Re: [PATCH] kbuild: AutoFDO: Enable -salvage-stale-profile

[Nick Desaulniers]

On Thu, Nov 5, 2026 at 1:30 PM Doug Anderson <dianders@xxxxxxxxxxxx> wrote:
>
> Hi,
>
> On Thu, Nov 5, 2026 at 10:23 AM Rong Xu <xur@xxxxxxxxxx> wrote:
> >
> > 2.  The recommended usage model for kernel AutoFDO (as documented) is
> > to use the same source. While it might help in an iterative build
> > model, I don't see a strong reason to use it if there is no source
> > drift.
>
> Hmmm. I guess in the purist sense we'd want the AudoFDO profile to be
> for the exact source. ...but from my experience, that's not what
> happens in reality. If nothing else, developers locally working on the

Right. Rong's recommendation makes sense from a google3 perspective
(who I suspect is continuously regenerating profile data), but isn't
feasible for Android or ChromeOS (who are not).

> kernel still want to keep the AutoFDO optimizations so they're testing
> as close to what's in the field as possible. However, the act of
> working on the kernel will touch _some_ of the source. Keeping AFDO
> working as much as possible seems nice to me. Of course, I'm by no
> means an AutoFDO expert and mostly just got dragged into this issue,
> so happy to defer to the experts. ;-)
>
> -Doug



-- 
Thanks,
~Nick Desaulniers