* [Qemu-devel] [PATCH v1 1/2] virtio-blk: data-plane: fix save/set .complete_request in start
2014-07-05 4:18 [Qemu-devel] [PATCH v1 0/2] virtio-blk: dataplane: one fix plus one optimization Ming Lei
@ 2014-07-05 4:18 ` Ming Lei
2014-07-07 6:15 ` Fam Zheng
2014-07-05 4:18 ` [Qemu-devel] [PATCH v1 2/2] virtio-blk: dataplane: notify guest as a batch Ming Lei
1 sibling, 1 reply; 4+ messages in thread
From: Ming Lei @ 2014-07-05 4:18 UTC (permalink / raw)
To: Peter Maydell, qemu-devel, Paolo Bonzini, Stefan Hajnoczi
Cc: Kevin Wolf, Ming Lei, Fam Zheng, Michael S. Tsirkin
The callback has to be saved and reset in virtio_blk_data_plane_start(),
otherwise dataplane's requests will be completed in qemu aio context.
Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
hw/block/dataplane/virtio-blk.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 227bb15..e88862d 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -125,7 +125,6 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
Error **errp)
{
VirtIOBlockDataPlane *s;
- VirtIOBlock *vblk = VIRTIO_BLK(vdev);
Error *local_err = NULL;
BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
@@ -178,8 +177,6 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
bdrv_op_block_all(blk->conf.bs, s->blocker);
*dataplane = s;
- s->saved_complete_request = vblk->complete_request;
- vblk->complete_request = complete_request_vring;
}
/* Context: QEMU global mutex held */
@@ -201,6 +198,7 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
{
BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s->vdev)));
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+ VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
VirtQueue *vq;
if (s->started) {
@@ -234,6 +232,9 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
}
s->host_notifier = *virtio_queue_get_host_notifier(vq);
+ s->saved_complete_request = vblk->complete_request;
+ vblk->complete_request = complete_request_vring;
+
s->starting = false;
s->started = true;
trace_virtio_blk_data_plane_start(s);
--
1.7.9.5
^ permalink raw reply related [flat|nested] 4+ messages in thread* [Qemu-devel] [PATCH v1 2/2] virtio-blk: dataplane: notify guest as a batch
2014-07-05 4:18 [Qemu-devel] [PATCH v1 0/2] virtio-blk: dataplane: one fix plus one optimization Ming Lei
2014-07-05 4:18 ` [Qemu-devel] [PATCH v1 1/2] virtio-blk: data-plane: fix save/set .complete_request in start Ming Lei
@ 2014-07-05 4:18 ` Ming Lei
1 sibling, 0 replies; 4+ messages in thread
From: Ming Lei @ 2014-07-05 4:18 UTC (permalink / raw)
To: Peter Maydell, qemu-devel, Paolo Bonzini, Stefan Hajnoczi
Cc: Kevin Wolf, Ming Lei, Fam Zheng, Michael S. Tsirkin
Now requests are submitted as a batch, so it is natural
to notify guest as a batch too.
This may suppress interrupt notification to VM a lot:
- in my test, decreased by ~13K/sec
Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
hw/block/dataplane/virtio-blk.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index e88862d..d65e022 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -34,6 +34,7 @@ struct VirtIOBlockDataPlane {
VirtIODevice *vdev;
Vring vring; /* virtqueue vring */
EventNotifier *guest_notifier; /* irq */
+ QEMUBH *bh; /* bh for guest notification */
/* Note that these EventNotifiers are assigned by value. This is
* fine as long as you do not call event_notifier_cleanup on them
@@ -61,13 +62,28 @@ static void notify_guest(VirtIOBlockDataPlane *s)
event_notifier_set(s->guest_notifier);
}
+static void notify_guest_bh(void *opaque)
+{
+ VirtIOBlockDataPlane *s = opaque;
+
+ notify_guest(s);
+}
+
static void complete_request_vring(VirtIOBlockReq *req, unsigned char status)
{
+ VirtIOBlockDataPlane *s = req->dev->dataplane;
stb_p(&req->in->status, status);
- vring_push(&req->dev->dataplane->vring, &req->elem,
+ vring_push(&s->vring, &req->elem,
req->qiov.size + sizeof(*req->in));
- notify_guest(req->dev->dataplane);
+
+ /* Suppress notification to guest by BH and its scheduled
+ * flag because requests are completed as a batch after io
+ * plug & unplug is introduced, and the BH can still be
+ * executed in dataplane aio context even after it is
+ * stopped, so needn't worry about notification loss with BH.
+ */
+ qemu_bh_schedule(s->bh);
}
static void handle_notify(EventNotifier *e)
@@ -172,6 +188,7 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
s->iothread = &s->internal_iothread_obj;
}
s->ctx = iothread_get_aio_context(s->iothread);
+ s->bh = aio_bh_new(s->ctx, notify_guest_bh, s);
error_setg(&s->blocker, "block device is in use by data plane");
bdrv_op_block_all(blk->conf.bs, s->blocker);
@@ -190,6 +207,7 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
bdrv_op_unblock_all(s->blk->conf.bs, s->blocker);
error_free(s->blocker);
object_unref(OBJECT(s->iothread));
+ qemu_bh_delete(s->bh);
g_free(s);
}
--
1.7.9.5
^ permalink raw reply related [flat|nested] 4+ messages in thread