fs/zfs/vdev_queue.c

	vdev_queue.c revision fa9e4066f08beec538e775443c5be79dd423fcab
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/zfs_context.h>
#include <sys/spa.h>
#include <sys/vdev_impl.h>
#include <sys/zio.h>
#include <sys/avl.h>

/*
 * Virtual device vector for disk I/O scheduling.
 */
int
vdev_queue_deadline_compare(const void *x1, const void *x2)
{
    const zio_t *z1 = x1;
    const zio_t *z2 = x2;

    if (z1->io_deadline < z2->io_deadline)
        return (-1);
    if (z1->io_deadline > z2->io_deadline)
        return (1);

    if (z1->io_offset < z2->io_offset)
        return (-1);
    if (z1->io_offset > z2->io_offset)
        return (1);

    if (z1 < z2)
        return (-1);
    if (z1 > z2)
        return (1);

    return (0);
}

int
vdev_queue_offset_compare(const void *x1, const void *x2)
{
    const zio_t *z1 = x1;
    const zio_t *z2 = x2;

    if (z1->io_offset < z2->io_offset)
        return (-1);
    if (z1->io_offset > z2->io_offset)
        return (1);

    if (z1 < z2)
        return (-1);
    if (z1 > z2)
        return (1);

    return (0);
}

void
vdev_queue_init(vdev_t *vd)
{
    vdev_queue_t *vq = &vd->vdev_queue;

    mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);

    avl_create(&vq->vq_deadline_tree, vdev_queue_deadline_compare,
        sizeof (zio_t), offsetof(struct zio, io_deadline_node));

    avl_create(&vq->vq_read_tree, vdev_queue_offset_compare,
        sizeof (zio_t), offsetof(struct zio, io_offset_node));

    avl_create(&vq->vq_write_tree, vdev_queue_offset_compare,
        sizeof (zio_t), offsetof(struct zio, io_offset_node));

    avl_create(&vq->vq_pending_tree, vdev_queue_offset_compare,
        sizeof (zio_t), offsetof(struct zio, io_offset_node));
}

void
vdev_queue_fini(vdev_t *vd)
{
    vdev_queue_t *vq = &vd->vdev_queue;

    avl_destroy(&vq->vq_deadline_tree);
    avl_destroy(&vq->vq_read_tree);
    avl_destroy(&vq->vq_write_tree);
    avl_destroy(&vq->vq_pending_tree);

    mutex_destroy(&vq->vq_lock);
}

static void
vdev_queue_agg_io_done(zio_t *aio)
{
    zio_t *dio;
    uint64_t offset = 0;

    while ((dio = aio->io_delegate_list) != NULL) {
        if (aio->io_type == ZIO_TYPE_READ)
            bcopy((char *)aio->io_data + offset, dio->io_data,
                dio->io_size);
        offset += dio->io_size;
        aio->io_delegate_list = dio->io_delegate_next;
        dio->io_delegate_next = NULL;
        dio->io_error = aio->io_error;
        zio_next_stage(dio);
    }
    ASSERT3U(offset, ==, aio->io_size);

    zio_buf_free(aio->io_data, aio->io_size);
}

#define IS_ADJACENT(io, nio) \
    ((io)->io_offset + (io)->io_size == (nio)->io_offset)

typedef void zio_issue_func_t(zio_t *);

static zio_t *
vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit,
    zio_issue_func_t **funcp)
{
    zio_t *fio, *lio, *aio, *dio;
    avl_tree_t *tree;
    uint64_t size;

    ASSERT(MUTEX_HELD(&vq->vq_lock));

