Re: [PATCH v3 0/3] sched/topology: optimize topology_span_sane()
From: Yury Norov
Date: Mon Sep 30 2024 - 15:15:17 EST
Ping again?
On Sat, Sep 14, 2024 at 09:54:43AM -0700, Yury Norov wrote:
> Ping?
>
> On Mon, Sep 02, 2024 at 11:36:04AM -0700, Yury Norov wrote:
> > The function may call cpumask_equal with tl->mask(cpu) == tl->mask(i),
> > even when cpu != i. In such case, cpumask_equal() would always return
> > true, and we can proceed to the next iteration immediately.
> >
> > Valentin Schneider shares on it:
> >
> > PKG can potentially hit that condition, and so can any
> > sched_domain_mask_f that relies on the node masks...
> >
> > I'm thinking ideally we should have checks in place to
> > ensure all node_to_cpumask_map[] masks are disjoint,
> > then we could entirely skip the levels that use these
> > masks in topology_span_sane(), but there's unfortunately
> > no nice way to flag them... Also there would be cases
> > where there's no real difference between PKG and NODE
> > other than NODE is still based on a per-cpu cpumask and
> > PKG isn't, so I don't see a nicer way to go about this.
> >
> > v1: https://lore.kernel.org/lkml/ZrJk00cmVaUIAr4G@yury-ThinkPad/T/
> > v2: https://lkml.org/lkml/2024/8/7/1299
> > v3:
> > - add topology_cpumask_equal() helper in #3;
> > - re-use 'cpu' as an iterator int the for_each_cpu() loop;
> > - add proper versioning for all patches.
> >
> > Yury Norov (3):
> > sched/topology: pre-compute topology_span_sane() loop params
> > sched/topology: optimize topology_span_sane()
> > sched/topology: reorganize topology_span_sane() checking order
> >
> > kernel/sched/topology.c | 29 +++++++++++++++++++++++++----
> > 1 file changed, 25 insertions(+), 4 deletions(-)
> >
> > --
> > 2.43.0