_bfqq_##name(struct bfq_queue *bfqq);                     \
 774 int bfq_bfqq_##name(const struct bfq_queue *bfqq);
 775
 776 BFQ_BFQQ_FNS(just_created);
 777 BFQ_BFQQ_FNS(busy);
 778 BFQ_BFQQ_FNS(wait_request);
 779 BFQ_BFQQ_FNS(non_blocking_wait_rq);
 780 BFQ_BFQQ_FNS(fifo_expire);
 781 BFQ_BFQQ_FNS(has_short_ttime);
 782 BFQ_BFQQ_FNS(sync);
 783 BFQ_BFQQ_FNS(IO_bound);
 784 BFQ_BFQQ_FNS(in_large_burst);
 785 BFQ_BFQQ_FNS(coop);
 786 BFQ_BFQQ_FNS(split_coop);
 787 BFQ_BFQQ_FNS(softrt_update);
 788 BFQ_BFQQ_FNS(has_waker);
 789 #undef BFQ_BFQQ_FNS
 790
 791 /* Expiration reasons. */
 792 enum bfqq_expiration {
 793         BFQQE_TOO_IDLE = 0,             /*
 794                                          * queue has been idling for
 795                                          * too long
 796                                          */
 797         BFQQE_BUDGET_TIMEOUT,   /* budget took too long to be used */
 798         BFQQE_BUDGET_EXHAUSTED, /* budget consumed */
 799         BFQQE_NO_MORE_REQUESTS, /* the queue has no more requests */
 800         BFQQE_PREEMPTED         /* preemption in progress */
 801 };
 802
 803 struct bfq_stat {
 804         struct percpu_counter           cpu_cnt;
 805         atomic64_t                      aux_cnt;
 806 };
 807
 808 struct bfqg_stats {
 809 #ifdef CONFIG_BFQ_CGROUP_DEBUG
 810         /* number of ios merged */
 811         struct blkg_rwstat              merged;
 812         /* total time spent on device in ns, may not be accurate w/ queueing */
 813         struct blkg_rwstat              service_time;
 814         /* total time spent waiting in scheduler queue in ns */
 815         struct blkg_rwstat              wait_time;
 816         /* number of IOs queued up */
 817         struct blkg_rwstat              queued;
 818         /* total disk time and nr sectors dispatched by this group */
 819         struct bfq_stat         time;
 820         /* sum of number of ios queued across all samples */
 821         struct bfq_stat         avg_queue_size_sum;
 822         /* count of samples taken for average */
 823         struct bfq_stat         avg_queue_size_samples;
 824         /* how many times this group has been removed from service tree */
 825         struct bfq_stat         dequeue;
 826         /* total time spent waiting for it to be assigned a timeslice. */
 827         struct bfq_stat         group_wait_time;
 828         /* time spent idling for this blkcg_gq */
 829         struct bfq_stat         idle_time;
 830         /* total time with empty current active q with other requests queued */
 831         struct bfq_stat         empty_time;
 832         /* fields after this shouldn't be cleared on stat reset */
 833         u64                             start_group_wait_time;
 834         u64                             start_idle_time;
 835         u64                             start_empty_time;
 836         uint16_t                        flags;
 837 #endif /* CONFIG_BFQ_CGROUP_DEBUG */
 838 };
 839
 840 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 841
 842 /*
 843  * struct bfq_group_data - per-blkcg storage for the blkio subsystem.
 844  *
 845  * @ps: @blkcg_policy_storage that this structure inherits
 846  * @weight: weight of the bfq_group
 847  */
 848 struct bfq_group_data {
 849         /* must be the first member */
 850         struct blkcg_policy_data pd;
 851
 852         unsigned int weight;
 853 };
 854
 855 /**
 856  * struct bfq_group - per (device, cgroup) data structure.
 857  * @entity: schedulable entity to insert into the parent group sched_data.
 858  * @sched_data: own sched_data, to contain child entities (they may be
 859  *              both bfq_queues and bfq_groups).
 860  * @bfqd: the bfq_data for the device this group acts upon.
 861  * @async_bfqq: array of async queues for all the tasks belonging to
 862  *              the group, one queue per ioprio value per ioprio_class,
 863  *              except for the idle class that has only one queue.
 864  * @async_idle_bfqq: async queue for the idle class (ioprio is ignored).
 865  * @my_entity: pointer to @entity, %NULL for the toplevel group; used
 866  *             to avoid too many special cases during group creation/
 867  *             migration.
 868  * @stats: stats for this bfqg.
