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Date: Mon, 18 Jul 2022 23:37:47 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Yury Norov <yury.norov@...il.com> Cc: linux-kernel@...r.kernel.org, Alexander Lobakin <alexandr.lobakin@...el.com>, Alexei Starovoitov <ast@...nel.org>, Alexey Klimov <aklimov@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, Andrii Nakryiko <andrii@...nel.org>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Ben Segall <bsegall@...gle.com>, Christoph Lameter <cl@...ux.com>, Dan Williams <dan.j.williams@...el.com>, Daniel Borkmann <daniel@...earbox.net>, Daniel Bristot de Oliveira <bristot@...hat.com>, Dennis Zhou <dennis@...nel.org>, Dietmar Eggemann <dietmar.eggemann@....com>, Eric Dumazet <edumazet@...gle.com>, Frederic Weisbecker <fweisbec@...il.com>, Guenter Roeck <linux@...ck-us.net>, Ingo Molnar <mingo@...hat.com>, Isabella Basso <isabbasso@...eup.net>, John Fastabend <john.fastabend@...il.com>, Josh Poimboeuf <jpoimboe@...nel.org>, Juergen Gross <jgross@...e.com>, Juri Lelli <juri.lelli@...hat.com>, KP Singh <kpsingh@...nel.org>, Kees Cook <keescook@...omium.org>, Martin KaFai Lau <kafai@...com>, Mel Gorman <mgorman@...e.de>, Miroslav Benes <mbenes@...e.cz>, Nathan Chancellor <nathan@...nel.org>, "Paul E . McKenney" <paulmck@...nel.org>, Randy Dunlap <rdunlap@...radead.org>, Rasmus Villemoes <linux@...musvillemoes.dk>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Song Liu <songliubraving@...com>, Steven Rostedt <rostedt@...dmis.org>, Tejun Heo <tj@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Valentin Schneider <vschneid@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, Vlastimil Babka <vbabka@...e.cz>, Yonghong Song <yhs@...com>, linux-mm@...ck.org, netdev@...r.kernel.org, bpf@...r.kernel.org Subject: Re: [PATCH 15/16] sched/topology: optimize topology_span_sane() On Mon, Jul 18, 2022 at 12:28:43PM -0700, Yury Norov wrote: > kernel/sched/topology.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index 05b6c2ad90b9..ad32d0a43424 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -2211,6 +2211,8 @@ static struct sched_domain *build_sched_domain(struct sched_domain_topology_leve > static bool topology_span_sane(struct sched_domain_topology_level *tl, > const struct cpumask *cpu_map, int cpu) > { > + const struct cpumask *mc = tl->mask(cpu); > + const struct cpumask *mi; > int i; > > /* NUMA levels are allowed to overlap */ > @@ -2226,14 +2228,18 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl, > for_each_cpu(i, cpu_map) { > if (i == cpu) > continue; > + > + mi = tl->mask(i); > + if (mi == mc) > + continue; > + > /* > * We should 'and' all those masks with 'cpu_map' to exactly > * match the topology we're about to build, but that can only > * remove CPUs, which only lessens our ability to detect > * overlaps > */ > - if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) && > - cpumask_intersects(tl->mask(cpu), tl->mask(i))) > + if (!cpumask_equal(mc, mi) && cpumask_intersects(mc, mi)) > return false; > } This is once again a super slow path; but I don't suppose you're making the code worse in this case.
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