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 #include "blk-cgroup-rwstat.h"
  14
  15 #define BFQ_IOPRIO_CLASSES      3
  16 #define BFQ_CL_IDLE_TIMEOUT     (HZ/5)
  17
  18 #define BFQ_MIN_WEIGHT                  1
  19 #define BFQ_MAX_WEIGHT                  1000
  20 #define BFQ_WEIGHT_CONVERSION_COEFF     10
  21
  22 #define BFQ_DEFAULT_QUEUE_IOPRIO        4
  23
  24 #define BFQ_WEIGHT_LEGACY_DFL   100
  25 #define BFQ_DEFAULT_GRP_IOPRIO  0
  26 #define BFQ_DEFAULT_GRP_CLASS   IOPRIO_CLASS_BE
  27
  28 #define MAX_PID_STR_LENGTH 12
  29
  30 /*
  31  * Soft real-time applications are extremely more latency sensitive
  32  * than interactive ones. Over-raise the weight of the former to
  33  * privilege them against the latter.
  34  */
  35 #define BFQ_SOFTRT_WEIGHT_FACTOR        100
  36
  37 struct bfq_entity;
  38
  39 /**
  40  * struct bfq_service_tree - per ioprio_class service tree.
  41  *
  42  * Each service tree represents a B-WF2Q+ scheduler on its own.  Each
  43  * ioprio_class has its own independent scheduler, and so its own
  44  * bfq_service_tree.  All the fields are protected by the queue lock
  45  * of the containing bfqd.
  46  */
  47 struct bfq_service_tree {
  48         /* tree for active entities (i.e., those backlogged) */
  49         struct rb_root active;
  50         /* tree for idle entities (i.e., not backlogged, with V < F_i)*/
  51         struct rb_root idle;
  52
  53         /* idle entity with minimum F_i */
  54         struct bfq_entity *first_idle;
  55         /* idle entity with maximum F_i */
  56         struct bfq_entity *last_idle;
  57
  58         /* scheduler virtual time */
  59         u64 vtime;
  60         /* scheduler weight sum; active and idle entities contribute to it */
  61         unsigned long wsum;
  62 };
  63
  64 /**
  65  * struct bfq_sched_data - multi-class scheduler.
  66  *
  67  * bfq_sched_data is the basic scheduler queue.  It supports three
  68  * ioprio_classes, and can be used either as a toplevel queue or as an
  69  * intermediate queue in a hierarchical setup.
  70  *
  71  * The supported ioprio_classes are the same as in CFQ, in descending
  72  * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE.
  73  * Requests from higher priority queues are served before all the
  74  * requests from lower priority queues; among requests of the same
  75  * queue requests are served according to B-WF2Q+.
  76  *
  77  * The schedule is implemented by the service trees, plus the field
  78  * @next_in_service, which points to the entity on the active trees
  79  * that will be served next, if 1) no changes in the schedule occurs
  80  * before the current in-service entity is expired, 2) the in-service
  81  * queue becomes idle when it expires, and 3) if the entity pointed by
  82  * in_service_entity is not a queue, then the in-service child entity
  83  * of the entity pointed by in_service_entity becomes idle on
  84  * expiration. This peculiar definition allows for the following
  85  * optimization, not yet exploited: while a given entity is still in
  86  * service, we already know which is the best candidate for next
  87  * service among the other active entities in the same parent
  88  * entity. We can then quickly compare the timestamps of the
  89  * in-service entity with those of such best candidate.
  90  *
  91  * All fields are protected by the lock of the containing bfqd.
  92  */
  93 struct bfq_sched_data {
  94         /* entity in service */
  95         struct bfq_entity *in_service_entity;
  96         /* head-of-line entity (see comments above) */
  97         struct bfq_entity *next_in_service;
  98         /* array of service trees, one per ioprio_class */
  99         struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES];
 100         /* last time CLASS_IDLE was served */
 101         unsigned long bfq_class_idle_last_service;
 102
 103 };
 104
 105 /**
 106  * struct bfq_weight_counter - counter of the number of all active queues
 107  *                             with a given weight.
 108  */
 109 struct bfq_weight_counter {
 110         unsigned int weight; /* weight of the queues this counter refers to */
 111         unsigned int num_active; /* nr of active queues with this weight */
 112         /*
 113          * Weights tree member (see bfq_data's @queue_weights_tree)
 114          */
 115         struct rb_node weights_node;
 116 };
 117
 118 /**
 119  * struct bfq_entity - schedulable entity.
 120  *
 121  * A bfq_entity is used to represent either a bfq_queue (leaf node in the
 122  * cgroup hierarchy) or a bfq_group into the upper level scheduler.  Each
 123  * entity belongs to the sched_data of the parent group in the cgroup
 124  * hierarchy.  Non-leaf entities have also their own sched_data, stored
 125  * in @my_sched_data.
 126  *
 127  * Each entity stores independently its priority values; this would
 128  * allow different weights on different devices, but this
 129  * functionality is not exported to userspace by now.  Priorities and
 130  * weights are updated lazily, first storing the new values into the
 131  * new_* fields, then setting the @prio_changed flag.  As soon as
 132  * there is a transition in the entity state that allows the priority
 133  * update to take place the effective and the requested priority
 134  * values are synchronized.
