lkml.org 
[lkml]   [2018]   [Jul]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [v2 PATCH 2/2] powerpc: Enable CPU_FTR_ASYM_SMT for interleaved big-cores
On Wed, Jul 04, 2018 at 01:45:05PM +0530, Gautham R Shenoy wrote:
> Hi Murilo,
>
> Thanks for the review.
>
> On Tue, Jul 03, 2018 at 02:53:46PM -0300, Murilo Opsfelder Araujo wrote:
> [..snip..]
>
> > > - /* Initialize CPU <=> thread mapping/
> > > + if (has_interleaved_big_core) {
> > > + int key = __builtin_ctzl(CPU_FTR_ASYM_SMT);
> > > +
> > > + cur_cpu_spec->cpu_features |= CPU_FTR_ASYM_SMT;
> > > + static_branch_enable(&cpu_feature_keys[key]);
> > > + pr_info("Detected interleaved big-cores\n");
> > > + }
> >
> > Shouldn't we use cpu_has_feature(CPU_FTR_ASYM_SMT) before setting
> > > it?
>
>
> Are you suggesting that we do the following?
>
> if (has_interleaved_big_core &&
> !cpu_has_feature(CPU_FTR_ASYM_SMT)) {
> ...
> }
>
> Currently CPU_FTR_ASYM_SMT is set at compile time for only POWER7
> where running the tasks on lower numbered threads give us the benefit
> of SMT thread folding. Interleaved big core is a feature introduced
> only on POWER9. Thus, we know that CPU_FTR_ASYM_SMT is not set in
> cpu_features at this point.

Since we're setting CPU_FTR_ASYM_SMT, it doesn't make sense to use
cpu_has_feature(CPU_FTR_ASYM_SMT). I thought cpu_has_feature() held all
available features (not necessarily enabled) that we could check before
setting or enabling such feature. I think I misread it. Sorry.

>
> >
> > > +
> > > + /* Initialize CPU <=> thread mapping/
> > > *
> > > * WARNING: We assume that the number of threads is the same for
> > > * every CPU in the system. If that is not the case, then some code
> > > --
> > > 1.9.4
> > >
> >
> > --
> > Murilo
>
> --
> Thanks and Regards
> gautham.
>

--
Murilo

\
 
 \ /
  Last update: 2018-07-04 19:37    [W:0.115 / U:1.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site