Re: [RFC][PATCH 25/26] sched, numa: Only migrate long-running entities

Peter Zijlstra
2012-07-09T14:56:37Z

On Mon, 2012-07-09 at 10:53 -0400, Rik van Riel wrote:
> On 07/09/2012 08:26 AM, Peter Zijlstra wrote:
> > On Sun, 2012-07-08 at 14:34 -0400, Rik van Riel wrote:
>
> >> Do we really want to calculate the amount of CPU time used
> >> by a process, and start migrating after just one second?
> >>
> >> Or would it be ok to start migrating once a process has
> >> been scanned once or twice by the NUMA code?
> >
> > You mean, the 2-3rd time we try and migrate this task, not the memory
> > scanning thing as per Andrea, right?
>
> Indeed. That way we can simply keep a flag somewhere,
> instead of iterating over the threads in a process.

Note that the code in -tip needs to iterate over all tasks in order to
test all cpus_allowed and mems_allowed masks. But we could keep a
process wide intersection of those masks around as well I guess,
updating them is a slow path anyway.