| Message ID | 1377836962-49780-3-git-send-email-jasowang@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Aug 30, 2013 at 12:29:18PM +0800, Jason Wang wrote: > We tend to batch the used adding and signaling in vhost_zerocopy_callback() > which may result more than 100 used buffers to be updated in > vhost_zerocopy_signal_used() in some cases. So wwitch to use switch > vhost_add_used_and_signal_n() to avoid multiple calls to > vhost_add_used_and_signal(). Which means much more less times of used index > updating and memory barriers. pls put info on perf gain in commit log too > > Signed-off-by: Jason Wang <jasowang@redhat.com> > --- > drivers/vhost/net.c | 13 ++++++++----- > 1 files changed, 8 insertions(+), 5 deletions(-) > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > index 280ee66..8a6dd0d 100644 > --- a/drivers/vhost/net.c > +++ b/drivers/vhost/net.c > @@ -281,7 +281,7 @@ static void vhost_zerocopy_signal_used(struct vhost_net *net, > { > struct vhost_net_virtqueue *nvq = > container_of(vq, struct vhost_net_virtqueue, vq); > - int i; > + int i, add; > int j = 0; > > for (i = nvq->done_idx; i != nvq->upend_idx; i = (i + 1) % UIO_MAXIOV) { > @@ -289,14 +289,17 @@ static void vhost_zerocopy_signal_used(struct vhost_net *net, > vhost_net_tx_err(net); > if (VHOST_DMA_IS_DONE(vq->heads[i].len)) { > vq->heads[i].len = VHOST_DMA_CLEAR_LEN; > - vhost_add_used_and_signal(vq->dev, vq, > - vq->heads[i].id, 0); > ++j; > } else > break; > } > - if (j) > - nvq->done_idx = i; > + while (j) { > + add = min(UIO_MAXIOV - nvq->done_idx, j); > + vhost_add_used_and_signal_n(vq->dev, vq, > + &vq->heads[nvq->done_idx], add); > + nvq->done_idx = (nvq->done_idx + add) % UIO_MAXIOV; > + j -= add; > + } > } > > static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success) > -- > 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 09/02/2013 01:50 PM, Michael S. Tsirkin wrote: > On Fri, Aug 30, 2013 at 12:29:18PM +0800, Jason Wang wrote: >> > We tend to batch the used adding and signaling in vhost_zerocopy_callback() >> > which may result more than 100 used buffers to be updated in >> > vhost_zerocopy_signal_used() in some cases. So wwitch to use > switch Ok. >> > vhost_add_used_and_signal_n() to avoid multiple calls to >> > vhost_add_used_and_signal(). Which means much more less times of used index >> > updating and memory barriers. > pls put info on perf gain in commit log too > Sure. -- To unsubscribe from this list: send the line "unsubscribe kvm" 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 280ee66..8a6dd0d 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -281,7 +281,7 @@ static void vhost_zerocopy_signal_used(struct vhost_net *net, { struct vhost_net_virtqueue *nvq = container_of(vq, struct vhost_net_virtqueue, vq); - int i; + int i, add; int j = 0; for (i = nvq->done_idx; i != nvq->upend_idx; i = (i + 1) % UIO_MAXIOV) { @@ -289,14 +289,17 @@ static void vhost_zerocopy_signal_used(struct vhost_net *net, vhost_net_tx_err(net); if (VHOST_DMA_IS_DONE(vq->heads[i].len)) { vq->heads[i].len = VHOST_DMA_CLEAR_LEN; - vhost_add_used_and_signal(vq->dev, vq, - vq->heads[i].id, 0); ++j; } else break; } - if (j) - nvq->done_idx = i; + while (j) { + add = min(UIO_MAXIOV - nvq->done_idx, j); + vhost_add_used_and_signal_n(vq->dev, vq, + &vq->heads[nvq->done_idx], add); + nvq->done_idx = (nvq->done_idx + add) % UIO_MAXIOV; + j -= add; + } } static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
We tend to batch the used adding and signaling in vhost_zerocopy_callback() which may result more than 100 used buffers to be updated in vhost_zerocopy_signal_used() in some cases. So wwitch to use vhost_add_used_and_signal_n() to avoid multiple calls to vhost_add_used_and_signal(). Which means much more less times of used index updating and memory barriers. Signed-off-by: Jason Wang <jasowang@redhat.com> --- drivers/vhost/net.c | 13 ++++++++----- 1 files changed, 8 insertions(+), 5 deletions(-)