Re: [PATCH] riscv: Fix build with CONFIG_CC_OPTIMIZE_FOR_SIZE=y

Conor Dooley
2022-10-04T17:15:32Z

On Tue, Oct 04, 2022 at 09:52:41AM -0700, Atish Patra wrote:
> On Sat, Oct 1, 2022 at 1:13 PM Conor Dooley <conor@kernel.org> wrote:

> > > Thanks. It would be good to understand what happens when "pause" is
> > > executed on these boards ?
> >
> > The actual pause instruction? uhh, so with the usual "I don't know what
> > I am doing" disclaimer, I ran each of the .insn and pause instruction 48
> > times in a row and checked the time elapsed via rdcycle & then ran that
> > c program 1000 times in a bash loop. Got the below, the insns were run
> > first and then the pauses.
> > insn pause
> > min 2.3 3.2
> > max 9.5 10.6
> > avg 27.0 29.1
> > 5% 2.9 4.2
> > 95% 18.1 19.1
> >
> > Swapping the pause & insn order around made a minor difference, but not
> > enough to report on. I'd be very wary of drawing any real conclusions
> > from this data, but at least both are roughly similar (and certainly not
> > even close to doing the div w/ zero args.
> >
>
> Yeah. That's what I was expecting. So we can't drop the div for now. Otherwise,
> the existing hardware(don't support Zhintpause) suffers by spinning faster.
>
> Thanks for running the experiments.

I've lost track, does that mean the patch is okay as, is or needs to be
changed? The former, right?

Thanks,
Conor.