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

[Christophe JAILLET]

Le 28/08/2024 à 16:09, Yury Norov a écrit :
> Ping again?

Hi,

The covert letter is v2, but the patch below it are without v2.

In patch 1/2, the Suggested-by: tags in v1 have been removed in this new 
version :(.

CJ

> 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