This patch works to improve the performance of the query requests.
>From the commit 13344f3a, it adds a lock to make query-blockstats
safe by the aio_context_acquire(). the qmp_query_blockstats func
requires/releases the AioContext lock, which takes some time and
blocks the I/O processing. It affects the performance, especially
in the multi-disks guests.
As the low-level details of block statistics inside QEMU, we can
acquire a reference instead of the lock.
Signed-off-by: Dou Liyang <douly.f...@cn.fujitsu.com>
---
block/qapi.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/block/qapi.c b/block/qapi.c
index bc622cd..2262918 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -457,17 +457,21 @@ static BlockStats *bdrv_query_bds_stats(const
BlockDriverState *bs,
}
static BlockStats *bdrv_query_stats(BlockBackend *blk,
- const BlockDriverState *bs,
+ BlockDriverState *bs,
bool query_backing)
{
BlockStats *s;
+ bdrv_ref(bs);
s = bdrv_query_bds_stats(bs, query_backing);
+ bdrv_unref(bs);
if (blk) {
+ blk_ref(blk);
s->has_device = true;
s->device = g_strdup(blk_name(blk));
bdrv_query_blk_stats(s->stats, blk);
+ blk_unref(blk);
}
return s;
@@ -523,13 +527,8 @@ BlockStatsList *qmp_query_blockstats(bool has_query_nodes,
while (next_query_bds(&blk, &bs, query_nodes)) {
BlockStatsList *info = g_malloc0(sizeof(*info));
- AioContext *ctx = blk ? blk_get_aio_context(blk)
- : bdrv_get_aio_context(bs);
- aio_context_acquire(ctx);
info->value = bdrv_query_stats(blk, bs, !query_nodes);
- aio_context_release(ctx);
-
*p_next = info;
p_next = &info->next;
}
--
2.5.5
