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vhost_net: use vhost_add_used_and_signal_n() in vhost_zerocopy_signal_used()

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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 switch to use
vhost_add_used_and_signal_n() to avoid multiple calls to
vhost_add_used_and_signal(). Which means much less times of used index
updating and memory barriers.

2% performance improvement were seen on netperf TCP_RR test.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Wang 2013-09-02 16:40:57 +08:00 • committed by David S. Miller
parent 094afe7d55
commit c92112aed3
1 changed files with 8 additions and 5 deletions
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13
drivers/vhost/net.c
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@ -281,7 +281,7 @@ static void vhost_zerocopy_signal_used(struct vhost_net *net,
{ {
struct vhost_net_virtqueue *nvq = struct vhost_net_virtqueue *nvq =
container_of(vq, struct vhost_net_virtqueue, vq); container_of(vq, struct vhost_net_virtqueue, vq);
int i; int i, add;
int j = 0; int j = 0;
for (i = nvq->done_idx; i != nvq->upend_idx; i = (i + 1) % UIO_MAXIOV) { 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); vhost_net_tx_err(net);
if (VHOST_DMA_IS_DONE(vq->heads[i].len)) { if (VHOST_DMA_IS_DONE(vq->heads[i].len)) {
vq->heads[i].len = VHOST_DMA_CLEAR_LEN; vq->heads[i].len = VHOST_DMA_CLEAR_LEN;
vhost_add_used_and_signal(vq->dev, vq,
vq->heads[i].id, 0);
++j; ++j;
} else } else
break; break;
} }
if (j) while (j) {
nvq->done_idx = i; 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) static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)