From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: Jason Wang <jasowang@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Jakub Kicinski <kuba@kernel.org>, Wei Wang <weiwan@google.com>,
David Miller <davem@davemloft.net>,
Network Development <netdev@vger.kernel.org>,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH RFC v2 2/4] virtio_net: disable cb aggressively
Date: Tue, 13 Apr 2021 10:08:34 -0400 [thread overview]
Message-ID: <CA+FuTSdt6udHb7V4Xcj=OQ3M-iRazgOMWJinCbLJyof=ttB=Cw@mail.gmail.com> (raw)
In-Reply-To: <43db5c1e-9908-55bb-6d1a-c6c8d71e2315@redhat.com>
On Tue, Apr 13, 2021 at 4:53 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> 在 2021/4/13 下午1:47, 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 | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 82e520d2cb12..16d5abed582c 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -1429,6 +1429,7 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
> > return;
> >
> > if (__netif_tx_trylock(txq)) {
> > + virtqueue_disable_cb(sq->vq);
> > free_old_xmit_skbs(sq, true);
> > __netif_tx_unlock(txq);
>
>
> Any reason that we don't need to enable the cb here?
This is an opportunistic clean outside the normal tx-napi path, so if
disabling the tx interrupt here, it won't be reenabled based on
napi_complete_done.
I think that means that it stays disabled until the following start_xmit:
if (use_napi && kick)
virtqueue_enable_cb_delayed(sq->vq);
But that seems sufficient.
next prev parent reply other threads:[~2021-04-13 14:09 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 [this message]
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 ` [PATCH RFC v2 4/4] virtio_net: move txq wakeups under tx q lock Michael S. Tsirkin
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