Messages in this thread | | | Date | Wed, 10 Jul 2013 13:09:26 +1000 | From | Michael Ellerman <> | Subject | Re: [PATCH v2 2/2] perf tools: Make Power7 events available for perf |
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On Tue, Jul 09, 2013 at 10:14:34AM +0200, Peter Zijlstra wrote: > On Mon, Jul 08, 2013 at 10:24:34PM -0400, Vince Weaver wrote: > > > > So something like they have on ARM? > > > > vince@pandaboard:/sys/bus/event_source/devices$ ls -l > > lrwxrwxrwx 1 root root 0 Jul 8 21:57 ARMv7 Cortex-A9 -> ../../../devices/ARMv7 Cortex-A9 > > lrwxrwxrwx 1 root root 0 Jul 8 21:57 breakpoint -> ../../../devices/breakpoint > > lrwxrwxrwx 1 root root 0 Jul 8 21:57 software -> ../../../devices/software > > lrwxrwxrwx 1 root root 0 Jul 8 21:57 tracepoint -> ../../../devices/tracepoint > > Right so what I remember of the ARM case is that their /proc/cpuinfo isn't > sufficient to identify their PMU. And they don't have a cpuid like instruction > at all. > > > > For the cpu you can obviously just detect what processor you're on with > > > cpuid or whatever, but it's a bit of a hack. And that really doesn't > > > work for non-cpu PMUs. > > > > why is it a hack to use cpuid? > > I agree, for x86 cpuid is perfectly fine, as would /proc/cpuinfo be, I suspect > that just the model number is sufficient in most cases, even for uncore stuff.
What about things on PCI? Other strange buses?
As long as everything's in /sys then it should be _possible_ for userspace to work out what's what, but it's going to end up with a bunch of detection logic and heuristics in the library.
At which point you've just rewritten libpfm4.
cheers
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