Re: [PATCH v7 01/15] sched/core: uclamp: Add CPU's clamp buckets refcounting

Peter Zijlstra
2019-03-14T19:18:49Z

On Thu, Mar 14, 2019 at 03:07:53PM +0000, Patrick Bellasi wrote:
> On 14-Mar 14:32, Peter Zijlstra wrote:
> > On Thu, Mar 14, 2019 at 12:13:15PM +0000, Patrick Bellasi wrote:
> > > > I'd be most impressed if they pull this off. Check the generated code
> > > > and see I suppose :-)
> > >
> > > On x86 the code generated looks exactly the same:
> > >
> > > https://godbolt.org/z/PjmA7k
> >
> > Argh, they do mult by inverse to avoid the division, and can do this
> > because its a constant.
> >
> > And then yes, your arm version looks worse.
>
> your "arm version" is worst then x86, or "your version" is worse?
>
> IOW, should I keep the code as the original? Do you prefer your
> version? Or... we don't really care...

Yeah, keep the original, it didn't matter on x86 and arm regressed with
my version.

> > It does what I expected with -Os, but as Rutland said the other day,
> > that stands for Optimize for Sadness.
>
> Yes, I guess we cannot optimize for all flags... however, just let me
> know what you prefer and I'll put that version in ;)

Yeah, don't bother optimizing for -Os, it generally creates atrocious
crap, hence Rutland calling it 'Optimize for Sadness'.