 869  * @active_entities: number of active entities belonging to the group;
 870  *                   unused for the root group. Used to know whether there
 871  *                   are groups with more than one active @bfq_entity
 872  *                   (see the comments to the function
 873  *                   bfq_bfqq_may_idle()).
 874  * @rq_pos_tree: rbtree sorted by next_request position, used when
 875  *               determining if two or more queues have interleaving
 876  *               requests (see bfq_find_close_cooperator()).
 877  *
 878  * Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup
 879  * there is a set of bfq_groups, each one collecting the lower-level
 880  * entities belonging to the group that are acting on the same device.
 881  *
 882  * Locking works as follows:
 883  *    o @bfqd is protected by the queue lock, RCU is used to access it
 884  *      from the readers.
 885  *    o All the other fields are protected by the @bfqd queue lock.
 886  */
 887 struct bfq_group {
 888         /* must be the first member */
 889         struct blkg_policy_data pd;
 890
 891         /* cached path for this blkg (see comments in bfq_bic_update_cgroup) */
 892         char blkg_path[128];
 893
 894         /* reference counter (see comments in bfq_bic_update_cgroup) */
 895         int ref;
 896
 897         struct bfq_entity entity;
 898         struct bfq_sched_data sched_data;
 899
 900         void *bfqd;
 901
 902         struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
 903         struct bfq_queue *async_idle_bfqq;
 904
 905         struct bfq_entity *my_entity;
 906
 907         int active_entities;
 908
 909         struct rb_root rq_pos_tree;
 910
 911         struct bfqg_stats stats;
 912 };
 913
 914 #else
 915 struct bfq_group {
 916         struct bfq_sched_data sched_data;
 917
 918         struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
 919         struct bfq_queue *async_idle_bfqq;
 920
 921         struct rb_root rq_pos_tree;
 922 };
 923 #endif
 924
 925 struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
 926
 927 /* --------------- main algorithm interface ----------------- */
 928
 929 #define BFQ_SERVICE_TREE_INIT   ((struct bfq_service_tree)              \
 930                                 { RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
 931
 932 extern const int bfq_timeout;
 933
 934 struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync);
 935 void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync);
 936 struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic);
 937 void bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq);
 938 void bfq_weights_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 939                           struct rb_root_cached *root);
 940 void __bfq_weights_tree_remove(struct bfq_data *bfqd,
 941                                struct bfq_queue *bfqq,
 942                                struct rb_root_cached *root);
 943 void bfq_weights_tree_remove(struct bfq_data *bfqd,
 944                              struct bfq_queue *bfqq);
 945 void bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 946                      bool compensate, enum bfqq_expiration reason);
 947 void bfq_put_queue(struct bfq_queue *bfqq);
 948 void bfq_end_wr_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
 949 void bfq_schedule_dispatch(struct bfq_data *bfqd);
 950 void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
 951
 952 /* ------------ end of main algorithm interface -------------- */
 953
 954 /* ---------------- cgroups-support interface ---------------- */
 955
 956 void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
 957                               unsigned int op);
 958 void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op);
 959 void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op);
 960 void bfqg_stats_update_completion(struct bfq_group *bfqg, u64 start_time_ns,
 961                                   u64 io_start_time_ns, unsigned int op);
 962 void bfqg_stats_update_dequeue(struct bfq_group *bfqg);
 963 void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg);
 964 void bfqg_stats_update_idle_time(struct bfq_group *bfqg);
 965 void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg);
 966 void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg);
 967 void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 968                    struct bfq_group *bfqg);
 969
 970 void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg);
 971 void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio);
 972 void bfq_end_wr_async(struct bfq_data *bfqd);
 973 struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
 974                                      struct blkcg *blkcg);
 975 struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg);
 976 struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
 977 struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node);
 978 void bfqg_and_blkg_put(struct bfq_group *bfqg);
 979
 980 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 981 extern struct cftype bfq_blkcg_legacy_files[];
 982 extern struct cftype bfq_blkg_files[];
 983 extern struct blkcg_policy blkcg_policy_bfq;
 984 #endif
 985
 986 /* ------------- end of cgroups-support interface ------------- */
 987
 988 /* - interface of the internal hierarchical B-WF2Q+ scheduler - */
 989
 990 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 991 /* both next loops stop at one of the child entities of the root group */
 992 #define for_each_entity(entity) \
 993         for (; entity ; entity = entity->parent)
 994
 995 /*
 996  * For each iteration, compute parent in advance, so as to be safe if
 997  * entity is deallocated during the iteration. Such a deallocation may
 998  * happen as a consequence of a bfq_put_queue that frees the bfq_queue
 999  * containing entity.
