Re: [PATCH v5] fs: Improve eventpoll logging to stop indicting timerfd

[Isaac Manjarres <isaacmanjarres@google.com>]

On Mon, Jun 24, 2024 at 11:03:43AM -0700, John Stultz wrote:
> On Thu, Jun 6, 2024 at 10:28 AM 'Isaac J. Manjarres' via kernel-team
> <kernel-team@android.com> wrote:
> >
> > From: Manish Varma <varmam@google.com>
> >
> > timerfd doesn't create any wakelocks, but eventpoll can.  When it does,
> > it names them after the underlying file descriptor, and since all
> > timerfd file descriptors are named "[timerfd]" (which saves memory on
> > systems like desktops with potentially many timerfd instances), all
> > wakesources created as a result of using the eventpoll-on-timerfd idiom
> > are called... "[timerfd]".
> >
> > However, it becomes impossible to tell which "[timerfd]" wakesource is
> > affliated with which process and hence troubleshooting is difficult.
> 
> While your explanation above is understandable, I feel like it might
> benefit from a more concrete example to show why this is problematic?
> It feels like the description gets into the weeds pretty quickly and
> makes it hard to understand the importance of the change.

> 
> Again the N:P.F mapping is clear, but maybe including a specific
> before and after example would help?
> 
> Additionally, once you have this better named wakesource, can you
> provide a specific example to illustrate a bit on how this
> specifically helps the troubleshooting that was difficult before?
> 
> thanks
> -john

Hi John,

Thanks for your feedback on this! I'm more than happy to add more
details to the commit text. I'll go ahead and add an example to
showcase a scenario where the proposed changes make debugging easier.

I'll send out v6 of the patch soon.

--Isaac