Re: [RFC PATCH v2 12/17] sched: A quick and dirty cgroup tagging interface

[Phil Auld]

On Fri, Apr 26, 2019 at 04:13:07PM +0200 Peter Zijlstra wrote:
> On Thu, Apr 25, 2019 at 10:26:53AM -0400, Phil Auld wrote:
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index e8e5f26db052..b312ea1e28a4 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -7541,6 +7541,9 @@ static int cpu_core_tag_write_u64(struct cgroup_subsys_state *css, struct cftype
> >         if (val > 1)
> >                 return -ERANGE;
> >  
> > +       if (num_online_cpus() <= 1) 
> > +               return -EINVAL;
> 
> We actually know if there SMT on the system or not, which is much better
> indication still:
> 
> 	if (!static_branch_likely(&sched_smt_present))
> 		return -EINVAL;
> 
> >         if (tg->tagged == !!val)
> >                 return 0;
> >  
> > 
> > 
> > 
> > -- 

Yeah, I thought there was probably a better check.

Thanks!

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