Re: Cache Allocation Technology Design

Peter Zijlstra
2014-11-10T15:50:15Z

On Thu, Nov 06, 2014 at 05:03:23PM +0000, Matt Fleming wrote:
> On Tue, 04 Nov, at 02:17:14PM, Peter Zijlstra wrote:
> >
> > I don't like extending cpusets further. Its already a weird and too big
> > controller.
> >
> > What is wrong with having a specific CQM controller and using it
> > together with cpusets where desired?
>
> The specific problem that conflating cpusets and the CAT controller is
> trying to solve is that on some platforms the CLOS ID doesn't move with
> data that travels up the cache hierarchy, i.e. we lose the CLOS ID when
> data moves from LLC to L2.
>
> I think the idea with pinning CLOS IDs to a specific cpu and any tasks
> that are using that ID is that it works around this problem out of the
> box, rather than requiring sysadmins to configure things.

So either the user needs to set that mode _and_ set cpu masks, or the
user needs to use cpusets and set masks, same difference to me.