 135  *
 136  * Unless cgroups are used, the weight value is calculated from the
 137  * ioprio to export the same interface as CFQ.  When dealing with
 138  * "well-behaved" queues (i.e., queues that do not spend too much
 139  * time to consume their budget and have true sequential behavior, and
 140  * when there are no external factors breaking anticipation) the
 141  * relative weights at each level of the cgroups hierarchy should be
 142  * guaranteed.  All the fields are protected by the queue lock of the
 143  * containing bfqd.
 144  */
 145 struct bfq_entity {
 146         /* service_tree member */
 147         struct rb_node rb_node;
 148
 149         /*
 150          * Flag, true if the entity is on a tree (either the active or
 151          * the idle one of its service_tree) or is in service.
 152          */
 153         bool on_st_or_in_serv;
 154
 155         /* B-WF2Q+ start and finish timestamps [sectors/weight] */
 156         u64 start, finish;
 157
 158         /* tree the entity is enqueued into; %NULL if not on a tree */
 159         struct rb_root *tree;
 160
 161         /*
 162          * minimum start time of the (active) subtree rooted at this
 163          * entity; used for O(log N) lookups into active trees
 164          */
 165         u64 min_start;
 166
 167         /* amount of service received during the last service slot */
 168         int service;
 169
 170         /* budget, used also to calculate F_i: F_i = S_i + @budget / @weight */
 171         int budget;
 172
 173         /* device weight, if non-zero, it overrides the default weight of
 174          * bfq_group_data */
 175         int dev_weight;
 176         /* weight of the queue */
 177         int weight;
 178         /* next weight if a change is in progress */
 179         int new_weight;
 180
 181         /* original weight, used to implement weight boosting */
 182         int orig_weight;
 183
 184         /* parent entity, for hierarchical scheduling */
 185         struct bfq_entity *parent;
 186
 187         /*
 188          * For non-leaf nodes in the hierarchy, the associated
 189          * scheduler queue, %NULL on leaf nodes.
 190          */
 191         struct bfq_sched_data *my_sched_data;
 192         /* the scheduler queue this entity belongs to */
 193         struct bfq_sched_data *sched_data;
 194
 195         /* flag, set to request a weight, ioprio or ioprio_class change  */
 196         int prio_changed;
 197
 198         /* flag, set if the entity is counted in groups_with_pending_reqs */
 199         bool in_groups_with_pending_reqs;
 200 };
 201
 202 struct bfq_group;
 203
 204 /**
 205  * struct bfq_ttime - per process thinktime stats.
 206  */
 207 struct bfq_ttime {
 208         /* completion time of the last request */
 209         u64 last_end_request;
 210
 211         /* total process thinktime */
 212         u64 ttime_total;
 213         /* number of thinktime samples */
 214         unsigned long ttime_samples;
 215         /* average process thinktime */
 216         u64 ttime_mean;
 217 };
 218
 219 /**
 220  * struct bfq_queue - leaf schedulable entity.
 221  *
 222  * A bfq_queue is a leaf request queue; it can be associated with an
 223  * io_context or more, if it  is  async or shared  between  cooperating
 224  * processes. @cgroup holds a reference to the cgroup, to be sure that it
 225  * does not disappear while a bfqq still references it (mostly to avoid
 226  * races between request issuing and task migration followed by cgroup
 227  * destruction).
 228  * All the fields are protected by the queue lock of the containing bfqd.
 229  */
 230 struct bfq_queue {
 231         /* reference counter */
 232         int ref;
 233         /* parent bfq_data */
 234         struct bfq_data *bfqd;
 235
 236         /* current ioprio and ioprio class */
 237         unsigned short ioprio, ioprio_class;
 238         /* next ioprio and ioprio class if a change is in progress */
 239         unsigned short new_ioprio, new_ioprio_class;
 240
 241         /* last total-service-time sample, see bfq_update_inject_limit() */
 242         u64 last_serv_time_ns;
 243         /* limit for request injection */
 244         unsigned int inject_limit;
 245         /* last time the inject limit has been decreased, in jiffies */
 246         unsigned long decrease_time_jif;
 247
 248         /*
 249          * Shared bfq_queue if queue is cooperating with one or more
 250          * other queues.
 251          */
 252         struct bfq_queue *new_bfqq;
 253         /* request-position tree member (see bfq_group's @rq_pos_tree) */
 254         struct rb_node pos_node;
 255         /* request-position tree root (see bfq_group's @rq_pos_tree) */
 256         struct rb_root *pos_root;
 257
 258         /* sorted list of pending requests */
 259         struct rb_root sort_list;
 260         /* if fifo isn't expired, next request to serve */
 261         struct request *next_rq;
 262         /* number of sync and async requests queued */
 263         int queued[2];
 264         /* number of requests currently allocated */
 265         int allocated;
 266         /* number of pending metadata requests */
 267         int meta_pending;
 268         /* fifo list of requests in sort_list */
 269         struct list_head fifo;
 270
 271         /* entity representing this queue in the scheduler */
 272         struct bfq_entity entity;
 273
 274         /* pointer to the weight counter associated with this entity */
 275         struct bfq_weight_counter *weight_counter;
 276
 277         /* maximum budget allowed from the feedback mechanism */
 278         int max_budget;
 279         /* budget expiration (in jiffies) */
 280         unsigned long budget_timeout;
 281
 282         /* number of requests on the dispatch list or inside driver */
 283         int dispatched;
 284
 285         /* status flags */
 286         unsigned long flags;
 287
 288         /* node for active/idle bfqq list inside parent bfqd */
 289         struct list_head bfqq_list;
 290
 291         /* associated @bfq_ttime struct */
 292         struct bfq_ttime ttime;
 293
 294         /* bit vector: a 1 for each seeky requests in history */
 295         u32 seek_history;
 296
 297         /* node for the device's burst list */
 298         struct hlist_node burst_list_node;
 299
 300         /* position of the last request enqueued */
 301         sector_t last_request_pos;
 302
 303         /* Number of consecutive pairs of request completion and
 304          * arrival, such that the queue becomes idle after the
 305          * completion, but the next request arrives within an idle
 306          * time slice; used only if the queue's IO_bound flag has been
 307          * cleared.
