On Wed, 22 Jul, at 03:24:44PM, Jiri Olsa wrote:
> On Wed, Jul 22, 2015 at 11:38:59AM +0100, Matt Fleming wrote:
> > From: Matt Fleming <matt.flem...@intel.com>
> >
> > Peter reports that it's possible to trigger a WARN_ON_ONCE() in the
> > Intel CQM code by combining a hardware event and an Intel CQM (software)
> > event into a group. Unfortunately, the perf tools are not able to create
> > this bundle and we need to manually construct a test case.
> >
> > For posterity, record Peter's proof of concept test case in tools/perf
> > so that it presents a model for how we can perform architecture-specific
> > tests, or "arch tests", in perf in the future.
> >
> > The particular issue triggered in the test case is that when the counter
> > for the hardware event overflows and triggers a PMI we'll read both the
> > hardware event and the software event counters. Unfortunately, for CQM
> > that involves performing an IPI to read the CQM event counters on all
> > sockets, which in NMI context triggers the WARN_ON_ONCE().
> >
> > This patch is marked as RFC because I'd really like to solicit opinions
> > on this approach and hear feedback on whether this is the correct way to
> > structure these arch tests. I realise that we've already got tests for
> > the TSC, etc that are x86-specific but I didn't want to change the order
> > of the tests (say, by moving test__perf_time_to_tsc() into ARCH_TESTS)
> > in case that broke some kind of ABI.
>
> I wouldn't consider the order of tests being ABI,
> let's break it and watch ;-)
OK, that at least allows me to perform a litte more surgery on the
current tests.
> > diff --git a/tools/perf/arch/x86/include/arch-tests.h
> > b/tools/perf/arch/x86/include/arch-tests.h
> > new file mode 100644
> > index 000000000000..9d43f759e014
> > --- /dev/null
> > +++ b/tools/perf/arch/x86/include/arch-tests.h
> > @@ -0,0 +1,13 @@
> > +#ifndef ARCH_TESTS_H
> > +#define ARCH_TESTS_H
> > +
> > +/* Tests */
> > +int test__intel_cqm_count_nmi_context(void);
> > +
> > +#define ARCH_TESTS \
> > + { \
> > + .desc = "Test intel cqm nmi context read", \
> > + .func = test__intel_cqm_count_nmi_context, \
> > + },
> > +
>
> hum, I dont like much this being stuffed in macro,
> but dont have any technical reason against ;-)
>
> maybe we could add 'struct test arch_tests[]' array, that'd be
> initialized by each arch and executed in addition to the current
> 'struct test tests[]'
Makes sense to me. I'll take that approach. Thanks.
--
Matt Fleming, Intel Open Source Technology Center
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