Re: [PATCH 1/3] perf: Add macros to specify onchip L2/L3 accesses

[Michael Ellerman <mpe@ellerman.id.au>]

Peter Zijlstra <peterz@infradead.org> writes:
> On Tue, Sep 14, 2021 at 08:40:38PM +1000, Michael Ellerman wrote:
>> Peter Zijlstra <peterz@infradead.org> writes:
>
>> > I'm thinking we ought to keep hops as steps along the NUMA fabric, with
>> > 0 hops being the local node. That only gets us:
>> >
>> >  L2, remote=0, hops=HOPS_0 -- our L2
>> >  L2, remote=1, hops=HOPS_0 -- L2 on the local node but not ours
>> >  L2, remote=1, hops!=HOPS_0 -- L2 on a remote node
>> 
>> Hmm. I'm not sure about tying it directly to NUMA hops. I worry we're
>> going to see more and more systems where there's a hierarchy within the
>> chip/package, in addition to the traditional NUMA hierarchy.
>> 
>> Although then I guess it becomes a question of what exactly is a NUMA
>> hop, maybe the answer is that on those future systems those
>> intra-chip/package hops should be represented as NUMA hops.
>> 
>> It's not like we have a hard definition of what a NUMA hop is?
>
> Not really, typically whatever the BIOS/DT/whatever tables tell us. I
> think in case of Power you're mostly making things up in software :-)

Firmware is software so yes :)

> But yeah, I think we have plenty wriggle room there.

OK.

cheers