RE: [PATCH 3/9] x86/intel_rdt: Cache Allocation documentation and cgroup usage guide

[Vikas Shivappa]

On Tue, 28 Jul 2015, Auld, Will wrote:

> > -----Original Message-----
> >
> > Same comment as above - Cgroup masks can always overlap and other cgroups
> > can allocate the same cache , and hence wont have exclusive cache allocation.
>
> [Auld, Will] You can define all the cbm to provide one clos with an exclusive area

Do you mean a CLOS that has all the bits set. We donot support exclusive area 
today. The bits in the mask can overlap .. hence can always share the same cache 
allocation .

> > So natuarally the cgroup with tasks would get to use the cache if it has the same
> > mask (say representing 50% of cache in your example) as others .
>
> [Auld, Will] automatic adjustment of the cbm make me nervous. There are times
> when we want to limit the cache for a process independent of whether there is
> lots of unused cache.

Please see example below - In general , I just mean the cache mask can have bits 
that can overlap - does not matter whether there is tasks in it or not.

> > (assume there are 8 bits max cbm)
> > cgroupa - mask - 0xf
> > cgroupb - mask - 0xf . Now if cgroupa has no tasks , cgroupb naturally gets all
> > the cache.
> >
> > Thanks,
> > Vikas
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