Re: [PATCH] virtio_net: suppress cpu stall when free_unused_bufs

[Wenliang Wang]

On 4/27/23 2:20 PM, Xuan Zhuo wrote:
> On Thu, 27 Apr 2023 12:34:33 +0800, Wenliang Wang <wangwenliang.1995@xxxxxxxxxxxxx> wrote:
> > For multi-queue and large rx-ring-size use case, the following error
>
> Cound you give we one number for example?

128 queues and 16K queue_size is typical.

> > occurred when free_unused_bufs:
> > rcu: INFO: rcu_sched self-detected stall on CPU.
> >
> > Signed-off-by: Wenliang Wang <wangwenliang.1995@xxxxxxxxxxxxx>
> > ---
> >   drivers/net/virtio_net.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index ea1bd4bb326d..21d8382fd2c7 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -3565,6 +3565,7 @@ static void free_unused_bufs(struct virtnet_info *vi)
> >   		struct virtqueue *vq = vi->rq[i].vq;
> >   		while ((buf = virtqueue_detach_unused_buf(vq)) != NULL)
> >   			virtnet_rq_free_unused_buf(vq, buf);
> > +		schedule();
>
> Just for rq?
>
> Do we need to do the same thing for sq?
Rq buffers are pre-allocated, take seconds to free rq unused buffers.

Sq unused buffers are much less, so do the same for sq is optional.

> Thanks.
>
>
> >   	}
> >   }
> >
> > --
> > 2.20.1