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authorRusty Russell <rusty@rustcorp.com.au>2012-01-12 15:44:42 +1030
committerRusty Russell <rusty@rustcorp.com.au>2012-01-12 15:44:42 +1030
commit7b21e34fd1c272e3a8c3846168f2f6287a4cd72b (patch)
tree0f94c9f834f5b7cd8ba87168df892ed17b09cb8f /drivers/lguest/lguest_device.c
parente343a895a9f342f239c5e3c5ffc6c0b1707e6244 (diff)
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>
Diffstat (limited to 'drivers/lguest/lguest_device.c')
-rw-r--r--drivers/lguest/lguest_device.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c
index 595d7319701..6a1d6447b86 100644
--- a/drivers/lguest/lguest_device.c
+++ b/drivers/lguest/lguest_device.c
@@ -292,10 +292,12 @@ static struct virtqueue *lg_find_vq(struct virtio_device *vdev,
/*
* OK, tell virtio_ring.c to set up a virtqueue now we know its size
- * and we've got a pointer to its pages.
+ * and we've got a pointer to its pages. Note that we set weak_barriers
+ * to 'true': the host just a(nother) SMP CPU, so we only need inter-cpu
+ * barriers.
*/
- vq = vring_new_virtqueue(lvq->config.num, LGUEST_VRING_ALIGN,
- vdev, lvq->pages, lg_notify, callback, name);
+ vq = vring_new_virtqueue(lvq->config.num, LGUEST_VRING_ALIGN, vdev,
+ true, lvq->pages, lg_notify, callback, name);
if (!vq) {
err = -ENOMEM;
goto unmap;