On Mon, Jan 06, 2014 at 09:48:29PM +0000, Waskiewicz Jr, Peter P wrote: > On Mon, 2014-01-06 at 22:26 +0100, Peter Zijlstra wrote: > > On Mon, Jan 06, 2014 at 08:10:45PM +0000, Waskiewicz Jr, Peter P wrote: > > > There is one per logical CPU. However, in the current generation, they > > > report on the usage of the same L3 cache. But the CPU takes care of the > > > resolution of which MSR write and read comes from the logical CPU, so > > > software doesn't need to lock access to it from different CPUs. > > > > What are the rules of RMIDs, I can't seem to find that in the SDM and I > > think you're tagging cachelines with them. Which would mean that in > > order to (re) use them you need a complete cache (L3) wipe. > > The cacheline is tagged internally with the RMID as part of the waymask > for the thread in the core. > > > Without a wipe you keep having stale entries of the former user and no > > clear indication on when your numbers are any good. > > That can happen, yes. If you have leftover cache data from a process > that died that hasn't been evicted yet and it's assigned to the RMID > you're using, you will see its included cache occupancy to the overall > numbers. > > > Also, is there any sane way of shooting down the entire L3? > > That is a question I'd punt to hpa, but I'll ask him. Looking around > though, a WBINVD would certainly nuke things, but would hurt > performance. We could get creative with INVPCID as a process dies. Let > me ask him though and see if there's a good way to tidy up. You seem to be assuming a RMID is for the entire task lifetime. Since its a very limited resource that seems like a weird assumption to me; there's plenty scenarios in which you'd want to re-use RMIDs that belong to a still running context. At which point you need to force wipe.. otherwise its impossible to tell when the number reported makes any kind of sense. _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
