vhost_net: use vhost_add_used_and_signal_n() in vhost_zerocopy_signal_used() (c92112ae) · Commits · 戴 / test

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>

drivers/vhost/net.c

+8 −5

Original line number	Diff line number	Diff line
		@@ -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)

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