| Message ID | 20210526082423.47837-3-mst@redhat.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | virtio net: spurious interrupt related fixes | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Guessed tree name to be net-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | success | CCed 6 of 6 maintainers |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 33 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
在 2021/5/26 下午4:24, Michael S. Tsirkin 写道: > 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> Acked-by: Jason Wang <jasowang@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; > } >
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; }
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(-)