 308          */
 309         unsigned int requests_within_timer;
 310
 311         /* pid of the process owning the queue, used for logging purposes */
 312         pid_t pid;
 313
 314         /*
 315          * Pointer to the bfq_io_cq owning the bfq_queue, set to %NULL
 316          * if the queue is shared.
 317          */
 318         struct bfq_io_cq *bic;
 319
 320         /* current maximum weight-raising time for this queue */
 321         unsigned long wr_cur_max_time;
 322         /*
 323          * Minimum time instant such that, only if a new request is
 324          * enqueued after this time instant in an idle @bfq_queue with
 325          * no outstanding requests, then the task associated with the
 326          * queue it is deemed as soft real-time (see the comments on
 327          * the function bfq_bfqq_softrt_next_start())
 328          */
 329         unsigned long soft_rt_next_start;
 330         /*
 331          * Start time of the current weight-raising period if
 332          * the @bfq-queue is being weight-raised, otherwise
 333          * finish time of the last weight-raising period.
 334          */
 335         unsigned long last_wr_start_finish;
 336         /* factor by which the weight of this queue is multiplied */
 337         unsigned int wr_coeff;
 338         /*
 339          * Time of the last transition of the @bfq_queue from idle to
 340          * backlogged.
 341          */
 342         unsigned long last_idle_bklogged;
 343         /*
 344          * Cumulative service received from the @bfq_queue since the
 345          * last transition from idle to backlogged.
 346          */
 347         unsigned long service_from_backlogged;
 348         /*
 349          * Cumulative service received from the @bfq_queue since its
 350          * last transition to weight-raised state.
 351          */
 352         unsigned long service_from_wr;
 353
 354         /*
 355          * Value of wr start time when switching to soft rt
 356          */
 357         unsigned long wr_start_at_switch_to_srt;
 358
 359         unsigned long split_time; /* time of last split */
 360
 361         unsigned long first_IO_time; /* time of first I/O for this queue */
 362
 363         /* max service rate measured so far */
 364         u32 max_service_rate;
 365
 366         /*
 367          * Pointer to the waker queue for this queue, i.e., to the
 368          * queue Q such that this queue happens to get new I/O right
 369          * after some I/O request of Q is completed. For details, see
 370          * the comments on the choice of the queue for injection in
 371          * bfq_select_queue().
 372          */
 373         struct bfq_queue *waker_bfqq;
 374         /* node for woken_list, see below */
 375         struct hlist_node woken_list_node;
 376         /*
 377          * Head of the list of the woken queues for this queue, i.e.,
 378          * of the list of the queues for which this queue is a waker
 379          * queue. This list is used to reset the waker_bfqq pointer in
 380          * the woken queues when this queue exits.
 381          */
 382         struct hlist_head woken_list;
 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          * Save the weight when a merge occurs, to be able
 423          * to restore it in case of split. If the weight is not
 424          * correctly resumed when the queue is recycled,
 425          * then the weight of the recycled queue could differ
 426          * from the weight of the original queue.
 427          */
 428         unsigned int saved_weight;
 429
 430         /*
 431          * Similar to previous fields: save wr information.
 432          */
 433         unsigned long saved_wr_coeff;
 434         unsigned long saved_last_wr_start_finish;
 435         unsigned long saved_wr_start_at_switch_to_srt;
 436         unsigned int saved_wr_cur_max_time;
 437         struct bfq_ttime saved_ttime;
 438 };
 439
 440 /**
 441  * struct bfq_data - per-device data structure.
 442  *
 443  * All the fields are protected by @lock.
 444  */
 445 struct bfq_data {
 446         /* device request queue */
 447         struct request_queue *queue;
 448         /* dispatch queue */
 449         struct list_head dispatch;
 450
 451         /* root bfq_group for the device */
 452         struct bfq_group *root_group;
 453
 454         /*
 455          * rbtree of weight counters of @bfq_queues, sorted by
 456          * weight. Used to keep track of whether all @bfq_queues have
 457          * the same weight. The tree contains one counter for each
 458          * distinct weight associated to some active and not
 459          * weight-raised @bfq_queue (see the comments to the functions
 460          * bfq_weights_tree_[add|remove] for further details).
