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 4/4] virtio_net: disable cb aggressively
Date: Thu, 27 May 2021 12:09:31 +0800 [thread overview]
Message-ID: <93ed586a-d805-2fda-60e7-68eca9e8ac97@redhat.com> (raw)
In-Reply-To: <20210526082423.47837-5-mst@redhat.com>
在 2021/5/26 下午4:24, Michael S. Tsirkin 写道:
> There are currently two cases where we poll TX vq not in response to a
> callback: start xmit and rx napi. We currently do this with callbacks
> enabled which can cause extra interrupts from the card. Used not to be
> a big issue as we run with interrupts disabled but that is no longer the
> case, and in some cases the rate of spurious interrupts is so high
> linux detects this and actually kills the interrupt.
>
> Fix up by disabling the callbacks before polling the tx vq.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> drivers/net/virtio_net.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index c29f42d1e04f..a83dc038d8af 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1433,7 +1433,10 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
> return;
>
> if (__netif_tx_trylock(txq)) {
> - free_old_xmit_skbs(sq, true);
> + do {
> + virtqueue_disable_cb(sq->vq);
> + free_old_xmit_skbs(sq, true);
> + } while (unlikely(!virtqueue_enable_cb_delayed(sq->vq)));
>
> if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
> netif_tx_wake_queue(txq);
> @@ -1605,12 +1608,17 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum);
> bool kick = !netdev_xmit_more();
> bool use_napi = sq->napi.weight;
> + unsigned int bytes = skb->len;
>
> /* Free up any pending old buffers before queueing new ones. */
> - free_old_xmit_skbs(sq, false);
> + do {
> + if (use_napi)
> + virtqueue_disable_cb(sq->vq);
>
> - if (use_napi && kick)
> - virtqueue_enable_cb_delayed(sq->vq);
> + free_old_xmit_skbs(sq, false);
> +
> + } while (use_napi && kick &&
> + unlikely(!virtqueue_enable_cb_delayed(sq->vq)));
>
> /* timestamp packet in software */
> skb_tx_timestamp(skb);
I wonder whehter we can simple disable cb during ndo_start_xmit(), or is
there a way to make xmit and napi work in parallel?
Thanks
next prev parent reply other threads:[~2021-05-27 4:09 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
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 [this message]
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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