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[Qemu-devel] [PATCH 1/9] virtio-blk: use batch notify in non-dataplane c
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH 1/9] virtio-blk: use batch notify in non-dataplane case |
Date: |
Fri, 20 May 2016 16:40:24 -0700 |
Commit 5b2ffbe4d99843fd8305c573a100047a8c962327 ("virtio-blk: dataplane:
notify guest as a batch") deferred guest notification to a BH in order
batch notifications. This optimization is not specific to dataplane so
move it to the generic virtio-blk code that is shared by both dataplane
and non-dataplane code.
Note that this patch adds a flush function to force pending
notifications. This way we can ensure notifications do not cross device
reset or vmstate saving.
Cc: Ming Lei <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
hw/block/dataplane/virtio-blk.c | 10 ----------
hw/block/virtio-blk.c | 37 +++++++++++++++++++++++++++++++------
include/hw/virtio/virtio-blk.h | 1 +
3 files changed, 32 insertions(+), 16 deletions(-)
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 3cb97c9..e0ac4f4 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -35,7 +35,6 @@ struct VirtIOBlockDataPlane {
VirtIODevice *vdev;
VirtQueue *vq; /* virtqueue vring */
EventNotifier *guest_notifier; /* irq */
- QEMUBH *bh; /* bh for guest notification */
Notifier insert_notifier, remove_notifier;
@@ -54,13 +53,6 @@ struct VirtIOBlockDataPlane {
/* Raise an interrupt to signal guest, if necessary */
void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s)
{
- qemu_bh_schedule(s->bh);
-}
-
-static void notify_guest_bh(void *opaque)
-{
- VirtIOBlockDataPlane *s = opaque;
-
if (!virtio_should_notify(s->vdev, s->vq)) {
return;
}
@@ -156,7 +148,6 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev,
VirtIOBlkConf *conf,
object_ref(OBJECT(s->iothread));
}
s->ctx = iothread_get_aio_context(s->iothread);
- s->bh = aio_bh_new(s->ctx, notify_guest_bh, s);
s->insert_notifier.notify = data_plane_blk_insert_notifier;
s->remove_notifier.notify = data_plane_blk_remove_notifier;
@@ -179,7 +170,6 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
data_plane_remove_op_blockers(s);
notifier_remove(&s->insert_notifier);
notifier_remove(&s->remove_notifier);
- qemu_bh_delete(s->bh);
object_unref(OBJECT(s->iothread));
g_free(s);
}
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 284e646..0eaf6bf 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -45,20 +45,37 @@ void virtio_blk_free_request(VirtIOBlockReq *req)
}
}
+/* Many requests can complete in an event loop iteration, we only notify the
+ * guest once.
+ */
+static void virtio_blk_batch_notify_bh(void *opaque)
+{
+ VirtIOBlock *s = opaque;
+ VirtIODevice *vdev = VIRTIO_DEVICE(s);
+
+ if (s->dataplane_started && !s->dataplane_disabled) {
+ virtio_blk_data_plane_notify(s->dataplane);
+ } else {
+ virtio_notify(vdev, s->vq);
+ }
+}
+
+/* Force batch notifications to run */
+static void virtio_blk_batch_notify_flush(VirtIOBlock *s)
+{
+ qemu_bh_cancel(s->batch_notify_bh);
+ virtio_blk_batch_notify_bh(s);
+}
+
static void virtio_blk_req_complete(VirtIOBlockReq *req, unsigned char status)
{
VirtIOBlock *s = req->dev;
- VirtIODevice *vdev = VIRTIO_DEVICE(s);
trace_virtio_blk_req_complete(req, status);
stb_p(&req->in->status, status);
virtqueue_push(s->vq, &req->elem, req->in_len);
- if (s->dataplane_started && !s->dataplane_disabled) {
- virtio_blk_data_plane_notify(s->dataplane);
- } else {
- virtio_notify(vdev, s->vq);
- }
+ qemu_bh_schedule(s->batch_notify_bh);
}
static int virtio_blk_handle_rw_error(VirtIOBlockReq *req, int error,
@@ -664,6 +681,8 @@ static void virtio_blk_reset(VirtIODevice *vdev)
if (s->dataplane) {
virtio_blk_data_plane_stop(s->dataplane);
}
+
+ virtio_blk_batch_notify_flush(s);
aio_context_release(ctx);
blk_set_enable_write_cache(s->blk, s->original_wce);
@@ -801,6 +820,8 @@ static void virtio_blk_save(QEMUFile *f, void *opaque)
virtio_blk_data_plane_stop(s->dataplane);
}
+ virtio_blk_batch_notify_flush(s);
+
virtio_save(vdev, f);
}
@@ -896,6 +917,9 @@ static void virtio_blk_device_realize(DeviceState *dev,
Error **errp)
return;
}
+ s->batch_notify_bh = aio_bh_new(blk_get_aio_context(s->blk),
+ virtio_blk_batch_notify_bh, s);
+
s->change = qemu_add_vm_change_state_handler(virtio_blk_dma_restart_cb, s);
register_savevm(dev, "virtio-blk", virtio_blk_id++, 2,
virtio_blk_save, virtio_blk_load, s);
@@ -910,6 +934,7 @@ static void virtio_blk_device_unrealize(DeviceState *dev,
Error **errp)
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
VirtIOBlock *s = VIRTIO_BLK(dev);
+ qemu_bh_delete(s->batch_notify_bh);
virtio_blk_data_plane_destroy(s->dataplane);
s->dataplane = NULL;
qemu_del_vm_change_state_handler(s->change);
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index 8f2b056..b3834bc 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -49,6 +49,7 @@ typedef struct VirtIOBlock {
VirtQueue *vq;
void *rq;
QEMUBH *bh;
+ QEMUBH *batch_notify_bh;
VirtIOBlkConf conf;
unsigned short sector_mask;
bool original_wce;
--
2.5.5