From: Borislav Petkov bp@suse.de
[ Upstream commit 02d492e5dcb72c004d213756eb87c9d62a6d76a7 ]
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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- tools/perf/builtin-stat.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index 688dea7cb08f..c241167c76c9 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)