Commit 19f5dc15 authored by Denis V. Lunev's avatar Denis V. Lunev Committed by Stefan Hajnoczi
Browse files

block/parallels: optimize linear image expansion 



Plain image expansion spends a lot of time to update image file size.
This seriously affects the performance. The following simple test
  qemu_img create -f parallels -o cluster_size=64k ./1.hds 64G
  qemu_io -n -c "write -P 0x11 0 1024M" ./1.hds
could be improved if the format driver will pre-allocate some space
in the image file with a reasonable chunk.

This patch preallocates 128 Mb using bdrv_write_zeroes, which should
normally use fallocate() call inside. Fallback to older truncate()
could be used as a fallback using image open options thanks to the
previous patch.

The benefit is around 15%.

Signed-off-by: default avatarDenis V. Lunev <den@openvz.org>
Reviewed-by: default avatarRoman Karan <rkagan@parallels.com>
Signed-off-by: default avatarRoman Kagan <rkagan@parallels.com>
Message-id: 1430207220-24458-27-git-send-email-den@openvz.org
CC: Kevin Wolf <kwolf@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent d6179011

block/parallels.c

+32 −10
Original line number Diff line number Diff line
@@ -88,6 +88,7 @@ typedef struct BDRVParallelsState { 
    uint32_t *bat_bitmap;

    unsigned int bat_size;



    int64_t  data_end;

    uint64_t prealloc_size;

    ParallelsPreallocMode prealloc_mode;
@@ -187,7 +188,6 @@ static int64_t allocate_cluster(BlockDriverState *bs, int64_t sector_num) 
    BDRVParallelsState *s = bs->opaque;

    uint32_t idx, offset;

    int64_t pos;

    int ret;



    idx = sector_num / s->tracks;

    offset = sector_num % s->tracks;
@@ -200,14 +200,21 @@ static int64_t allocate_cluster(BlockDriverState *bs, int64_t sector_num) 
    }



    pos = bdrv_getlength(bs->file) >> BDRV_SECTOR_BITS;

    if (s->prealloc_mode == PRL_PREALLOC_MODE_TRUNCATE) {

        ret = bdrv_truncate(bs->file, (pos + s->tracks) << BDRV_SECTOR_BITS);

    if (s->data_end + s->tracks > pos) {

        int ret;

        if (s->prealloc_mode == PRL_PREALLOC_MODE_FALLOCATE) {

            ret = bdrv_write_zeroes(bs->file, s->data_end,

                                    s->prealloc_size, 0);

        } else {

        ret = bdrv_write_zeroes(bs->file, pos, s->tracks, 0);

            ret = bdrv_truncate(bs->file,

                    (s->data_end + s->prealloc_size) << BDRV_SECTOR_BITS);

        }

        if (ret < 0) {

            return ret;

        }

    }

    pos = s->data_end;

    s->data_end += s->tracks;



    s->bat_bitmap[idx] = cpu_to_le32(pos / s->off_multiplier);
@@ -549,7 +556,7 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags, 
{

    BDRVParallelsState *s = bs->opaque;

    ParallelsHeader ph;

    int ret, size;

    int ret, size, i;

    QemuOpts *opts = NULL;

    Error *local_err = NULL;

    char *buf;
@@ -599,7 +606,11 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags, 
        ret = -ENOMEM;

        goto fail;

    }

    if (le32_to_cpu(ph.data_off) < s->header_size) {

    s->data_end = le32_to_cpu(ph.data_off);

    if (s->data_end == 0) {

        s->data_end = ROUND_UP(bat_entry_off(s->bat_size), BDRV_SECTOR_SIZE);

    }

    if (s->data_end < s->header_size) {

        /* there is not enough unused space to fit to block align between BAT

           and actual data. We can't avoid read-modify-write... */

        s->header_size = size;
@@ -611,6 +622,13 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags, 
    }

    s->bat_bitmap = (uint32_t *)(s->header + 1);



    for (i = 0; i < s->bat_size; i++) {

        int64_t off = bat2sect(s, i);

        if (off >= s->data_end) {

            s->data_end = off + s->tracks;

        }

    }



    if (le32_to_cpu(ph.inuse) == HEADER_INUSE_MAGIC) {

        /* Image was not closed correctly. The check is mandatory */

        s->header_unclean = true;
@@ -685,6 +703,10 @@ static void parallels_close(BlockDriverState *bs) 
        parallels_update_header(bs);

    }



    if (bs->open_flags & BDRV_O_RDWR) {

        bdrv_truncate(bs->file, s->data_end << BDRV_SECTOR_BITS);

    }



    g_free(s->bat_dirty_bmap);

    qemu_vfree(s->header);

}