linux-imx

/*

 * The Kyber I/O scheduler. Controls latency by throttling queue depths using

 * scalable techniques.

 *

 * Copyright (C) 2017 Facebook

 *

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

 * modify it under the terms of the GNU General Public

 * License v2 as published by the Free Software Foundation.

 *

 * 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.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <https://www.gnu.org/licenses/>.

 */

​

#include <linux/kernel.h>

#include <linux/blkdev.h>

#include <linux/blk-mq.h>

#include <linux/elevator.h>

#include <linux/module.h>

#include <linux/sbitmap.h>

​

#include "blk.h"

#include "blk-mq.h"

#include "blk-mq-debugfs.h"

#include "blk-mq-sched.h"

#include "blk-mq-tag.h"

​

#define CREATE_TRACE_POINTS

#include <trace/events/kyber.h>

​

/*

 * Scheduling domains: the device is divided into multiple domains based on the

 * request type.

 */

enum {

    KYBER_READ,

    KYBER_WRITE,

    KYBER_DISCARD,

    KYBER_OTHER,

    KYBER_NUM_DOMAINS,

};

​

static const char *kyber_domain_names[] = {

    [KYBER_READ] = "READ",

    [KYBER_WRITE] = "WRITE",

    [KYBER_DISCARD] = "DISCARD",

    [KYBER_OTHER] = "OTHER",

};

​

enum {

    /*

     * In order to prevent starvation of synchronous requests by a flood of

     * asynchronous requests, we reserve 25% of requests for synchronous

     * operations.

     */

    KYBER_ASYNC_PERCENT = 75,

};

​