linux-kernel - Re: [PATCH] sched/topology: Assert non-NUMA topology masks don't (partially) overlap

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Date:   Thu, 16 Jan 2020 16:19:42 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     linux-kernel@...r.kernel.org, sudeep.holla@....com,
        prime.zeng@...ilicon.com, dietmar.eggemann@....com,
        morten.rasmussen@....com, mingo@...nel.org
Subject: Re: [PATCH] sched/topology: Assert non-NUMA topology masks don't
 (partially) overlap

On Thu, Jan 16, 2020 at 11:44:28AM +0100, Peter Zijlstra wrote:
> On Wed, Jan 15, 2020 at 04:09:15PM +0000, Valentin Schneider wrote:
> > @@ -1975,6 +2011,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
> >  				has_asym = true;
> >  			}
> >  
> > +			if (WARN_ON(!topology_span_sane(tl, cpu_map, i)))
> > +				goto error;
> > +
> >  			sd = build_sched_domain(tl, cpu_map, attr, sd, dflags, i);
> >  
> >  			if (tl == sched_domain_topology)
> 
> This is O(nr_cpus), but then, that function already is, so I don't see a
> problem with this.

Clearly I meant to write O(nr_cpus^2), there's a bunch of nested
for_each_cpu() in there.

> I'll take it, thanks!