On Thu, 2023-06-22 at 06:37 -0700, Dave Hansen wrote:

On 6/22/23 06:14, ypodemsk@redhat.com wrote:

quoted

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.