Re: [PATCH net 1/3] virtio-net: make refill work a per receive queue work

[Jason Wang]

On Wed, Dec 24, 2025 at 9:48 AM Michael S. Tsirkin <m...@redhat.com> wrote:
>
> On Wed, Dec 24, 2025 at 09:37:14AM +0800, Xuan Zhuo wrote:
> >
> > Hi Jason,
> >
> > I'm wondering why we even need this refill work. Why not simply let NAPI 
> > retry
> > the refill on its next run if the refill fails? That would seem much 
> > simpler.
> > This refill work complicates maintenance and often introduces a lot of
> > concurrency issues and races.
> >
> > Thanks.
>
> refill work can refill from GFP_KERNEL, napi only from ATOMIC.
>
> And if GFP_ATOMIC failed, aggressively retrying might not be a great idea.

Btw, I see some drivers are doing things as Xuan said. E.g
mlx5e_napi_poll() did:

busy |= INDIRECT_CALL_2(rq->post_wqes,
                                mlx5e_post_rx_mpwqes,
                                mlx5e_post_rx_wqes,

...

if (busy) {
         if (likely(mlx5e_channel_no_affinity_change(c))) {
                work_done = budget;
                goto out;
...

>
> Not saying refill work is a great hack, but that is the reason for it.
> --
> MST
>

Thanks