Re: [PATCH] SN2 user-MMIO CPU migration

Ingo Molnar
2006-01-24T09:02:35Z

* Brent Casavant <bcasavan@sgi.com> wrote:

> I agree with him that it's not wonderful to hook into mainline
> scheduler code to solve this, but the alternative is what I presented
> here: check if old CPU = new CPU at each context switch-in, entirely
> within IA64 code.

what's the problem with doing that? It's a single comparison [of two
values we already have accessed in that function!] and a rarely taken
branch in a single subarch of a single arch's switch_to() function. If
this use (of migration related arch functionality) becomes more
widespread then we can generalize it, but right now i just dont see the
point, given that the two solutions are almost totally equivalent in
terms of "overhead".

Ingo