From: "Michael S. Tsirkin" <mst@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Jakub Kicinski <kuba@kernel.org>,
Jason Wang <jasowang@redhat.com>, Wei Wang <weiwan@google.com>,
David Miller <davem@davemloft.net>,
netdev@vger.kernel.org, Willem de Bruijn <willemb@google.com>,
virtualization@lists.linux-foundation.org
Subject: [PATCH RFC v2 4/4] virtio_net: move txq wakeups under tx q lock
Date: Tue, 13 Apr 2021 01:47:54 -0400 [thread overview]
Message-ID: <20210413054733.36363-5-mst@redhat.com> (raw)
In-Reply-To: <20210413054733.36363-1-mst@redhat.com>
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 460ccdbb840e..febaf55ec1f6 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1431,11 +1431,12 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
if (__netif_tx_trylock(txq)) {
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);
+
__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)
@@ -1519,6 +1520,9 @@ 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);
@@ -1539,9 +1543,6 @@ 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
prev parent reply other threads:[~2021-04-13 5:48 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 5:47 [PATCH RFC v2 0/4] virtio net: spurious interrupt related fixes Michael S. Tsirkin
2021-04-13 5:47 ` [PATCH RFC v2 1/4] virtio: fix up virtio_disable_cb Michael S. Tsirkin
2021-04-13 8:51 ` Jason Wang
2021-04-13 14:01 ` Willem de Bruijn
2021-04-13 19:53 ` Michael S. Tsirkin
2021-04-13 21:44 ` Willem de Bruijn
2021-04-13 22:11 ` Michael S. Tsirkin
2021-04-14 0:24 ` Willem de Bruijn
2021-04-13 5:47 ` [PATCH RFC v2 2/4] virtio_net: disable cb aggressively Michael S. Tsirkin
2021-04-13 8:53 ` Jason Wang
2021-04-13 14:08 ` Willem de Bruijn
2021-04-13 14:33 ` Michael S. Tsirkin
2021-04-13 5:47 ` [PATCH RFC v2 3/4] virtio_net: move tx vq operation under tx queue lock Michael S. Tsirkin
2021-04-13 8:54 ` Jason Wang
2021-04-13 14:02 ` Michael S. Tsirkin
2021-04-13 14:20 ` Willem de Bruijn
2021-04-13 19:38 ` Michael S. Tsirkin
2021-04-13 5:47 ` Michael S. Tsirkin [this message]
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