Re: [PATCH 2/6] vhost_net: use vhost_add_used_and_signal_n() in vhost_zerocopy_signal_used()
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2013-08-16 09:52:46
Also in:
kvm, lkml, netdev
On Fri, Aug 16, 2013 at 01:16:26PM +0800, Jason Wang wrote:
Switch to use vhost_add_used_and_signal_n() to avoid multiple calls to vhost_add_used_and_signal(). With the patch we will call at most 2 times (consider done_idx warp around) compared to N times w/o this patch. Signed-off-by: Jason Wang <redacted>
So? Does this help performance then?
quoted hunk ↗ jump to hunk
--- 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