 461          */
 462         struct rb_root_cached queue_weights_tree;
 463
 464         /*
 465          * Number of groups with at least one descendant process that
 466          * has at least one request waiting for completion. Note that
 467          * this accounts for also requests already dispatched, but not
 468          * yet completed. Therefore this number of groups may differ
 469          * (be larger) than the number of active groups, as a group is
 470          * considered active only if its corresponding entity has
 471          * descendant queues with at least one request queued. This
 472          * number is used to decide whether a scenario is symmetric.
 473          * For a detailed explanation see comments on the computation
 474          * of the variable asymmetric_scenario in the function
 475          * bfq_better_to_idle().
 476          *
 477          * However, it is hard to compute this number exactly, for
 478          * groups with multiple descendant processes. Consider a group
 479          * that is inactive, i.e., that has no descendant process with
 480          * pending I/O inside BFQ queues. Then suppose that
 481          * num_groups_with_pending_reqs is still accounting for this
 482          * group, because the group has descendant processes with some
 483          * I/O request still in flight. num_groups_with_pending_reqs
 484          * should be decremented when the in-flight request of the
 485          * last descendant process is finally completed (assuming that
 486          * nothing else has changed for the group in the meantime, in
 487          * terms of composition of the group and active/inactive state of child
 488          * groups and processes). To accomplish this, an additional
 489          * pending-request counter must be added to entities, and must
 490          * be updated correctly. To avoid this additional field and operations,
 491          * we resort to the following tradeoff between simplicity and
 492          * accuracy: for an inactive group that is still counted in
 493          * num_groups_with_pending_reqs, we decrement
 494          * num_groups_with_pending_reqs when the first descendant
 495          * process of the group remains with no request waiting for
 496          * completion.
 497          *
 498          * Even this simpler decrement strategy requires a little
 499          * carefulness: to avoid multiple decrements, we flag a group,
 500          * more precisely an entity representing a group, as still
 501          * counted in num_groups_with_pending_reqs when it becomes
 502          * inactive. Then, when the first descendant queue of the
 503          * entity remains with no request waiting for completion,
 504          * num_groups_with_pending_reqs is decremented, and this flag
 505          * is reset. After this flag is reset for the entity,
 506          * num_groups_with_pending_reqs won't be decremented any
 507          * longer in case a new descendant queue of the entity remains
 508          * with no request waiting for completion.
 509          */
 510         unsigned int num_groups_with_pending_reqs;
 511
 512         /*
 513          * Per-class (RT, BE, IDLE) number of bfq_queues containing
 514          * requests (including the queue in service, even if it is
 515          * idling).
 516          */
 517         unsigned int busy_queues[3];
 518         /* number of weight-raised busy @bfq_queues */
 519         int wr_busy_queues;
 520         /* number of queued requests */
 521         int queued;
 522         /* number of requests dispatched and waiting for completion */
 523         int rq_in_driver;
 524
 525         /* true if the device is non rotational and performs queueing */
 526         bool nonrot_with_queueing;
 527
 528         /*
 529          * Maximum number of requests in driver in the last
 530          * @hw_tag_samples completed requests.
 531          */
 532         int max_rq_in_driver;
 533         /* number of samples used to calculate hw_tag */
 534         int hw_tag_samples;
 535         /* flag set to one if the driver is showing a queueing behavior */
 536         int hw_tag;
 537
 538         /* number of budgets assigned */
 539         int budgets_assigned;
 540
 541         /*
 542          * Timer set when idling (waiting) for the next request from
 543          * the queue in service.
 544          */
 545         struct hrtimer idle_slice_timer;
 546
 547         /* bfq_queue in service */
 548         struct bfq_queue *in_service_queue;
 549
 550         /* on-disk position of the last served request */
 551         sector_t last_position;
 552
 553         /* position of the last served request for the in-service queue */
 554         sector_t in_serv_last_pos;
 555
 556         /* time of last request completion (ns) */
 557         u64 last_completion;
 558
 559         /* bfqq owning the last completed rq */
 560         struct bfq_queue *last_completed_rq_bfqq;
 561
 562         /* time of last transition from empty to non-empty (ns) */
 563         u64 last_empty_occupied_ns;
 564
 565         /*
 566          * Flag set to activate the sampling of the total service time
 567          * of a just-arrived first I/O request (see
 568          * bfq_update_inject_limit()). This will cause the setting of
 569          * waited_rq when the request is finally dispatched.
 570          */
 571         bool wait_dispatch;
 572         /*
 573          *  If set, then bfq_update_inject_limit() is invoked when
 574          *  waited_rq is eventually completed.
 575          */
 576         struct request *waited_rq;
 577         /*
 578          * True if some request has been injected during the last service hole.
 579          */
 580         bool rqs_injected;
 581
 582         /* time of first rq dispatch in current observation interval (ns) */
 583         u64 first_dispatch;
 584         /* time of last rq dispatch in current observation interval (ns) */
 585         u64 last_dispatch;
 586
 587         /* beginning of the last budget */
 588         ktime_t last_budget_start;
 589         /* beginning of the last idle slice */
 590         ktime_t last_idling_start;
 591         unsigned long last_idling_start_jiffies;
 592
 593         /* number of samples in current observation interval */
 594         int peak_rate_samples;
 595         /* num of samples of seq dispatches in current observation interval */
 596         u32 sequential_samples;
 597         /* total num of sectors transferred in current observation interval */
 598         u64 tot_sectors_dispatched;
 599         /* max rq size seen during current observation interval (sectors) */
 600         u32 last_rq_max_size;
 601         /* time elapsed from first dispatch in current observ. interval (us) */
 602         u64 delta_from_first;
 603         /*
 604          * Current estimate of the device peak rate, measured in
 605          * [(sectors/usec) / 2^BFQ_RATE_SHIFT]. The left-shift by
 606          * BFQ_RATE_SHIFT is performed to increase precision in
 607          * fixed-point calculations.
