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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* Header file for the BFQ I/O scheduler: data structures and
* prototypes of interface functions among BFQ components.
*/
#ifndef _BFQ_H
#define _BFQ_H
#include <linux/blktrace_api.h>
#include <linux/hrtimer.h>
#include <linux/blk-cgroup.h>
#include "blk-cgroup-rwstat.h"
#define BFQ_IOPRIO_CLASSES 3
#define BFQ_CL_IDLE_TIMEOUT (HZ/5)
#define BFQ_MIN_WEIGHT 1
#define BFQ_MAX_WEIGHT 1000
#define BFQ_WEIGHT_CONVERSION_COEFF 10
#define BFQ_DEFAULT_QUEUE_IOPRIO 4
#define BFQ_WEIGHT_LEGACY_DFL 100
#define BFQ_DEFAULT_GRP_IOPRIO 0
#define BFQ_DEFAULT_GRP_CLASS IOPRIO_CLASS_BE
#define MAX_PID_STR_LENGTH 12
/*
* Soft real-time applications are extremely more latency sensitive
* than interactive ones. Over-raise the weight of the former to
* privilege them against the latter.
*/
#define BFQ_SOFTRT_WEIGHT_FACTOR 100
struct bfq_entity;
/**
* struct bfq_service_tree - per ioprio_class service tree.
*
* Each service tree represents a B-WF2Q+ scheduler on its own. Each
* ioprio_class has its own independent scheduler, and so its own
* bfq_service_tree. All the fields are protected by the queue lock
* of the containing bfqd.
*/
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
* ioprio to export the same interface as CFQ. When dealing with
* "well-behaved" queues (i.e., queues that do not spend too much
* time to consume their budget and have true sequential behavior, and
* when there are no external factors breaking anticipation) the
* relative weights at each level of the cgroups hierarchy should be
* guaranteed. All the fields are protected by the queue lock of the
* containing bfqd.
*/
struct bfq_entity {
/* service_tree member */
struct rb_node rb_node;
/*
* Flag, true if the entity is on a tree (either the active or
* the idle one of its service_tree) or is in service.
*/
bool on_st;
/* B-WF2Q+ start and finish timestamps [sectors/weight] */
u64 start, finish;
/* tree the entity is enqueued into; %NULL if not on a tree */
struct rb_root *tree;
/*
* minimum start time of the (active) subtree rooted at this
* entity; used for O(log N) lookups into active trees
*/
u64 min_start;
/* amount of service received during the last service slot */
int service;
/* budget, used also to calculate F_i: F_i = S_i + @budget / @weight */
int budget;
/* device weight, if non-zero, it overrides the default weight of
* bfq_group_data */
int dev_weight;
/* weight of the queue */
int weight;
/* next weight if a change is in progress */
int new_weight;
/* original weight, used to implement weight boosting */
int orig_weight;
/* parent entity, for hierarchical scheduling */
struct bfq_entity *parent;
/*
* For non-leaf nodes in the hierarchy, the associated
* scheduler queue, %NULL on leaf nodes.
*/
struct bfq_sched_data *my_sched_data;
/* the scheduler queue this entity belongs to */
struct bfq_sched_data *sched_data;
/* flag, set to request a weight, ioprio or ioprio_class change */
int prio_changed;
/* flag, set if the entity is counted in groups_with_pending_reqs */
bool in_groups_with_pending_reqs;
};
struct bfq_group;
/**
* struct bfq_ttime - per process thinktime stats.
*/
struct bfq_ttime {
/* completion time of the last request */
u64 last_end_request;
/* total process thinktime */
u64 ttime_total;
/* number of thinktime samples */
unsigned long ttime_samples;
/* average process thinktime */
u64 ttime_mean;
};
/**
* struct bfq_queue - leaf schedulable entity.
*
* A bfq_queue is a leaf request queue; it can be associated with an
* io_context or more, if it is async or shared between cooperating
* processes. @cgroup holds a reference to the cgroup, to be sure that it
* does not disappear while a bfqq still references it (mostly to avoid
* races between request issuing and task migration followed by cgroup
* destruction).
* All the fields are protected by the queue lock of the containing bfqd.
*/
struct bfq_queue {
/* reference counter */
int ref;
/* parent bfq_data */
struct bfq_data *bfqd;
/* current ioprio and ioprio class */
unsigned short ioprio,
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