From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50746) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X482o-0004Ek-El for qemu-devel@nongnu.org; Mon, 07 Jul 2014 08:29:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1X482h-00058l-Hi for qemu-devel@nongnu.org; Mon, 07 Jul 2014 08:29:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:9253) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X482h-00058N-8v for qemu-devel@nongnu.org; Mon, 07 Jul 2014 08:29:11 -0400 From: Stefan Hajnoczi Date: Mon, 7 Jul 2014 14:28:37 +0200 Message-Id: <1404736118-10078-11-git-send-email-stefanha@redhat.com> In-Reply-To: <1404736118-10078-1-git-send-email-stefanha@redhat.com> References: <1404736118-10078-1-git-send-email-stefanha@redhat.com> Subject: [Qemu-devel] [PULL for-2.1 10/11] dataplane: submit I/O as a batch List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Peter Maydell , Ming Lei , Stefan Hajnoczi From: Ming Lei Before commit 580b6b2aa2(dataplane: use the QEMU block layer for I/O), dataplane for virtio-blk submits block I/O as a batch. This commit 580b6b2aa2 replaces the custom linux AIO implementation(including submit I/O as a batch) with QEMU block layer, but this commit causes ~40% throughput regression on virtio-blk performance, and removing submitting I/O as a batch is one of the causes. This patch applies the newly introduced bdrv_io_plug() and bdrv_io_unplug() interfaces to support submitting I/O at batch for Qemu block layer, and in my test, the change can improve throughput by ~30% with 'aio=native'. Following my fio test script: [global] direct=1 size=4G bsrange=4k-4k timeout=40 numjobs=4 ioengine=libaio iodepth=64 filename=/dev/vdc group_reporting=1 [f] rw=randread Result on one of my small machine(host: x86_64, 2cores, 4thread, guest: 4cores): - qemu master: 65K IOPS - qemu master with these patches: 92K IOPS - 2.0.0 release(dataplane using custom linux aio): 104K IOPS Reviewed-by: Paolo Bonzini Signed-off-by: Ming Lei Signed-off-by: Stefan Hajnoczi --- hw/block/dataplane/virtio-blk.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c index 4c5ba18..4bc0729 100644 --- a/hw/block/dataplane/virtio-blk.c +++ b/hw/block/dataplane/virtio-blk.c @@ -84,6 +84,7 @@ static void handle_notify(EventNotifier *e) }; event_notifier_test_and_clear(&s->host_notifier); + bdrv_io_plug(s->blk->conf.bs); for (;;) { /* Disable guest->host notifies to avoid unnecessary vmexits */ vring_disable_notification(s->vdev, &s->vring); @@ -117,6 +118,7 @@ static void handle_notify(EventNotifier *e) break; } } + bdrv_io_unplug(s->blk->conf.bs); } /* Context: QEMU global mutex held */ -- 1.9.3