[Qemu-devel] [PATCH v1 09/17] dataplane: enable selective bypassing coroutine

[Ming Lei]

This patch enables selective bypassing for the
coroutine in bdrv_co_aio_rw_vector() if the image
format is raw.

With this patch, ~10% throughput improvement for raw image is
observed in the VM based on server.

Signed-off-by: Ming Lei <ming....@canonical.com>
---
 hw/block/dataplane/virtio-blk.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index c9a8cc2..a0732e3 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -30,6 +30,7 @@ struct VirtIOBlockDataPlane {
     bool started;
     bool starting;
     bool stopping;
+    bool raw_format;
 
     VirtIOBlkConf *blk;
 
@@ -199,6 +200,8 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, 
VirtIOBlkConf *blk,
     error_setg(&s->blocker, "block device is in use by data plane");
     bdrv_op_block_all(blk->conf.bs, s->blocker);
 
+    s->raw_format = (raw_get_aio_fd(blk->conf.bs) >= 0);
+
     *dataplane = s;
 }
 
@@ -272,6 +275,10 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
     /* Kick right away to begin processing requests already in vring */
     event_notifier_set(virtio_queue_get_host_notifier(vq));
 
+    if (s->raw_format) {
+        bdrv_set_bypass_co(s->ctx, true);
+    }
+
     /* Get this show started by hooking up our callbacks */
     aio_context_acquire(s->ctx);
     aio_set_event_notifier(s->ctx, &s->host_notifier, handle_notify);
@@ -303,6 +310,9 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
 
     vblk->obj_pool = NULL;
 
+    if (s->raw_format) {
+        bdrv_set_bypass_co(s->ctx, false);
+    }
     /* Sync vring state back to virtqueue so that non-dataplane request
      * processing can continue when we disable the host notifier below.
      */
-- 
1.7.9.5