Commit 6953d920 authored by Denis V. Lunev's avatar Denis V. Lunev Committed by Stefan Hajnoczi
Browse files

block/parallels: improve image reading performance 



Try to perform IO for the biggest continuous block possible.
The performance for sequential read is increased from 220 Mb/sec to
360 Mb/sec for continous image on my SSD HDD.

Signed-off-by: default avatarDenis V. Lunev <den@openvz.org>
Reviewed-by: default avatarRoman Kagan <rkagan@parallels.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarRoman Kagan <rkagan@parallels.com>
Message-id: 1430207220-24458-23-git-send-email-den@openvz.org
CC: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent a6be831e

block/parallels.c

+31 −5
Original line number Diff line number Diff line
@@ -103,6 +103,35 @@ static int cluster_remainder(BDRVParallelsState *s, int64_t sector_num, 
    return MIN(nb_sectors, ret);

}



static int64_t block_status(BDRVParallelsState *s, int64_t sector_num,

                            int nb_sectors, int *pnum)

{

    int64_t start_off = -2, prev_end_off = -2;



    *pnum = 0;

    while (nb_sectors > 0 || start_off == -2) {

        int64_t offset = seek_to_sector(s, sector_num);

        int to_end;



        if (start_off == -2) {

            start_off = offset;

            prev_end_off = offset;

        } else if (offset != prev_end_off) {

            break;

        }



        to_end = cluster_remainder(s, sector_num, nb_sectors);

        nb_sectors -= to_end;

        sector_num += to_end;

        *pnum += to_end;



        if (offset > 0) {

            prev_end_off += to_end;

        }

    }

    return start_off;

}



static int64_t allocate_cluster(BlockDriverState *bs, int64_t sector_num)

{

    BDRVParallelsState *s = bs->opaque;
@@ -148,11 +177,9 @@ static int64_t coroutine_fn parallels_co_get_block_status(BlockDriverState *bs, 
    int64_t offset;



    qemu_co_mutex_lock(&s->lock);

    offset = seek_to_sector(s, sector_num);

    offset = block_status(s, sector_num, nb_sectors, pnum);

    qemu_co_mutex_unlock(&s->lock);



    *pnum = cluster_remainder(s, sector_num, nb_sectors);



    if (offset < 0) {

        return 0;

    }
@@ -218,10 +245,9 @@ static coroutine_fn int parallels_co_readv(BlockDriverState *bs, 
        int n, nbytes;



        qemu_co_mutex_lock(&s->lock);

        position = seek_to_sector(s, sector_num);

        position = block_status(s, sector_num, nb_sectors, &n);

        qemu_co_mutex_unlock(&s->lock);



        n = cluster_remainder(s, sector_num, nb_sectors);

        nbytes = n << BDRV_SECTOR_BITS;



        if (position < 0) {