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    SubjectRe: [PATCH v3] x86,sched: allow topologies where NUMA nodes share an LLC
    On Thu, Mar 29, 2018 at 07:37:29AM -0700, Dave Hansen wrote:
    > On 03/29/2018 06:47 AM, Peter Zijlstra wrote:
    > > Further I think Dave argued that we should not change the llc-size,
    > > because while SNC presents a subset of the cache to local CPUs, for
    > > remote data the whole cache is still available, again something some
    > > applications might rely on.
    >
    > BTW, I may have argued this in the past, but I don't think it's the best
    > thing to do.
    >
    > If anything, we should optimize for the _users_ of this information: the
    > performance-sensitive ones who are digging up the cache topology. They
    > are also likely to be the most NUMA-affinitized and stay node-local with
    > much of their memory traffic. That would seem to point us in the
    > direction of enumerating two separate, half-sized LLCs "shared" only by
    > the slice when SNC mode is on.
    >
    > That's what I've argued to the hardware folks lately, at least.

    Fair enough; then we need change the reported cache-size and mention all
    this in (preferably) both comment and Changelog.

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