netdev - Re: [PATCH net-next v3 1/5] net: implement threaded-able napi poll loop support

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Date:   Sat, 21 Nov 2020 18:23:33 -0800
From:   Wei Wang <weiwan@...gle.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Felix Fietkau <nbd@....name>, Paolo Abeni <pabeni@...hat.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Hillf Danton <hdanton@...a.com>
Subject: Re: [PATCH net-next v3 1/5] net: implement threaded-able napi poll
 loop support

On Sat, Nov 21, 2020 at 4:31 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Wed, 18 Nov 2020 11:10:05 -0800 Wei Wang wrote:
> > +int napi_set_threaded(struct napi_struct *n, bool threaded)
> > +{
> > +     ASSERT_RTNL();
> > +
> > +     if (n->dev->flags & IFF_UP)
> > +             return -EBUSY;
> > +
> > +     if (threaded == !!test_bit(NAPI_STATE_THREADED, &n->state))
> > +             return 0;
> > +     if (threaded)
> > +             set_bit(NAPI_STATE_THREADED, &n->state);
> > +     else
> > +             clear_bit(NAPI_STATE_THREADED, &n->state);
>
> Do we really need the per-NAPI control here? Does anyone have use cases
> where that makes sense? The user would be guessing which NAPI means
> which queue and which bit, currently.

Thanks for reviewing this.
I think one use case might be that if the driver uses separate napi
for tx and rx, one might want to only enable threaded mode for rx, and
leave tx completion in interrupt mode.


>
> > +     /* if the device is initializing, nothing todo */
> > +     if (test_bit(__LINK_STATE_START, &n->dev->state))
> > +             return 0;
> > +
> > +     napi_thread_stop(n);
> > +     napi_thread_start(n);
> > +     return 0;
> > +}
> > +EXPORT_SYMBOL(napi_set_threaded);
>
> Why was this exported? Do we still need that?
>

Yea. I guess it is not needed.

> Please rejig the patches into a reviewable form. You can use the
> Co-developed-by tag to give people credit on individual patches.

Will do. Thanks!