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mirror: Speed up bitmap initial scanning

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Limiting to sectors_per_chunk for each bdrv_is_allocated_above is slow,
because the underlying protocol driver would issue much more queries
than necessary. We should coalesce the query.

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: <1436413678-7114-4-git-send-email-famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Fam Zheng 2015-07-09 11:47:58 +08:00 committed by Stefan Hajnoczi
parent 774ee4772b
commit 9990069758
1 changed files with 6 additions and 8 deletions
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14
block/mirror.c
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@ -388,7 +388,7 @@ static void coroutine_fn mirror_run(void *opaque)
MirrorBlockJob *s = opaque;
MirrorExitData *data;
BlockDriverState *bs = s->common.bs;
int64_t sector_num, end, sectors_per_chunk, length;
int64_t sector_num, end, length;
uint64_t last_pause_ns;
BlockDriverInfo bdi;
char backing_filename[2]; /* we only need 2 characters because we are only
@ -442,7 +442,6 @@ static void coroutine_fn mirror_run(void *opaque)
goto immediate_exit;
}
sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
mirror_free_init(s);
last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
@ -450,7 +449,9 @@ static void coroutine_fn mirror_run(void *opaque)
/* First part, loop on the sectors and initialize the dirty bitmap. */
BlockDriverState *base = s->base;
for (sector_num = 0; sector_num < end; ) {
int64_t next = (sector_num | (sectors_per_chunk - 1)) + 1;
/* Just to make sure we are not exceeding int limit. */
int nb_sectors = MIN(INT_MAX >> BDRV_SECTOR_BITS,
end - sector_num);
int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
if (now - last_pause_ns > SLICE_TIME) {
@ -462,8 +463,7 @@ static void coroutine_fn mirror_run(void *opaque)
goto immediate_exit;
}
ret = bdrv_is_allocated_above(bs, base,
sector_num, next - sector_num, &n);
ret = bdrv_is_allocated_above(bs, base, sector_num, nb_sectors, &n);
if (ret < 0) {
goto immediate_exit;
@ -472,10 +472,8 @@ static void coroutine_fn mirror_run(void *opaque)
assert(n > 0);
if (ret == 1) {
bdrv_set_dirty_bitmap(s->dirty_bitmap, sector_num, n);
sector_num = next;
} else {
sector_num += n;
}
sector_num += n;
}
}