On Thu, Jul 20, 2023 at 08:31:13AM -0700, Shannon Nelson wrote:
> On 7/20/23 1:38 AM, Jason Wang wrote:
> >
> > Adding cond_resched() to the command waiting loop for a better
> > co-operation with the scheduler. This allows to give CPU a breath to
> > run other task(workqueue) instead of busy looping when preemption is
> > not allowed on a device whose CVQ might be slow.
> >
> > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> > ---
> > drivers/net/virtio_net.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 9f3b1d6ac33d..e7533f29b219 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -2314,8 +2314,10 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
> > * into the hypervisor, so the request should be handled immediately.
> > */
> > while (!virtqueue_get_buf(vi->cvq, &tmp) &&
> > - !virtqueue_is_broken(vi->cvq))
> > + !virtqueue_is_broken(vi->cvq)) {
> > + cond_resched();
> > cpu_relax();
> > + }
>
> The cover letter suggests that this addresses the infinite poll for buggy
> devices, but I don't see how that is resolved here. This should make it a
> little nicer to the system, but it still is going to poll forever on a
> device that has gone catatonic. Is there a reason that I'm missing that we
> don't have a polling limit here?
>
> sln
we don't know what the limit would be. but given it's a workqueue
now, why does it still have to poll as opposed to blocking?
> >
> > return vi->ctrl->status == VIRTIO_NET_OK;
> > }
> > --
> > 2.39.3
> >
> > _______________________________________________
> > Virtualization mailing list
> > Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
> > https://lists.linuxfoundation.org/mailman/listinfo/virtualization
_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
