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virtio-blk: dataplane: notify guest as a batch 

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>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Ming Lei 2014-07-12 12:08:53 +08:00 committed by Stefan Hajnoczi
parent e926d9b8c5
commit 5b2ffbe4d9
1 changed files with 19 additions and 1 deletions
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20
hw/block/dataplane/virtio-blk.c
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@ -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,
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);
}