From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49094) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eRI1l-0005gs-Fj for qemu-devel@nongnu.org; Tue, 19 Dec 2017 08:33:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eRI1k-0003EK-HV for qemu-devel@nongnu.org; Tue, 19 Dec 2017 08:33:49 -0500 From: sochin.jiang Date: Tue, 19 Dec 2017 21:33:03 +0800 Message-ID: <1513690383-27269-1-git-send-email-sochin.jiang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain Subject: [Qemu-devel] [PATCH] virtio-blk: notify guest directly List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: stefanha@redhat.com, kwolf@redhat.com, mreitz@redhat.com Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, sochin.jiang@huawei.com, eric.fangyi@huawei.com From: "sochin.jiang" Till now, we've already notify guest as a batch mostly, an extra BH won't decrease guest interrupts much, but cause a significant notification loss. Generally, we could have 15% or so performance lost in single queue IO models, as I tested. Signed-off-by: sochin.jiang --- hw/block/dataplane/virtio-blk.c | 19 +++++++------------ 1 file changed, 7 insertions(+), 12 deletions(-) diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c index 5556f0e..a261a1d 100644 --- a/hw/block/dataplane/virtio-blk.c +++ b/hw/block/dataplane/virtio-blk.c @@ -32,7 +32,6 @@ struct VirtIOBlockDataPlane { VirtIOBlkConf *conf; VirtIODevice *vdev; - QEMUBH *bh; /* bh for guest notification */ unsigned long *batch_notify_vqs; /* Note that these EventNotifiers are assigned by value. This is @@ -44,14 +43,7 @@ struct VirtIOBlockDataPlane { AioContext *ctx; }; -/* Raise an interrupt to signal guest, if necessary */ -void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s, VirtQueue *vq) -{ - set_bit(virtio_get_queue_index(vq), s->batch_notify_vqs); - qemu_bh_schedule(s->bh); -} - -static void notify_guest_bh(void *opaque) +static void notify_guest(void *opaque) { VirtIOBlockDataPlane *s = opaque; unsigned nvqs = s->conf->num_queues; @@ -75,7 +67,12 @@ static void notify_guest_bh(void *opaque) } } -/* Context: QEMU global mutex held */ +/* Raise an interrupt to signal guest, if necessary */ +void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s, VirtQueue *vq) +{ + set_bit(virtio_get_queue_index(vq), s->batch_notify_vqs); + notify_guest(s); +} void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf, VirtIOBlockDataPlane **dataplane, Error **errp) @@ -122,7 +119,6 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf, } else { s->ctx = qemu_get_aio_context(); } - s->bh = aio_bh_new(s->ctx, notify_guest_bh, s); s->batch_notify_vqs = bitmap_new(conf->num_queues); *dataplane = s; @@ -140,7 +136,6 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s) vblk = VIRTIO_BLK(s->vdev); assert(!vblk->dataplane_started); g_free(s->batch_notify_vqs); - qemu_bh_delete(s->bh); if (s->iothread) { object_unref(OBJECT(s->iothread)); } -- 1.8.3.1