From: Jason Wang <jasowang@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>, linux-kernel@vger.kernel.org
Cc: Jakub Kicinski <kuba@kernel.org>, 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: Re: [PATCH v3 2/4] virtio_net: move txq wakeups under tx q lock
Date: Thu, 27 May 2021 11:48:33 +0800 [thread overview]
Message-ID: <30c69182-cc6c-3e45-1db9-5b061e43e1d6@redhat.com> (raw)
In-Reply-To: <20210526082423.47837-3-mst@redhat.com>
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;
> }
>
next prev parent reply other threads:[~2021-05-27 3:48 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-26 8:24 [PATCH v3 0/4] virtio net: spurious interrupt related fixes Michael S. Tsirkin
2021-05-26 8:24 ` [PATCH v3 1/4] virtio_net: move tx vq operation under tx queue lock Michael S. Tsirkin
2021-05-27 3:41 ` Jason Wang
2021-05-28 22:25 ` Willem de Bruijn
2021-06-09 22:03 ` Michael S. Tsirkin
2021-05-26 8:24 ` [PATCH v3 2/4] virtio_net: move txq wakeups under tx q lock Michael S. Tsirkin
2021-05-27 3:48 ` Jason Wang [this message]
2021-05-26 8:24 ` [PATCH v3 3/4] virtio: fix up virtio_disable_cb Michael S. Tsirkin
2021-05-27 4:01 ` Jason Wang
2023-03-30 6:07 ` Xuan Zhuo
2023-03-30 6:44 ` Michael S. Tsirkin
2023-03-30 6:54 ` Xuan Zhuo
2023-03-30 14:04 ` Michael S. Tsirkin
2023-03-31 3:38 ` Xuan Zhuo
2021-05-26 8:24 ` [PATCH v3 4/4] virtio_net: disable cb aggressively Michael S. Tsirkin
2021-05-26 15:15 ` Eric Dumazet
2021-05-26 21:22 ` Willem de Bruijn
2021-05-26 19:39 ` Jakub Kicinski
2021-05-27 4:09 ` Jason Wang
2023-01-16 13:41 ` Laurent Vivier
2023-01-17 3:48 ` Jason Wang
2021-05-26 15:34 ` [PATCH v3 0/4] virtio net: spurious interrupt related fixes Willem de Bruijn
2021-06-01 2:53 ` Willem de Bruijn
2021-06-09 21:36 ` Willem de Bruijn
2021-06-09 22:59 ` Willem de Bruijn
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