Re: [PATCH][ARM] Switch to default sched pressure algorithm

[Christophe Lyon <christophe.lyon@linaro.org>]

On Sat, 12 Oct 2019 at 02:52, Ramana Radhakrishnan
<ramana.gcc@googlemail.com> wrote:
>
> On Fri, Oct 11, 2019 at 6:19 PM Wilco Dijkstra <Wilco.Dijkstra@arm.com> wrote:
> >
> > Hi Ramana,
> >
> > > Can you see what happens with the Cortex-A8 or Cortex-A9 schedulers to
> > > spread the range across some v7-a CPUs as well ? While they aren't that popular today I
> > > would suggest you look at them because the defaults for v7-a are still to use the
> > > Cortex-A8 scheduler and the Cortex-A9 scheduler might well also get used in places given
> > > the availability of hardware.
> >
> > The results are practically identical to Cortex-A53 and A57 - there is a huge codesize win
> > across the board on SPEC2006, there isn't a single benchmark that is larger (ie. more
> > spilling).
> >
> > > I'd be happy to move this forward if you could show if there is no *increase* in spills
> > > for the same range of benchmarks that you are doing for the Cortex-A8 and Cortex-A9
> > > schedulers.
> >
> > There certainly isn't. I don't think results like these could be any more one-sided, it's a
> > significant win for every single benchmark, both for codesize and performance!
> >
>
> Ok go ahead - please be sensitive to testsuite regressions.
>

Hi Wilco,

I've noticed that your patch caused a regression:
FAIL: gcc.dg/tree-prof/pr77698.c scan-rtl-dump-times alignments
"internal loop alignment added" 1

Christophe


when the compiler is configured --with-mode thumb (or forcing -mthumb
when running the tests)
> Ramana
>
>
> > What isn't clear is whether something has gone horribly wrong in the scheduler which
> > could be fixed/reverted, but as it is right now I can't see it being useful at all. This means
> > we should also reevaluate whether pressure scheduling now hurts AArch64 too.
> >
> > Cheers,
> > Wilco