linux-imx

/*

 * Header file for the BFQ I/O scheduler: data structures and

 * prototypes of interface functions among BFQ components.

 *

 *  This program is free software; you can redistribute it and/or

 *  modify it under the terms of the GNU General Public License as

 *  published by the Free Software Foundation; either version 2 of the

 *  License, or (at your option) any later version.

 *

 *  This program is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 *  General Public License for more details.

 */

#ifndef _BFQ_H

#define _BFQ_H

​

#include <linux/blktrace_api.h>

#include <linux/hrtimer.h>

#include <linux/blk-cgroup.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

​

/*

 * 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 entitities in the same parent