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.
