Re: [Xen-devel] [RFC Design Doc] Intel L2 Cache Allocation Technology (L2 CAT) Feature enabling

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.05.16 at 08:26, <he.chen@xxxxxxxxxxxxxxx> wrote:
> On Thu, May 12, 2016 at 04:05:36AM -0600, Jan Beulich wrote:
>> >>> On 12.05.16 at 11:40, <he.chen@xxxxxxxxxxxxxxx> wrote:
>> > We plan to bring new PQoS feature called Intel L2 Cache Allocation
>> > Technology (L2 CAT) to Xen.
>> > 
>> > L2 CAT is supported on Atom codename Goldmont and beyond. “Big-core”
>> > Xeon does not support L2 CAT in current generations.
>> 
>> Looks mostly like a direct (and hence reasonable) extension of what
>> we have for L3 right now. One immediate question I have is whether
>> tying this to per-socket information is a good idea. As soon as Xeon-s
>> would also gain such functionality, things would (aiui) need to become
>> per-core (as L2 is per core there iirc).
>> 
> 
> L2 Cache capability keeps the same through all cores in a socket, so we
> make it per-socket to balance code complexity and accessibility.
> 
> I am not a expert in scheduler, do you mean in some cases, a domain
> would apply different L2 cache access pattern when it is scheduled on
> different cores even though the cores are in the same socket?

No, I mean different domains may be running on different cores,
and hence different policies may be needed to accommodate them
all.

Jan

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