 608          */
 609         u32 peak_rate;
 610
 611         /* maximum budget allotted to a bfq_queue before rescheduling */
 612         int bfq_max_budget;
 613
 614         /* list of all the bfq_queues active on the device */
 615         struct list_head active_list;
 616         /* list of all the bfq_queues idle on the device */
 617         struct list_head idle_list;
 618
 619         /*
 620          * Timeout for async/sync requests; when it fires, requests
 621          * are served in fifo order.
 622          */
 623         u64 bfq_fifo_expire[2];
 624         /* weight of backward seeks wrt forward ones */
 625         unsigned int bfq_back_penalty;
 626         /* maximum allowed backward seek */
 627         unsigned int bfq_back_max;
 628         /* maximum idling time */
 629         u32 bfq_slice_idle;
 630
 631         /* user-configured max budget value (0 for auto-tuning) */
 632         int bfq_user_max_budget;
 633         /*
 634          * Timeout for bfq_queues to consume their budget; used to
 635          * prevent seeky queues from imposing long latencies to
 636          * sequential or quasi-sequential ones (this also implies that
 637          * seeky queues cannot receive guarantees in the service
 638          * domain; after a timeout they are charged for the time they
 639          * have been in service, to preserve fairness among them, but
 640          * without service-domain guarantees).
 641          */
 642         unsigned int bfq_timeout;
 643
 644         /*
 645          * Number of consecutive requests that must be issued within
 646          * the idle time slice to set again idling to a queue which
 647          * was marked as non-I/O-bound (see the definition of the
 648          * IO_bound flag for further details).
 649          */
 650         unsigned int bfq_requests_within_timer;
 651
 652         /*
 653          * Force device idling whenever needed to provide accurate
 654          * service guarantees, without caring about throughput
 655          * issues. CAVEAT: this may even increase latencies, in case
 656          * of useless idling for processes that did stop doing I/O.
 657          */
 658         bool strict_guarantees;
 659
 660         /*
 661          * Last time at which a queue entered the current burst of
 662          * queues being activated shortly after each other; for more
 663          * details about this and the following parameters related to
 664          * a burst of activations, see the comments on the function
 665          * bfq_handle_burst.
 666          */
 667         unsigned long last_ins_in_burst;
 668         /*
 669          * Reference time interval used to decide whether a queue has
 670          * been activated shortly after @last_ins_in_burst.
 671          */
 672         unsigned long bfq_burst_interval;
 673         /* number of queues in the current burst of queue activations */
 674         int burst_size;
 675
 676         /* common parent entity for the queues in the burst */
 677         struct bfq_entity *burst_parent_entity;
 678         /* Maximum burst size above which the current queue-activation
 679          * burst is deemed as 'large'.
 680          */
 681         unsigned long bfq_large_burst_thresh;
 682         /* true if a large queue-activation burst is in progress */
 683         bool large_burst;
 684         /*
 685          * Head of the burst list (as for the above fields, more
 686          * details in the comments on the function bfq_handle_burst).
 687          */
 688         struct hlist_head burst_list;
 689
 690         /* if set to true, low-latency heuristics are enabled */
 691         bool low_latency;
 692         /*
 693          * Maximum factor by which the weight of a weight-raised queue
 694          * is multiplied.
 695          */
 696         unsigned int bfq_wr_coeff;
 697         /* maximum duration of a weight-raising period (jiffies) */
 698         unsigned int bfq_wr_max_time;
 699
 700         /* Maximum weight-raising duration for soft real-time processes */
 701         unsigned int bfq_wr_rt_max_time;
 702         /*
 703          * Minimum idle period after which weight-raising may be
 704          * reactivated for a queue (in jiffies).
 705          */
 706         unsigned int bfq_wr_min_idle_time;
 707         /*
 708          * Minimum period between request arrivals after which
 709          * weight-raising may be reactivated for an already busy async
 710          * queue (in jiffies).
 711          */
 712         unsigned long bfq_wr_min_inter_arr_async;
 713
 714         /* Max service-rate for a soft real-time queue, in sectors/sec */
 715         unsigned int bfq_wr_max_softrt_rate;
 716         /*
 717          * Cached value of the product ref_rate*ref_wr_duration, used
 718          * for computing the maximum duration of weight raising
 719          * automatically.
 720          */
 721         u64 rate_dur_prod;
 722
 723         /* fallback dummy bfqq for extreme OOM conditions */
 724         struct bfq_queue oom_bfqq;
 725
 726         spinlock_t lock;
 727
 728         /*
 729          * bic associated with the task issuing current bio for
 730          * merging. This and the next field are used as a support to
 731          * be able to perform the bic lookup, needed by bio-merge
 732          * functions, before the scheduler lock is taken, and thus
 733          * avoid taking the request-queue lock while the scheduler
 734          * lock is being held.
