Commit b7a745dc authored by Peter Lieven's avatar Peter Lieven Committed by Kevin Wolf
Browse files

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: 3c80ca15
Cc: qemu-stable@nongnu.org
Signed-off-by: default avatarPeter Lieven <pl@kamp.de>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 8cd1a3e4

util/thread-pool.c

+7 −0
Original line number Diff line number Diff line
@@ -188,6 +188,13 @@ restart: 
            aio_context_release(pool->ctx);

            elem->common.cb(elem->common.opaque, elem->ret);

            aio_context_acquire(pool->ctx);



            /* 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 {