Em Fri, May 26, 2017 at 02:31:40PM +0200, Jiri Olsa escreveu: > The switch tracking test keeps failing on P4 cpu, > when NMI watchdog is enabled. > > The reason is that P4 pmu uses substitute event for cycles > when it's already taken (in our case by NMI watchdog), but > this event does not give even results like cycles, and we > could end up with no samples at all for our short > measuring period. > > Fixing this by using "instructions:u" event instead, > which seems to be stable enough.
The original author of this test entry is Adrian, so would be nice for him to take a look and give his Ack, Adrian? - Arnaldo > Cc: Michael Petlan <[email protected]> > Link: http://lkml.kernel.org/n/[email protected] > Signed-off-by: Jiri Olsa <[email protected]> > --- > tools/perf/tests/switch-tracking.c | 27 +++++++++++++++++++++++++-- > 1 file changed, 25 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/tests/switch-tracking.c > b/tools/perf/tests/switch-tracking.c > index 65474fd80da7..e519819ea2e5 100644 > --- a/tools/perf/tests/switch-tracking.c > +++ b/tools/perf/tests/switch-tracking.c > @@ -10,6 +10,7 @@ > #include "thread_map.h" > #include "cpumap.h" > #include "tests.h" > +#include "header.h" > > static int spin_sleep(void) > { > @@ -298,6 +299,27 @@ static int process_events(struct perf_evlist *evlist, > return ret; > } > > +static const char *get_hw_counter(void) > +{ > + const char *counter = "cycles:u"; > + char *cpuid; > + > + cpuid = get_cpuid_str(); > + > + /* > + * P4 pmu uses substitute event for cycles if it's already > + * taken, but it does not give even results like cycles, > + * and we could end up with no samples at all for our short > + * measuring period. Using "instructions:u" event instead, > + * which seems to be stable enough. > + */ > + if (!strcmp("GenuineIntel-15-4", cpuid)) > + counter = "instructions:u"; > + > + pr_debug("using '%s' HW counter"); > + return counter; > +} > + > /** > * test__switch_tracking - test using sched_switch and tracking events. > * > @@ -308,6 +330,7 @@ static int process_events(struct perf_evlist *evlist, > */ > int test__switch_tracking(int subtest __maybe_unused) > { > + const char *hw_counter = get_hw_counter(); > const char *sched_switch = "sched:sched_switch"; > struct switch_tracking switch_tracking = { .tids = NULL, }; > struct record_opts opts = { > @@ -357,9 +380,9 @@ int test__switch_tracking(int subtest __maybe_unused) > cpu_clocks_evsel = perf_evlist__last(evlist); > > /* Second event */ > - err = parse_events(evlist, "cycles:u", NULL); > + err = parse_events(evlist, hw_counter, NULL); > if (err) { > - pr_debug("Failed to parse event cycles:u\n"); > + pr_debug("Failed to parse event %s\n", hw_counter); > goto out_err; > } > > -- > 2.9.4
