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author | Borislav Petkov <bp@suse.de> | 2017-02-07 03:40:05 +0300 |
---|---|---|
committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2017-03-04 01:07:13 +0300 |
commit | 02d492e5dcb72c004d213756eb87c9d62a6d76a7 (patch) | |
tree | 726e562baa9e9d3bb12580814e874fcfb02748b5 | |
parent | 771ceddaadd0a2b31603034b36dca50943ff6836 (diff) | |
download | linux-02d492e5dcb72c004d213756eb87c9d62a6d76a7.tar.xz |
perf stat: Issue a HW watchdog disable hint
When using perf stat on an AMD F15h system with the default hw events
attributes, some of the events don't get counted:
Performance counter stats for 'sleep 1':
0.749208 task-clock (msec) # 0.001 CPUs utilized
1 context-switches # 0.001 M/sec
0 cpu-migrations # 0.000 K/sec
54 page-faults # 0.072 M/sec
1,122,815 cycles # 1.499 GHz
286,740 stalled-cycles-frontend # 25.54% frontend cycles idle
<not counted> stalled-cycles-backend (0.00%)
^^^^^^^^^^^^
<not counted> instructions (0.00%)
^^^^^^^^^^^^
<not counted> branches (0.00%)
<not counted> branch-misses (0.00%)
1.001550070 seconds time elapsed
The reason is that we have the HW watchdog consuming one PMU counter and
when perf tries to schedule 6 events on 6 counters and some of those
counters are constrained to only a specific subset of PMCs by the
hardware, the event scheduling fails.
So issue a hint to disable the HW watchdog around a perf stat session.
Committer note:
Testing it...
# perf stat -d usleep 1
Performance counter stats for 'usleep 1':
1.180203 task-clock (msec) # 0.490 CPUs utilized
1 context-switches # 0.847 K/sec
0 cpu-migrations # 0.000 K/sec
54 page-faults # 0.046 M/sec
184,754 cycles # 0.157 GHz
714,553 instructions # 3.87 insn per cycle
154,661 branches # 131.046 M/sec
7,247 branch-misses # 4.69% of all branches
219,984 L1-dcache-loads # 186.395 M/sec
17,600 L1-dcache-load-misses # 8.00% of all L1-dcache hits (90.16%)
<not counted> LLC-loads (0.00%)
<not counted> LLC-load-misses (0.00%)
0.002406823 seconds time elapsed
Some events weren't counted. Try disabling the NMI watchdog:
echo 0 > /proc/sys/kernel/nmi_watchdog
perf stat ...
echo 1 > /proc/sys/kernel/nmi_watchdog
#
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Richter <rric@kernel.org>
Cc: Vince Weaver <vince@deater.net>
Link: http://lkml.kernel.org/r/20170211183218.ijnvb5f7ciyuunx4@pd.tnic
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
-rw-r--r-- | tools/perf/builtin-stat.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index 13b54999ad79..f4f555a67e9b 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -146,6 +146,7 @@ static aggr_get_id_t aggr_get_id; static bool append_file; static const char *output_name; static int output_fd; +static int print_free_counters_hint; struct perf_stat { bool record; @@ -1109,6 +1110,9 @@ static void printout(int id, int nr, struct perf_evsel *counter, double uval, counter->supported ? CNTR_NOT_COUNTED : CNTR_NOT_SUPPORTED, csv_sep); + if (counter->supported) + print_free_counters_hint = 1; + fprintf(stat_config.output, "%-*s%s", csv_output ? 0 : unit_width, counter->unit, csv_sep); @@ -1477,6 +1481,13 @@ static void print_footer(void) avg_stats(&walltime_nsecs_stats)); } fprintf(output, "\n\n"); + + if (print_free_counters_hint) + fprintf(output, +"Some events weren't counted. Try disabling the NMI watchdog:\n" +" echo 0 > /proc/sys/kernel/nmi_watchdog\n" +" perf stat ...\n" +" echo 1 > /proc/sys/kernel/nmi_watchdog\n"); } static void print_counters(struct timespec *ts, int argc, const char **argv) |