Message ID | 3e57e2cde71a4270a8fef395c31f5f0e8a130c28.1351524502.git.mst@redhat.com |
---|---|
State | Superseded, archived |
Delegated to: | David Miller |
Headers | show |
On 10/29/2012 11:49 AM, Michael S. Tsirkin wrote: > It seems that to avoid deadlocks it is enough to poll vq before > we are going to use the last buffer. This should be faster than > c70aa540c7a9f67add11ad3161096fb95233aa2e. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > drivers/vhost/net.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > index 8e9de79..3967f82 100644 > --- a/drivers/vhost/net.c > +++ b/drivers/vhost/net.c > @@ -197,8 +197,16 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, int status) > { > struct vhost_ubuf_ref *ubufs = ubuf->ctx; > struct vhost_virtqueue *vq = ubufs->vq; > - > - vhost_poll_queue(&vq->poll); > + int cnt = atomic_read(&ubufs->kref.refcount); > + > + /* > + * Trigger polling thread if guest stopped submitting new buffers: > + * in this case, the refcount after decrement will eventually reach 1 > + * so here it is 2. > + * We also trigger polling periodically after each 16 packets. > + */ > + if (cnt <= 2 || !(cnt % 16)) Why 16? Does it make sense to make it configurable? -vlad > + vhost_poll_queue(&vq->poll); > /* set len to mark this desc buffers done DMA */ > vq->heads[ubuf->desc].len = status ? > VHOST_DMA_FAILED_LEN : VHOST_DMA_DONE_LEN; > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Oct 30, 2012 at 11:47:45AM -0400, Vlad Yasevich wrote: > On 10/29/2012 11:49 AM, Michael S. Tsirkin wrote: > >It seems that to avoid deadlocks it is enough to poll vq before > > we are going to use the last buffer. This should be faster than > >c70aa540c7a9f67add11ad3161096fb95233aa2e. > > > >Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > >--- > > drivers/vhost/net.c | 12 ++++++++++-- > > 1 file changed, 10 insertions(+), 2 deletions(-) > > > >diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > >index 8e9de79..3967f82 100644 > >--- a/drivers/vhost/net.c > >+++ b/drivers/vhost/net.c > >@@ -197,8 +197,16 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, int status) > > { > > struct vhost_ubuf_ref *ubufs = ubuf->ctx; > > struct vhost_virtqueue *vq = ubufs->vq; > >- > >- vhost_poll_queue(&vq->poll); > >+ int cnt = atomic_read(&ubufs->kref.refcount); > >+ > >+ /* > >+ * Trigger polling thread if guest stopped submitting new buffers: > >+ * in this case, the refcount after decrement will eventually reach 1 > >+ * so here it is 2. > >+ * We also trigger polling periodically after each 16 packets. > >+ */ > >+ if (cnt <= 2 || !(cnt % 16)) > > Why 16? Does it make sense to make it configurable? > > -vlad Probably not but I'll add a comment explaining why. > >+ vhost_poll_queue(&vq->poll); > > /* set len to mark this desc buffers done DMA */ > > vq->heads[ubuf->desc].len = status ? > > VHOST_DMA_FAILED_LEN : VHOST_DMA_DONE_LEN; > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 8e9de79..3967f82 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -197,8 +197,16 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, int status) { struct vhost_ubuf_ref *ubufs = ubuf->ctx; struct vhost_virtqueue *vq = ubufs->vq; - - vhost_poll_queue(&vq->poll); + int cnt = atomic_read(&ubufs->kref.refcount); + + /* + * Trigger polling thread if guest stopped submitting new buffers: + * in this case, the refcount after decrement will eventually reach 1 + * so here it is 2. + * We also trigger polling periodically after each 16 packets. + */ + if (cnt <= 2 || !(cnt % 16)) + vhost_poll_queue(&vq->poll); /* set len to mark this desc buffers done DMA */ vq->heads[ubuf->desc].len = status ? VHOST_DMA_FAILED_LEN : VHOST_DMA_DONE_LEN;
It seems that to avoid deadlocks it is enough to poll vq before we are going to use the last buffer. This should be faster than c70aa540c7a9f67add11ad3161096fb95233aa2e. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- drivers/vhost/net.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)