Re: [PATCH v2 0/2] sched/topology: optimize topology_span_sane()

From: Yury Norov
Date: Wed Aug 28 2024 - 10:10:11 EST


Ping again?

On Wed, Aug 14, 2024 at 09:35:04AM -0700, Yury Norov wrote:
> Ping?
>
> On Wed, Aug 07, 2024 at 12:05:19PM -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:
> > - defer initialization of 'mc' in patch #1 @Chen Yu;
> > - more comments from Valentin Schneider.
> >
> >
> > Yury Norov (2):
> > sched/topology: pre-compute topology_span_sane() loop params
> > sched/topology: optimize topology_span_sane()
> >
> > kernel/sched/topology.c | 20 ++++++++++++++++++--
> > 1 file changed, 18 insertions(+), 2 deletions(-)
> >
> > --
> > 2.43.0