[Qemu-devel] [PATCH RFC 05/14] dataplane: enable selective bypassing coroutine

[Ming Lei <ming.lei@canonical.com>]

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

With this patch, ~16% thoughput improvement can
be observed in my laptop based VM test, and ~7%
improvement is observed in the VM based on server.

Signed-off-by: Ming Lei <ming.lei@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 d6ba65c..2093e4a 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -28,6 +28,7 @@ struct VirtIOBlockDataPlane {
     bool started;
     bool starting;
     bool stopping;
+    bool raw_format;
 
     VirtIOBlkConf *blk;
 
@@ -193,6 +194,8 @@ 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;
 }
 
@@ -262,6 +265,10 @@ 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) {
+        qemu_aio_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);
@@ -291,6 +298,9 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
 
     aio_context_release(s->ctx);
 
+    if (s->raw_format) {
+        qemu_aio_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