Re: [PATCH v2 2/2] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to MM CPUs

ypodemsk
2023-06-26T14:37:30Z

On Thu, 2023-06-22 at 06:37 -0700, Dave Hansen wrote:
> On 6/22/23 06:14, ypodemsk@redhat.com wrote:
> > I will send a new version with the local variable as you suggested
> > soon.
> > As for the config name, what about CONFIG_ARCH_HAS_MM_CPUMASK?
>
> The confusing part about that name is that mm_cpumask() and
> mm->cpu_bitmap[] are defined unconditionally. So, they're *around*
> unconditionally but just aren't updated.
>
I think your right about the config name,
How about the
CONFIG_ARCH_USE_MM_CPUMASK?
This has the right semantic as these archs use the cpumask field of the
mm struct.

> BTW, it would also be nice to have _some_ kind of data behind this
> patch.
>
> Fewer IPIs are better I guess, but it would still be nice if you
> could say:
>
> Before this patch, /proc/interrupts showed 123 IPIs/hour for an
> isolated CPU. After the approach here, it was 0.
>
> ... or something.

This is part of an ongoing effort to remove IPIs and this one was found
via code inspection.