linux-6.12.1/block/bfq-iosched.h

1 /* SPDX-License-Identifier: GPL-2.0-or-later */
12 #include "blk-cgroup-rwstat.h"
29  * Soft real-time applications are extremely more latency sensitive
30  * than interactive ones. Over-raise the weight of the former to
38  * per-actuator data. The current value is hopefully a good upper
46  * struct bfq_service_tree - per ioprio_class service tree.
48  * Each service tree represents a B-WF2Q+ scheduler on its own.  Each
71  * struct bfq_sched_data - multi-class scheduler.
75  * intermediate queue in a hierarchical setup.
81  * queue requests are served according to B-WF2Q+.
86  * before the current in-service entity is expired, 2) the in-service
88  * in_service_entity is not a queue, then the in-service child entity
95  * in-service entity with those of such best candidate.
102 	/* head-of-line entity (see comments above) */
112  * struct bfq_weight_counter - counter of the number of all active queues
125  * struct bfq_entity - schedulable entity.
130  * hierarchy.  Non-leaf entities have also their own sched_data, stored
144  * "well-behaved" queues (i.e., queues that do not spend too much
161 	/* B-WF2Q+ start and finish timestamps [sectors/weight] */
182 	/* device weight, if non-zero, it overrides the default weight of
197 	 * For non-leaf nodes in the hierarchy, the associated
212 	/* last child queue of entity created (for non-leaf entities) */
219  * struct bfq_ttime - per process thinktime stats.
234  * struct bfq_queue - leaf schedulable entity.
259 	/* last total-service-time sample, see bfq_update_inject_limit() */
271 	/* request-position tree member (see bfq_group's @rq_pos_tree) */
273 	/* request-position tree root (see bfq_group's @rq_pos_tree) */
341 	/* current maximum weight-raising time for this queue */
347 	 * queue it is deemed as soft real-time (see the comments on
352 	 * Start time of the current weight-raising period if
353 	 * the @bfq-queue is being weight-raised, otherwise
354 	 * finish time of the last weight-raising period.
371 	 * last transition to weight-raised state.
415 * struct bfq_data - bfqq data unique and persistent for associated bfq_io_cq
475  * struct bfq_io_cq - per (request_queue, io_context) structure.
485 	 * the request is to be served by the j-th actuator of the
508  * struct bfq_data - per-device data structure.
526 	 * weight-raised @bfq_queue (see the comments to the functions
552 	 * should be decremented when the in-flight request of the
557 	 * pending-request counter must be added to entities, and must
582 	 * Per-class (RT, BE, IDLE) number of bfq_queues containing
587 	/* number of weight-raised busy @bfq_queues */
624 	/* on-disk position of the last served request */
627 	/* position of the last served request for the in-service queue */
630 	/* time of last request completion (ns) */
639 	/* time of last transition from empty to non-empty (ns) */
644 	 * of a just-arrived first I/O request (see
659 	/* time of first rq dispatch in current observation interval (ns) */
661 	/* time of last rq dispatch in current observation interval (ns) */
682 	 * [(sectors/usec) / 2^BFQ_RATE_SHIFT]. The left-shift by
684 	 * fixed-point calculations.
694 	 * per-actuator basis helps implementing per-actuator
713 	/* user-configured max budget value (0 for auto-tuning) */
718 	 * sequential or quasi-sequential ones (this also implies that
722 	 * without service-domain guarantees).
752 	/* Maximum burst size above which the current queue-activation
756 	/* true if a large queue-activation burst is in progress */
764 	/* if set to true, low-latency heuristics are enabled */
767 	 * Maximum factor by which the weight of a weight-raised queue
772 	/* Maximum weight-raising duration for soft real-time processes */
775 	 * Minimum idle period after which weight-raising may be
781 	 * weight-raising may be reactivated for an already busy async
786 	/* Max service-rate for a soft real-time queue, in sectors/sec */
790 	 * for computing the maximum duration of weight raising
803 	 * be able to perform the bic lookup, needed by bio-merge
805 	 * avoid taking the request-queue lock while the scheduler
821 	 * case of single-actuator drives.
837 	 * in-service queue does not contain I/O for that actuator,
841 	 * currently in-service queue.
846 	 * few drive-queue slots as possibile to the in-service
848 	 * that the service of I/O from the in-service bfq_queue gets
868 				 * bfqq has timed-out at least once
877 				 * may need softrt-next-start
927 	/* total time spent on device in ns, may not be accurate w/ queueing */
929 	/* total time spent waiting in scheduler queue in ns */
958  * struct bfq_group_data - per-blkcg storage for the blkio subsystem.
971  * struct bfq_group - per (device, cgroup) data structure.
994  * there is a set of bfq_groups, each one collecting the lower-level
1039 /* --------------- main algorithm interface ----------------- */
1063 /* ------------ end of main algorithm interface -------------- */
1065 /* ---------------- cgroups-support interface ---------------- */
1100 /* ------------- end of cgroups-support interface ------------- */
1102 /* - interface of the internal hierarchical B-WF2Q+ scheduler - */
1107 	for (; entity ; entity = entity->parent)
1116 	for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
1162 /* --------------- end of interface of B-WF2Q+ ---------------- */
1169 	if (bfqq->pid != -1)  in bfq_bfqq_name()
1170 		snprintf(str, len, "bfq%d%c", bfqq->pid, type);  in bfq_bfqq_name()
1172 		snprintf(str, len, "bfqSHARED-%c", type);  in bfq_bfqq_name()
1180 	if (likely(!blk_trace_note_message_enabled((bfqd)->queue)))	\
1183 	blk_add_cgroup_trace_msg((bfqd)->queue,				\
1184 			&bfqg_to_blkg(bfqq_group(bfqq))->blkcg->css,	\
1192 	if (likely(!blk_trace_note_message_enabled((bfqd)->queue)))	\
1195 	blk_add_trace_msg((bfqd)->queue, "%s " fmt, pid_str, ##args);	\
1201 	blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args)