linux-kernel - Re: [PATCH v4 2/2] io_uring: Add support for napi_busy

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Date:   Wed, 02 Mar 2022 17:03:58 -0500
From:   Olivier Langlois <olivier@...llion01.com>
To:     Hao Xu <haoxu@...ux.alibaba.com>, Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>
Cc:     io-uring <io-uring@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/2] io_uring: Add support for napi_busy_poll

On Wed, 2022-03-02 at 14:38 +0800, Hao Xu wrote:
> > > 
> > > 
> > > If that is what you suggest, what would this info do for the
> > > caller?
> > > 
> > > IMHO, it wouldn't help in any way...
> > 
> > Hmm, I'm not sure, you're probably right based on that ENOMEM here 
> > shouldn't
> > 
> > fail the arm poll, but we wanna do it, we can do something like
> > what 
> > we do for
>                              ^---but if we wanna do it
My position is that being able to perform busy poll is a nice to have
feature if the necessary resources are available. If not the request
will still be handled correctly so nothing special should be done in
case of mem alloc problem.

but fair enough, lets wait for Jens and Pavel to chime him if they
would like to see something to be done here.

Beside that, all I need to know is if napi_list needs to be protected
in __io_sq_thread with regards to io worket threads to start working on
a v5.

I'll look into this question too...