virtio: harsher barriers for rpmsg.
We were cheating with our barriers; using the smp ones rather than the
real device ones. That was fine, until rpmsg came along, which is
used to talk to a real device (a non-SMP CPU).
Unfortunately, just putting back the real barriers (reverting
d57ed95d) causes a performance regression on virtio-pci. In
particular, Amos reports netbench's TCP_RR over virtio_net CPU
utilization increased up to 35% while throughput went down by up to
14%.
By comparison, this branch is in the noise.
Reference: https://lkml.org/lkml/2011/12/11/22
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 0269717..01d6dc2 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -310,8 +310,8 @@
vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
/* Create the vring */
- vq = vring_new_virtqueue(info->num, VIRTIO_MMIO_VRING_ALIGN,
- vdev, info->queue, vm_notify, callback, name);
+ vq = vring_new_virtqueue(info->num, VIRTIO_MMIO_VRING_ALIGN, vdev,
+ true, info->queue, vm_notify, callback, name);
if (!vq) {
err = -ENOMEM;
goto error_new_virtqueue;