 735          */
 736         struct bfq_io_cq *bio_bic;
 737         /* bfqq associated with the task issuing current bio for merging */
 738         struct bfq_queue *bio_bfqq;
 739
 740         /*
 741          * Depth limits used in bfq_limit_depth (see comments on the
 742          * function)
 743          */
 744         unsigned int word_depths[2][2];
 745 };
 746
 747 enum bfqq_state_flags {
 748         BFQQF_just_created = 0, /* queue just allocated */
 749         BFQQF_busy,             /* has requests or is in service */
 750         BFQQF_wait_request,     /* waiting for a request */
 751         BFQQF_non_blocking_wait_rq, /*
 752                                      * waiting for a request
 753                                      * without idling the device
 754                                      */
 755         BFQQF_fifo_expire,      /* FIFO checked in this slice */
 756         BFQQF_has_short_ttime,  /* queue has a short think time */
 757         BFQQF_sync,             /* synchronous queue */
 758         BFQQF_IO_bound,         /*
 759                                  * bfqq has timed-out at least once
 760                                  * having consumed at most 2/10 of
 761                                  * its budget
 762                                  */
 763         BFQQF_in_large_burst,   /*
 764                                  * bfqq activated in a large burst,
 765                                  * see comments to bfq_handle_burst.
 766                                  */
 767         BFQQF_softrt_update,    /*
 768                                  * may need softrt-next-start
 769                                  * update
 770                                  */
 771         BFQQF_coop,             /* bfqq is shared */
 772         BFQQF_split_coop,       /* shared bfqq will be split */
 773         BFQQF_has_waker         /* bfqq has a waker queue */
 774 };
 775
 776 #define BFQ_BFQQ_FNS(name)                                              \
 777 void bfq_mark_bfqq_##name(struct bfq_queue *bfqq);                      \
 778 void bfq_clear_bfqq_##name(struct bfq_queue *bfqq);                     \
 779 int bfq_bfqq_##name(const struct bfq_queue *bfqq);
 780
 781 BFQ_BFQQ_FNS(just_created);
 782 BFQ_BFQQ_FNS(busy);
 783 BFQ_BFQQ_FNS(wait_request);
 784 BFQ_BFQQ_FNS(non_blocking_wait_rq);
 785 BFQ_BFQQ_FNS(fifo_expire);
 786 BFQ_BFQQ_FNS(has_short_ttime);
 787 BFQ_BFQQ_FNS(sync);
 788 BFQ_BFQQ_FNS(IO_bound);
 789 BFQ_BFQQ_FNS(in_large_burst);
 790 BFQ_BFQQ_FNS(coop);
 791 BFQ_BFQQ_FNS(split_coop);
 792 BFQ_BFQQ_FNS(softrt_update);
 793 BFQ_BFQQ_FNS(has_waker);
 794 #undef BFQ_BFQQ_FNS
 795
 796 /* Expiration reasons. */
 797 enum bfqq_expiration {
 798         BFQQE_TOO_IDLE = 0,             /*
 799                                          * queue has been idling for
 800                                          * too long
 801                                          */
 802         BFQQE_BUDGET_TIMEOUT,   /* budget took too long to be used */
 803         BFQQE_BUDGET_EXHAUSTED, /* budget consumed */
 804         BFQQE_NO_MORE_REQUESTS, /* the queue has no more requests */
 805         BFQQE_PREEMPTED         /* preemption in progress */
 806 };
 807
 808 struct bfq_stat {
 809         struct percpu_counter           cpu_cnt;
 810         atomic64_t                      aux_cnt;
 811 };
 812
 813 struct bfqg_stats {
 814         /* basic stats */
 815         struct blkg_rwstat              bytes;
 816         struct blkg_rwstat              ios;
 817 #ifdef CONFIG_BFQ_CGROUP_DEBUG
 818         /* number of ios merged */
 819         struct blkg_rwstat              merged;
 820         /* total time spent on device in ns, may not be accurate w/ queueing */
 821         struct blkg_rwstat              service_time;
 822         /* total time spent waiting in scheduler queue in ns */
 823         struct blkg_rwstat              wait_time;
 824         /* number of IOs queued up */
 825         struct blkg_rwstat              queued;
 826         /* total disk time and nr sectors dispatched by this group */
 827         struct bfq_stat         time;
 828         /* sum of number of ios queued across all samples */
 829         struct bfq_stat         avg_queue_size_sum;
 830         /* count of samples taken for average */
 831         struct bfq_stat         avg_queue_size_samples;
 832         /* how many times this group has been removed from service tree */
 833         struct bfq_stat         dequeue;
 834         /* total time spent waiting for it to be assigned a timeslice. */
 835         struct bfq_stat         group_wait_time;
 836         /* time spent idling for this blkcg_gq */
 837         struct bfq_stat         idle_time;
 838         /* total time with empty current active q with other requests queued */
 839         struct bfq_stat         empty_time;
 840         /* fields after this shouldn't be cleared on stat reset */
 841         u64                             start_group_wait_time;
 842         u64                             start_idle_time;
 843         u64                             start_empty_time;
 844         uint16_t                        flags;
 845 #endif /* CONFIG_BFQ_CGROUP_DEBUG */
 846 };
 847
 848 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 849
 850 /*
 851  * struct bfq_group_data - per-blkcg storage for the blkio subsystem.
