Messages in this thread Patch in this message | | | Date | Wed, 26 May 2021 04:24:37 -0400 | From | "Michael S. Tsirkin" <> | Subject | [PATCH v3 2/4] 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> --- drivers/net/virtio_net.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 12512d1002ec..c29f42d1e04f 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1434,11 +1434,12 @@ 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) @@ -1522,6 +1523,9 @@ 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); @@ -1542,9 +1546,6 @@ 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; } -- MST
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