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Consider: ``` $ perf stat -e cycles,data_read,instructions true Performance counter stats for 'true': 357,457 cycles:u MiB data_read:u 156,182 instructions:u # 0.44 insn pe= r cycle 0.001250315 seconds time elapsed 0.001283000 seconds user 0.000000000 seconds sys ``` To understand why the data_read uncore event failed, with this change: ``` $ perf stat -v -e cycles,data_read,instructions true Using CPUID GenuineIntel-6-8D-1 cycles -> cpu/cycles/ data_read -> uncore_imc_free_running_0/data_read/ data_read -> uncore_imc_free_running_1/data_read/ instructions -> cpu/instructions/ Control descriptor is not initialized Warning: kernel.perf_event_paranoid=3D2, trying to fall back to excluding kernel and= hypervisor samples Warning: kernel.perf_event_paranoid=3D2, trying to fall back to excluding kernel and= hypervisor samples Warning: kernel.perf_event_paranoid=3D2, trying to fall back to excluding kernel and= hypervisor samples Warning: data_read:u event is not supported by the kernel. Invalid event (data_read:u) in per-thread mode, enable system wide with '-a= '. Warning: kernel.perf_event_paranoid=3D2, trying to fall back to excluding kernel and= hypervisor samples Warning: data_read:u event is not supported by the kernel. Invalid event (data_read:u) in per-thread mode, enable system wide with '-a= '. cycles:u: 351621 362833 362833 failed to read counter data_read:u failed to read counter data_read:u instructions:u: 156184 362833 362833 Performance counter stats for 'true': 351,621 cycles:u MiB data_read:u 156,184 instructions:u # 0.44 insn pe= r cycle 0.001584472 seconds time elapsed 0.001811000 seconds user 0.000000000 seconds sys ``` where without this change only "data_read:u event is not supported by the kernel." is shown. Signed-off-by: Ian Rogers --- tools/perf/builtin-stat.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index 7006f848f87a..84e06ec09cc2 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -624,8 +624,9 @@ static enum counter_recovery stat_handle_error(struct e= vsel *counter, int err) */ if (err =3D=3D EINVAL || err =3D=3D ENOSYS || err =3D=3D ENOENT || err = =3D=3D ENXIO) { if (verbose > 0) { - ui__warning("%s event is not supported by the kernel.\n", - evsel__name(counter)); + evsel__open_strerror(counter, &target, err, msg, sizeof(msg)); + ui__warning("%s event is not supported by the kernel.\n%s\n", + evsel__name(counter), msg); } return COUNTER_SKIP; } @@ -649,10 +650,11 @@ static enum counter_recovery stat_handle_error(struct= evsel *counter, int err) } } if (verbose > 0) { + evsel__open_strerror(counter, &target, err, msg, sizeof(msg)); ui__warning(err =3D=3D EOPNOTSUPP - ? "%s event is not supported by the kernel.\n" - : "skipping event %s that kernel failed to open.\n", - evsel__name(counter)); + ? "%s event is not supported by the kernel.\n%s\n" + : "skipping event %s that kernel failed to open.\n%s\n", + evsel__name(counter), msg); } return COUNTER_SKIP; } --=20 2.51.0.618.g983fd99d29-goog