    *funcp = NULL;

    if (avl_numnodes(&vq->vq_pending_tree) >= pending_limit ||
        avl_numnodes(&vq->vq_deadline_tree) == 0)
        return (NULL);

    fio = lio = avl_first(&vq->vq_deadline_tree);

    tree = fio->io_vdev_tree;
    size = fio->io_size;

    while ((dio = AVL_PREV(tree, fio)) != NULL && IS_ADJACENT(dio, fio) &&
        size + dio->io_size <= vq->vq_agg_limit) {
        dio->io_delegate_next = fio;
        fio = dio;
        size += dio->io_size;
    }

    while ((dio = AVL_NEXT(tree, lio)) != NULL && IS_ADJACENT(lio, dio) &&
        size + dio->io_size <= vq->vq_agg_limit) {
        lio->io_delegate_next = dio;
        lio = dio;
        size += dio->io_size;
    }

    if (fio != lio) {
        char *buf = zio_buf_alloc(size);
        uint64_t offset = 0;
        int nagg = 0;

        ASSERT(size <= vq->vq_agg_limit);

        aio = zio_vdev_child_io(fio, NULL, fio->io_vd,
            fio->io_offset, buf, size, fio->io_type,
            ZIO_PRIORITY_NOW, ZIO_FLAG_DONT_QUEUE |
            ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_PROPAGATE,
            vdev_queue_agg_io_done, NULL);

        aio->io_delegate_list = fio;

        for (dio = fio; dio != NULL; dio = dio->io_delegate_next) {
            ASSERT(dio->io_type == aio->io_type);
            if (dio->io_type == ZIO_TYPE_WRITE)
                bcopy(dio->io_data, buf + offset, dio->io_size);
            offset += dio->io_size;
            avl_remove(&vq->vq_deadline_tree, dio);
            avl_remove(tree, dio);
            zio_vdev_io_bypass(dio);
            nagg++;
        }

        ASSERT(offset == size);

        dprintf("%5s  T=%llu  off=%8llx  agg=%3d  "
            "old=%5llx  new=%5llx\n",
            zio_type_name[fio->io_type],
            fio->io_deadline, fio->io_offset, nagg, fio->io_size, size);

        avl_add(&vq->vq_pending_tree, aio);

        *funcp = zio_nowait;
        return (aio);
    }

    avl_remove(&vq->vq_deadline_tree, fio);
    avl_remove(tree, fio);

    avl_add(&vq->vq_pending_tree, fio);

    *funcp = zio_next_stage;

    return (fio);
}

zio_t *
vdev_queue_io(zio_t *zio)
{
    vdev_queue_t *vq = &zio->io_vd->vdev_queue;
    zio_t *nio;
    zio_issue_func_t *func;

    ASSERT(zio->io_type == ZIO_TYPE_READ || zio->io_type == ZIO_TYPE_WRITE);

    if (zio->io_flags & ZIO_FLAG_DONT_QUEUE)
        return (zio);

    zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE;

    if (zio->io_type == ZIO_TYPE_READ)
        zio->io_vdev_tree = &vq->vq_read_tree;
    else
        zio->io_vdev_tree = &vq->vq_write_tree;

    mutex_enter(&vq->vq_lock);

    zio->io_deadline = (zio->io_timestamp >> vq->vq_time_shift) +
        zio->io_priority;

    avl_add(&vq->vq_deadline_tree, zio);
    avl_add(zio->io_vdev_tree, zio);

    nio = vdev_queue_io_to_issue(vq, vq->vq_min_pending, &func);

    mutex_exit(&vq->vq_lock);

    if (nio == NULL || func != zio_nowait)
        return (nio);

    func(nio);
    return (NULL);
}

void
vdev_queue_io_done(zio_t *zio)
{
    vdev_queue_t *vq = &zio->io_vd->vdev_queue;
    zio_t *nio;
    zio_issue_func_t *func;
    int i;

    mutex_enter(&vq->vq_lock);

    avl_remove(&vq->vq_pending_tree, zio);

    for (i = 0; i < vq->vq_ramp_rate; i++) {
        nio = vdev_queue_io_to_issue(vq, vq->vq_max_pending, &func);
        if (nio == NULL)
            break;
        mutex_exit(&vq->vq_lock);
        if (func == zio_next_stage)
            zio_vdev_io_reissue(nio);
        func(nio);
        mutex_enter(&vq->vq_lock);
    }

    mutex_exit(&vq->vq_lock);
}