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[Qemu-devel] [PATCH] block: Let bdrv_drain_all() to call aio_poll() for
From: |
Alexander Yarygin |
Subject: |
[Qemu-devel] [PATCH] block: Let bdrv_drain_all() to call aio_poll() for each AioContext |
Date: |
Wed, 13 May 2015 18:18:31 +0300 |
After the commit 9b536adc ("block: acquire AioContext in
bdrv_drain_all()") the aio_poll() function got called for every
BlockDriverState, in assumption that every device may have its own
AioContext. The bdrv_drain_all() function is called in each
virtio_reset() call, which in turn is called for every virtio-blk
device on initialization, so we got aio_poll() called
'length(device_list)^2' times.
If we have thousands of disks attached, there are a lot of
BlockDriverStates but only a few AioContexts, leading to tons of
unnecessary aio_poll() calls. For example, startup times with 1000 disks
takes over 13 minutes.
This patch changes the bdrv_drain_all() function allowing it find shared
AioContexts and to call aio_poll() only for unique ones. This results in
much better startup times, e.g. 1000 disks do come up within 5 seconds.
Cc: Christian Borntraeger <address@hidden>
Cc: Cornelia Huck <address@hidden>
Cc: Kevin Wolf <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Cc: Stefan Hajnoczi <address@hidden>
Signed-off-by: Alexander Yarygin <address@hidden>
---
block.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/block.c b/block.c
index f2f8ae7..7414815 100644
--- a/block.c
+++ b/block.c
@@ -1994,7 +1994,6 @@ static bool bdrv_drain_one(BlockDriverState *bs)
bdrv_flush_io_queue(bs);
bdrv_start_throttled_reqs(bs);
bs_busy = bdrv_requests_pending(bs);
- bs_busy |= aio_poll(bdrv_get_aio_context(bs), bs_busy);
return bs_busy;
}
@@ -2010,8 +2009,12 @@ static bool bdrv_drain_one(BlockDriverState *bs)
*/
void bdrv_drain(BlockDriverState *bs)
{
- while (bdrv_drain_one(bs)) {
+ bool busy = true;
+
+ while (busy) {
/* Keep iterating */
+ busy = bdrv_drain_one(bs);
+ busy |= aio_poll(bdrv_get_aio_context(bs), busy);
}
}
@@ -2032,6 +2035,7 @@ void bdrv_drain_all(void)
/* Always run first iteration so any pending completion BHs run */
bool busy = true;
BlockDriverState *bs;
+ GList *aio_ctxs = NULL;
while (busy) {
busy = false;
@@ -2041,9 +2045,14 @@ void bdrv_drain_all(void)
aio_context_acquire(aio_context);
busy |= bdrv_drain_one(bs);
+ if (!aio_ctxs || !g_list_find(aio_ctxs, aio_context)) {
+ busy |= aio_poll(aio_context, busy);
+ aio_ctxs = g_list_append(aio_ctxs, aio_context);
+ }
aio_context_release(aio_context);
}
}
+ g_list_free(aio_ctxs);
}
/* make a BlockDriverState anonymous by removing from bdrv_state and
--
1.9.1
- [Qemu-devel] [PATCH] block: Let bdrv_drain_all() to call aio_poll() for each AioContext,
Alexander Yarygin <=
Re: [Qemu-devel] [Qemu-block] [PATCH] block: Let bdrv_drain_all() to call aio_poll() for each AioContext, Alberto Garcia, 2015/05/13