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Message-ID: <20201105224121.GA4112111@krava>
Date: Thu, 5 Nov 2020 23:41:21 +0100
From: Jiri Olsa <jolsa@...hat.com>
To: Rob Herring <robh@...nel.org>
Cc: Will Deacon <will@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Namhyung Kim <namhyung@...nel.org>,
Raphael Gault <raphael.gault@....com>,
Mark Rutland <mark.rutland@....com>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Ian Rogers <irogers@...gle.com>,
Honnappa Nagarahalli <honnappa.nagarahalli@....com>,
Itaru Kitayama <itaru.kitayama@...il.com>
Subject: Re: [PATCH v4 4/9] libperf: Add libperf_evsel__mmap()
On Thu, Nov 05, 2020 at 10:19:24AM -0600, Rob Herring wrote:
SNIP
> > > >
> > > > that maps page for each event, then perf_evsel__read
> > > > could go through the fast code, no?
> > >
> > > No, because we're not self-monitoring (pid == 0 and cpu == -1). With
> > > the following change:
> > >
> > > diff --git a/tools/lib/perf/tests/test-evsel.c
> > > b/tools/lib/perf/tests/test-evsel.c
> > > index eeca8203d73d..1fca9c121f7c 100644
> > > --- a/tools/lib/perf/tests/test-evsel.c
> > > +++ b/tools/lib/perf/tests/test-evsel.c
> > > @@ -17,6 +17,7 @@ static int test_stat_cpu(void)
> > > {
> > > struct perf_cpu_map *cpus;
> > > struct perf_evsel *evsel;
> > > + struct perf_event_mmap_page *pc;
> > > struct perf_event_attr attr = {
> > > .type = PERF_TYPE_SOFTWARE,
> > > .config = PERF_COUNT_SW_CPU_CLOCK,
> > > @@ -32,6 +33,15 @@ static int test_stat_cpu(void)
> > > err = perf_evsel__open(evsel, cpus, NULL);
> > > __T("failed to open evsel", err == 0);
> > >
> > > + pc = perf_evsel__mmap(evsel, 0);
> > > + __T("failed to mmap evsel", pc);
> > > +
> > > +#if defined(__i386__) || defined(__x86_64__) || defined(__aarch64__)
> > > + __T("userspace counter access not supported", pc->cap_user_rdpmc);
> > > + __T("userspace counter access not enabled", pc->index);
> > > + __T("userspace counter width not set", pc->pmc_width >= 32);
> > > +#endif
> >
> > I'll need to check, I'm surprised this would depend on the way
> > you open the event
>
> Any more thoughts on this?
sry I got stuck with other stuff.. I tried your change
and pc->cap_user_rdpmc is 0 because the test creates
software event, which does not support that
when I change that to:
.type = PERF_TYPE_HARDWARE,
.config = PERF_COUNT_HW_CPU_CYCLES,
I don't see any of those warning you added
jirka
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