block/bfq-iosched.h

Source file repositories/reference/linux-study-clean/block/bfq-iosched.h

File Facts

System
Linux kernel
Corpus path
block/bfq-iosched.h
Extension
.h
Size
41181 bytes
Lines
1203
Domain
Representative Device Path
Bucket
PCIe NVMe Storage Path
Inferred role
Representative Device Path: implementation source
Status
source implementation candidate

Why This File Exists

Part of the selected hardware vertical slice: PCI discovery, driver binding, NVMe queues, block requests, DMA, interrupts, and completion.

Dependency Surface

Detected Declarations

Annotated Snippet

struct bfq_service_tree {
	/* tree for active entities (i.e., those backlogged) */
	struct rb_root active;
	/* tree for idle entities (i.e., not backlogged, with V < F_i)*/
	struct rb_root idle;

	/* idle entity with minimum F_i */
	struct bfq_entity *first_idle;
	/* idle entity with maximum F_i */
	struct bfq_entity *last_idle;

	/* scheduler virtual time */
	u64 vtime;
	/* scheduler weight sum; active and idle entities contribute to it */
	unsigned long wsum;
};

/**
 * struct bfq_sched_data - multi-class scheduler.
 *
 * bfq_sched_data is the basic scheduler queue.  It supports three
 * ioprio_classes, and can be used either as a toplevel queue or as an
 * intermediate queue in a hierarchical setup.
 *
 * The supported ioprio_classes are the same as in CFQ, in descending
 * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE.
 * Requests from higher priority queues are served before all the
 * requests from lower priority queues; among requests of the same
 * queue requests are served according to B-WF2Q+.
 *
 * The schedule is implemented by the service trees, plus the field
 * @next_in_service, which points to the entity on the active trees
 * that will be served next, if 1) no changes in the schedule occurs
 * before the current in-service entity is expired, 2) the in-service
 * queue becomes idle when it expires, and 3) if the entity pointed by
 * in_service_entity is not a queue, then the in-service child entity
 * of the entity pointed by in_service_entity becomes idle on
 * expiration. This peculiar definition allows for the following
 * optimization, not yet exploited: while a given entity is still in
 * service, we already know which is the best candidate for next
 * service among the other active entities in the same parent
 * entity. We can then quickly compare the timestamps of the
 * in-service entity with those of such best candidate.
 *
 * All fields are protected by the lock of the containing bfqd.
 */
struct bfq_sched_data {
	/* entity in service */
	struct bfq_entity *in_service_entity;
	/* head-of-line entity (see comments above) */
	struct bfq_entity *next_in_service;
	/* array of service trees, one per ioprio_class */
	struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES];
	/* last time CLASS_IDLE was served */
	unsigned long bfq_class_idle_last_service;

};

/**
 * struct bfq_weight_counter - counter of the number of all active queues
 *                             with a given weight.
 */
struct bfq_weight_counter {
	unsigned int weight; /* weight of the queues this counter refers to */
	unsigned int num_active; /* nr of active queues with this weight */
	/*
	 * Weights tree member (see bfq_data's @queue_weights_tree)
	 */
	struct rb_node weights_node;
};

/**
 * struct bfq_entity - schedulable entity.
 *
 * A bfq_entity is used to represent either a bfq_queue (leaf node in the
 * cgroup hierarchy) or a bfq_group into the upper level scheduler.  Each
 * entity belongs to the sched_data of the parent group in the cgroup
 * hierarchy.  Non-leaf entities have also their own sched_data, stored
 * in @my_sched_data.
 *
 * Each entity stores independently its priority values; this would
 * allow different weights on different devices, but this
 * functionality is not exported to userspace by now.  Priorities and
 * weights are updated lazily, first storing the new values into the
 * new_* fields, then setting the @prio_changed flag.  As soon as
 * there is a transition in the entity state that allows the priority
 * update to take place the effective and the requested priority
 * values are synchronized.
 *
 * Unless cgroups are used, the weight value is calculated from the

Annotation

Implementation Notes