On Tue, 16 Sep 2014 08:44:03 +0200 Ingo Molnar <mi...@kernel.org> wrote:
> > * Chuck Ebbert <cebbert.l...@gmail.com> wrote: > > > On Tue, 16 Sep 2014 05:29:20 +0200 > > Peter Zijlstra <pet...@infradead.org> wrote: > > > > > On Mon, Sep 15, 2014 at 03:26:41PM -0700, Dave Hansen wrote: > > > > > > > > I'm getting the spew below when booting with Haswell (Xeon > > > > E5-2699) CPUs and the "Cluster-on-Die" (CoD) feature > > > > enabled in the BIOS. > > > > > > What is that cluster-on-die thing? I've heard it before but > > > never could find anything on it. > > > > Each CPU has 2.5MB of L3 connected together in a ring that > > makes it all act like a single shared cache. The HW tries to > > place the data so it's closest to the CPU that uses it. On the > > larger processors there are two rings with an interconnect > > between them that adds latency if a cache fetch has to cross > > that. CoD breaks that connection and effectively gives you two > > nodes on one die. > > Note that that's not really a 'NUMA node' in the way lots of > places in the kernel assume it: permanent placement assymetry > (and access cost assymetry) of RAM. > > It's a new topology construct that needs new handling (and > probably a new mask): Non Uniform Cache Architecture (NUCA) > or so. Hmm, looking closer at the diagram, each ring has its own memory controller, so it really is NUMA if you break the interconnect between that caches. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
