Try to perform IO for the biggest continuous block possible.
The performance for sequential read is increased from 220 Gb/sec to
360 Gb/sec for continous image on my SSD HDD.
Signed-off-by: Denis V. Lunev <d...@openvz.org>
CC: Roman Kagan <rka...@parallels.com>
CC: Kevin Wolf <kw...@redhat.com>
CC: Stefan Hajnoczi <stefa...@redhat.com>
---
block/parallels.c | 37 ++++++++++++++++++++++++++++++++-----
1 file changed, 32 insertions(+), 5 deletions(-)
diff --git a/block/parallels.c b/block/parallels.c
index e8b3d09..d0128c9 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -96,6 +96,35 @@ 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;
@@ -133,11 +162,9 @@ 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;
}
@@ -201,8 +228,8 @@ static coroutine_fn int parallels_co_readv(BlockDriverState
*bs,
qemu_co_mutex_lock(&s->lock);
while (nb_sectors > 0) {
- int64_t position = seek_to_sector(s, sector_num);
- int n = cluster_remainder(s, sector_num, nb_sectors);
+ int n;
+ int64_t position = block_status(s, sector_num, nb_sectors, &n);
int nbytes = n << BDRV_SECTOR_BITS;
if (position < 0) {
--
1.9.1
