Re: [RFC PATCH 3/3 v3] perf: Update perf tool to monitor uncore events

Martin Hicks
2010-12-15T17:14:55Z

On Tue, Dec 14, 2010 at 03:13:14PM +0100, Andi Kleen wrote:
> On Tue, Dec 14, 2010 at 01:33:27PM +0100, Peter Zijlstra wrote:
> > > > First of all, "uncore" is an x86-specific term and so it's not clear to
> > > > me if you meant for all arches to utilize this encoding for all "not
> > > > core but on the same die" events (IBM Power arch refers to this as
> > > > "nest" logic).
> >
> > I don't think the x86 uncore matches the "not on core but on the same
> > die" definition. The x86-uncore thing is more like a memory controller
> > PMU (and since the memory controller is on die it is of course on die,
>
> memory controller + interconnect + cache + power management + various other things.
>
> Older x86 CPUs also had special PMUs on die for parts of that, but
> without memory controller.
>
> > but its not just any random on-die thing).
> >
> > The wire-speed thing has tons of special purpose 'cores' on die, each of
> > them having a PMU.
>
> Modern x86 CPUs also have other PMUs, at least in package (e.g. in the
> GPU)
>
> > Using the sysfs stuff you could actually expose each individually.
>
> I expect this will be also needed on x86. Also there are x86 SOCs
> where other parts of the SOC will have their own counters too.
> So in general a flexible scheme to describe that is useful.

Definitely. For instance, SGI intends to use this to expose the
performance metrics that are found in the ASIC hub chip that does the
cache coherency in the big SSI systems. There will be one of these per
blade.

mh