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virtio_net: move txq wakeups under tx q lock

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We currently check num_free outside tx q lock
which is unsafe: new packets can arrive meanwhile
and there won't be space in the queue.
Thus a spurious queue wakeup causing overhead
and even packet drops.

Move the check under the lock to fix that.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2021-04-13 01:38:08 -04:00
parent 5a2f966d0f
commit 22bc63c58e
1 changed files with 7 additions and 6 deletions
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13
drivers/net/virtio_net.c
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@ -1517,11 +1517,12 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
if (__netif_tx_trylock(txq)) {
free_old_xmit_skbs(sq, true);
if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
netif_tx_wake_queue(txq);
__netif_tx_unlock(txq);
}
if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
netif_tx_wake_queue(txq);
}
static int virtnet_poll(struct napi_struct *napi, int budget)
@ -1606,6 +1607,9 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
virtqueue_disable_cb(sq->vq);
free_old_xmit_skbs(sq, true);
if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
netif_tx_wake_queue(txq);
opaque = virtqueue_enable_cb_prepare(sq->vq);
done = napi_complete_done(napi, 0);
@ -1626,9 +1630,6 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
}
}
if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
netif_tx_wake_queue(txq);
return 0;
}