 852  *
 853  * @ps: @blkcg_policy_storage that this structure inherits
 854  * @weight: weight of the bfq_group
 855  */
 856 struct bfq_group_data {
 857         /* must be the first member */
 858         struct blkcg_policy_data pd;
 859
 860         unsigned int weight;
 861 };
 862
 863 /**
 864  * struct bfq_group - per (device, cgroup) data structure.
 865  * @entity: schedulable entity to insert into the parent group sched_data.
 866  * @sched_data: own sched_data, to contain child entities (they may be
 867  *              both bfq_queues and bfq_groups).
 868  * @bfqd: the bfq_data for the device this group acts upon.
 869  * @async_bfqq: array of async queues for all the tasks belonging to
 870  *              the group, one queue per ioprio value per ioprio_class,
 871  *              except for the idle class that has only one queue.
 872  * @async_idle_bfqq: async queue for the idle class (ioprio is ignored).
 873  * @my_entity: pointer to @entity, %NULL for the toplevel group; used
 874  *             to avoid too many special cases during group creation/
 875  *             migration.
 876  * @stats: stats for this bfqg.
 877  * @active_entities: number of active entities belonging to the group;
 878  *                   unused for the root group. Used to know whether there
 879  *                   are groups with more than one active @bfq_entity
 880  *                   (see the comments to the function
 881  *                   bfq_bfqq_may_idle()).
 882  * @rq_pos_tree: rbtree sorted by next_request position, used when
 883  *               determining if two or more queues have interleaving
 884  *               requests (see bfq_find_close_cooperator()).
 885  *
 886  * Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup
 887  * there is a set of bfq_groups, each one collecting the lower-level
 888  * entities belonging to the group that are acting on the same device.
 889  *
 890  * Locking works as follows:
 891  *    o @bfqd is protected by the queue lock, RCU is used to access it
 892  *      from the readers.
 893  *    o All the other fields are protected by the @bfqd queue lock.
 894  */
 895 struct bfq_group {
 896         /* must be the first member */
 897         struct blkg_policy_data pd;
 898
 899         /* cached path for this blkg (see comments in bfq_bic_update_cgroup) */
 900         char blkg_path[128];
 901
 902         /* reference counter (see comments in bfq_bic_update_cgroup) */
 903         int ref;
 904
 905         struct bfq_entity entity;
 906         struct bfq_sched_data sched_data;
 907
 908         void *bfqd;
 909
 910         struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
 911         struct bfq_queue *async_idle_bfqq;
 912
 913         struct bfq_entity *my_entity;
 914
 915         int active_entities;
 916
 917         struct rb_root rq_pos_tree;
 918
 919         struct bfqg_stats stats;
 920 };
 921
 922 #else
 923 struct bfq_group {
 924         struct bfq_entity entity;
 925         struct bfq_sched_data sched_data;
 926
 927         struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
 928         struct bfq_queue *async_idle_bfqq;
 929
 930         struct rb_root rq_pos_tree;
 931 };
 932 #endif
 933
 934 struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
 935
 936 /* --------------- main algorithm interface ----------------- */
 937
 938 #define BFQ_SERVICE_TREE_INIT   ((struct bfq_service_tree)              \
 939                                 { RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
 940
 941 extern const int bfq_timeout;
 942
 943 struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync);
 944 void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync);
 945 struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic);
 946 void bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq);
 947 void bfq_weights_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 948                           struct rb_root_cached *root);
 949 void __bfq_weights_tree_remove(struct bfq_data *bfqd,
 950                                struct bfq_queue *bfqq,
 951                                struct rb_root_cached *root);
 952 void bfq_weights_tree_remove(struct bfq_data *bfqd,
 953                              struct bfq_queue *bfqq);
 954 void bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 955                      bool compensate, enum bfqq_expiration reason);
 956 void bfq_put_queue(struct bfq_queue *bfqq);
 957 void bfq_end_wr_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
 958 void bfq_release_process_ref(struct bfq_data *bfqd, struct bfq_queue *bfqq);
 959 void bfq_schedule_dispatch(struct bfq_data *bfqd);
 960 void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
 961
 962 /* ------------ end of main algorithm interface -------------- */
 963
 964 /* ---------------- cgroups-support interface ---------------- */
 965
 966 void bfqg_stats_update_legacy_io(struct request_queue *q, struct request *rq);
 967 void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
 968                               unsigned int op);
 969 void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op);
 970 void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op);
 971 void bfqg_stats_update_completion(struct bfq_group *bfqg, u64 start_time_ns,
 972                                   u64 io_start_time_ns, unsigned int op);
 973 void bfqg_stats_update_dequeue(struct bfq_group *bfqg);
 974 void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg);
 975 void bfqg_stats_update_idle_time(struct bfq_group *bfqg);
 976 void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg);
 977 void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg);
 978 void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 979                    struct bfq_group *bfqg);
 980
 981 void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg);
 982 void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio);
 983 void bfq_end_wr_async(struct bfq_data *bfqd);
 984 struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
 985                                      struct blkcg *blkcg);
 986 struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg);
 987 struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
 988 struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node);
 989 void bfqg_and_blkg_put(struct bfq_group *bfqg);
 990
 991 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 992 extern struct cftype bfq_blkcg_legacy_files[];
 993 extern struct cftype bfq_blkg_files[];
 994 extern struct blkcg_policy blkcg_policy_bfq;
 995 #endif
 996
 997 /* ------------- end of cgroups-support interface ------------- */
 998
 999 /* - interface of the internal hierarchical B-WF2Q+ scheduler - */
1000
1001 #ifdef CONFIG_BFQ_GROUP_IOSCHED
1002 /* both next loops stop at one of the child entities of the root group */
1003 #define for_each_entity(entity) \
1004         for (; entity ; entity = entity->parent)
1005
1006 /*
1007  * For each iteration, compute parent in advance, so as to be safe if
1008  * entity is deallocated during the iteration. Such a deallocation may
1009  * happen as a consequence of a bfq_put_queue that frees the bfq_queue
1010  * containing entity.
1011  */
1012 #define for_each_entity_safe(entity, parent) \
1013         for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
1014
1015 #else /* CONFIG_BFQ_GROUP_IOSCHED */
1016 /*
1017  * Next two macros are fake loops when cgroups support is not
1018  * enabled. I fact, in such a case, there is only one level to go up
1019  * (to reach the root group).
1020  */
1021 #define for_each_entity(entity) \
1022         for (; entity ; entity = NULL)
1023
1024 #define for_each_entity_safe(entity, parent) \
1025         for (parent = NULL; entity ; entity = parent)
1026 #endif /* CONFIG_BFQ_GROUP_IOSCHED */
1027
1028 struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq);
1029 struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
1030 unsigned int bfq_tot_busy_queues(struct bfq_data *bfqd);
1031 struct bfq_service_tree *bfq_entity_service_tree(struct bfq_entity *entity);
1032 struct bfq_entity *bfq_entity_of(struct rb_node *node);
1033 unsigned short bfq_ioprio_to_weight(int ioprio);
1034 void bfq_put_idle_entity(struct bfq_service_tree *st,
1035                          struct bfq_entity *entity);
1036 struct bfq_service_tree *
1037 __bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
1038                                 struct bfq_entity *entity,
1039                                 bool update_class_too);
1040 void bfq_bfqq_served(struct bfq_queue *bfqq, int served);
1041 void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1042                           unsigned long time_ms);
1043 bool __bfq_deactivate_entity(struct bfq_entity *entity,
1044                              bool ins_into_idle_tree);
1045 bool next_queue_may_preempt(struct bfq_data *bfqd);
1046 struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd);
1047 bool __bfq_bfqd_reset_in_service(struct bfq_data *bfqd);
1048 void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1049                          bool ins_into_idle_tree, bool expiration);
1050 void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq);
1051 void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1052                       bool expiration);
1053 void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1054                        bool expiration);
1055 void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq);
1056
1057 /* --------------- end of interface of B-WF2Q+ ---------------- */
1058
1059 /* Logging facilities. */
1060 static inline void bfq_pid_to_str(int pid, char *str, int len)
1061 {
1062         if (pid != -1)
1063                 snprintf(str, len, "%d", pid);
1064         else
1065                 snprintf(str, len, "SHARED-");
1066 }
1067
1068 #ifdef CONFIG_BFQ_GROUP_IOSCHED
1069 struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
1070
1071 #define bfq_log_bfqq(bfqd, bfqq, fmt, args...)  do {                    \
1072         char pid_str[MAX_PID_STR_LENGTH];       \
1073         if (likely(!blk_trace_note_message_enabled((bfqd)->queue)))     \
1074                 break;                                                  \
1075         bfq_pid_to_str((bfqq)->pid, pid_str, MAX_PID_STR_LENGTH);       \
1076         blk_add_cgroup_trace_msg((bfqd)->queue,                         \
1077                         bfqg_to_blkg(bfqq_group(bfqq))->blkcg,          \
1078                         "bfq%s%c " fmt, pid_str,                        \
1079                         bfq_bfqq_sync((bfqq)) ? 'S' : 'A', ##args);     \
1080 } while (0)
1081
1082 #define bfq_log_bfqg(bfqd, bfqg, fmt, args...)  do {                    \
1083         blk_add_cgroup_trace_msg((bfqd)->queue,                         \
1084                 bfqg_to_blkg(bfqg)->blkcg, fmt, ##args);                \
1085 } while (0)
1086
1087 #else /* CONFIG_BFQ_GROUP_IOSCHED */
1088
1089 #define bfq_log_bfqq(bfqd, bfqq, fmt, args...) do {     \
1090         char pid_str[MAX_PID_STR_LENGTH];       \
1091         if (likely(!blk_trace_note_message_enabled((bfqd)->queue)))     \
1092                 break;                                                  \
1093         bfq_pid_to_str((bfqq)->pid, pid_str, MAX_PID_STR_LENGTH);       \
1094         blk_add_trace_msg((bfqd)->queue, "bfq%s%c " fmt, pid_str,       \
1095                         bfq_bfqq_sync((bfqq)) ? 'S' : 'A',              \
1096                                 ##args);        \
1097 } while (0)
1098 #define bfq_log_bfqg(bfqd, bfqg, fmt, args...)          do {} while (0)
1099
1100 #endif /* CONFIG_BFQ_GROUP_IOSCHED */
1101
1102 #define bfq_log(bfqd, fmt, args...) \
1103         blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args)
1104
1105 #endif /* _BFQ_H */