1000  */
1001 #define for_each_entity_safe(entity, parent) \
1002         for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
1003
1004 #else /* CONFIG_BFQ_GROUP_IOSCHED */
1005 /*
1006  * Next two macros are fake loops when cgroups support is not
1007  * enabled. I fact, in such a case, there is only one level to go up
1008  * (to reach the root group).
1009  */
1010 #define for_each_entity(entity) \
1011         for (; entity ; entity = NULL)
1012
1013 #define for_each_entity_safe(entity, parent) \
1014         for (parent = NULL; entity ; entity = parent)
1015 #endif /* CONFIG_BFQ_GROUP_IOSCHED */
1016
1017 struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq);
1018 struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
1019 unsigned int bfq_tot_busy_queues(struct bfq_data *bfqd);
1020 struct bfq_service_tree *bfq_entity_service_tree(struct bfq_entity *entity);
1021 struct bfq_entity *bfq_entity_of(struct rb_node *node);
1022 unsigned short bfq_ioprio_to_weight(int ioprio);
1023 void bfq_put_idle_entity(struct bfq_service_tree *st,
1024                          struct bfq_entity *entity);
1025 struct bfq_service_tree *
1026 __bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
1027                                 struct bfq_entity *entity,
1028                                 bool update_class_too);
1029 void bfq_bfqq_served(struct bfq_queue *bfqq, int served);
1030 void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1031                           unsigned long time_ms);
1032 bool __bfq_deactivate_entity(struct bfq_entity *entity,
1033                              bool ins_into_idle_tree);
1034 bool next_queue_may_preempt(struct bfq_data *bfqd);
1035 struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd);
1036 bool __bfq_bfqd_reset_in_service(struct bfq_data *bfqd);
1037 void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1038                          bool ins_into_idle_tree, bool expiration);
1039 void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq);
1040 void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1041                       bool expiration);
1042 void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1043                        bool expiration);
1044 void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq);
1045
1046 /* --------------- end of interface of B-WF2Q+ ---------------- */
1047
1048 /* Logging facilities. */
1049 static inline void bfq_pid_to_str(int pid, char *str, int len)
1050 {
1051         if (pid != -1)
1052                 snprintf(str, len, "%d", pid);
1053         else
1054                 snprintf(str, len, "SHARED-");
1055 }
1056
1057 #ifdef CONFIG_BFQ_GROUP_IOSCHED
1058 struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
1059
1060 #define bfq_log_bfqq(bfqd, bfqq, fmt, args...)  do {                    \
1061         char pid_str[MAX_PID_STR_LENGTH];       \
1062         bfq_pid_to_str((bfqq)->pid, pid_str, MAX_PID_STR_LENGTH);       \
1063         blk_add_cgroup_trace_msg((bfqd)->queue,                         \
1064                         bfqg_to_blkg(bfqq_group(bfqq))->blkcg,          \
1065                         "bfq%s%c " fmt, pid_str,                        \
1066                         bfq_bfqq_sync((bfqq)) ? 'S' : 'A', ##args);     \
1067 } while (0)
1068
1069 #define bfq_log_bfqg(bfqd, bfqg, fmt, args...)  do {                    \
1070         blk_add_cgroup_trace_msg((bfqd)->queue,                         \
1071                 bfqg_to_blkg(bfqg)->blkcg, fmt, ##args);                \
1072 } while (0)
1073
1074 #else /* CONFIG_BFQ_GROUP_IOSCHED */
1075
1076 #define bfq_log_bfqq(bfqd, bfqq, fmt, args...) do {     \
1077         char pid_str[MAX_PID_STR_LENGTH];       \
1078         bfq_pid_to_str((bfqq)->pid, pid_str, MAX_PID_STR_LENGTH);       \
1079         blk_add_trace_msg((bfqd)->queue, "bfq%s%c " fmt, pid_str,       \
1080                         bfq_bfqq_sync((bfqq)) ? 'S' : 'A',              \
1081                                 ##args);        \
1082 } while (0)
1083 #define bfq_log_bfqg(bfqd, bfqg, fmt, args...)          do {} while (0)
1084
1085 #endif /* CONFIG_BFQ_GROUP_IOSCHED */
1086
1087 #define bfq_log(bfqd, fmt, args...) \
1088         blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args)
1089
1090 #endif /* _BFQ_H */