Re: [RFC][PATCH 00/26] sched/numa

Peter Zijlstra
2012-03-19T12:21:16Z

On Mon, 2012-03-19 at 13:42 +0200, Avi Kivity wrote:
> It's the standard space/time tradeoff. Once solution wants more
> storage, the other wants more faults.
>
> Note scanners can use A/D bits which are cheaper than faults.

I'm not convinced.. the scanner will still consume time even if the
system is perfectly balanced -- it has to in order to determine this.

So sure, A/D/other page table magic can make scanners faster than faults
however you only need faults when you're actually going to migrate a
task. Whereas you always need to scan, even in the stable state.

So while the per-instance times might be in favour of scanning, I'm
thinking the accumulated time is in favour of faults.