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block/parallels: improve image reading performance

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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: Denis V. Lunev <den@openvz.org>
Reviewed-by: Roman Kagan <rkagan@parallels.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Roman Kagan <rkagan@parallels.com>
Message-id: 1430207220-24458-23-git-send-email-den@openvz.org
CC: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Denis V. Lunev 2015-04-28 10:46:55 +03:00 committed by Stefan Hajnoczi
parent a6be831e99
commit 6953d92078
1 changed files with 31 additions and 5 deletions
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36
block/parallels.c
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@ -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) {