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vhost-net: reduce vq polling on tx zerocopy

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It seems that to avoid deadlocks it is enough to poll vq before
 we are going to use the last buffer.  This is faster than
c70aa540c7.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michael S. Tsirkin 2012-11-01 09:16:55 +00:00 committed by David S. Miller
parent eaae8132ef
commit 24eb21a148
1 changed files with 11 additions and 1 deletions
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12
drivers/vhost/net.c
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@ -197,8 +197,18 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
{
struct vhost_ubuf_ref *ubufs = ubuf->ctx;
struct vhost_virtqueue *vq = ubufs->vq;
int cnt = atomic_read(&ubufs->kref.refcount);
vhost_poll_queue(&vq->poll);
/*
* 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
* (the value 16 here is more or less arbitrary, it's tuned to trigger
* less than 10% of times).
*/
if (cnt <= 2 || !(cnt % 16))
vhost_poll_queue(&vq->poll);
/* set len to mark this desc buffers done DMA */
vq->heads[ubuf->desc].len = success ?
VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN;