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authorBorislav Petkov <bp@suse.de>2017-02-07 03:40:05 +0300
committerArnaldo Carvalho de Melo <acme@redhat.com>2017-03-04 01:07:13 +0300
commit02d492e5dcb72c004d213756eb87c9d62a6d76a7 (patch)
tree726e562baa9e9d3bb12580814e874fcfb02748b5
parent771ceddaadd0a2b31603034b36dca50943ff6836 (diff)
downloadlinux-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.c11
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)