diff options
| author | Peter Lieven <pl@kamp.de> | 2017-03-16 17:02:49 +0100 |
|---|---|---|
| committer | Michael Roth <mdroth@linux.vnet.ibm.com> | 2017-03-20 14:57:35 -0500 |
| commit | a3aeb9f09de2d78fa5077b6e8a66d73b7c045a0c (patch) | |
| tree | 8b4cd6434065f0c0378ff2d8f93990021125f86c | |
| parent | 34e9c09d03185256d699803d5cb6bfb22872b510 (diff) | |
thread-pool: add missing qemu_bh_cancel in completion function
commit 3c80ca15 fixed a deadlock scenarion with nested aio_poll invocations.
However, the rescheduling of the completion BH introcuded unnecessary spinning
in the main-loop. On very fast file backends this can even lead to the
"WARNING: I/O thread spun for 1000 iterations" message popping up.
Callgrind reports about 3-4% less instructions with this patch running
qemu-img bench on a ramdisk based VMDK file.
Fixes: 3c80ca158c96ff902a30883a8933e755988948b1
Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit b7a745dc33a18377bb4a8dfe54d1df01ea60bf66)
* drop context dep on b9e413d
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
| -rw-r--r-- | thread-pool.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/thread-pool.c b/thread-pool.c index 6fba913529..4157210d16 100644 --- a/thread-pool.c +++ b/thread-pool.c @@ -185,6 +185,13 @@ restart: qemu_bh_schedule(pool->completion_bh); elem->common.cb(elem->common.opaque, elem->ret); + + /* We can safely cancel the completion_bh here regardless of someone + * else having scheduled it meanwhile because we reenter the + * completion function anyway (goto restart). + */ + qemu_bh_cancel(pool->completion_bh); + qemu_aio_unref(elem); goto restart; } else { |