This is a note to let you know that I've just added the patch titled
perf stat: Issue a HW watchdog disable hint
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-stat-issue-a-hw-watchdog-disable-hint.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Sun Mar 18 16:55:33 CET 2018
From: Borislav Petkov <bp@xxxxxxx>
Date: Tue, 7 Feb 2017 01:40:05 +0100
Subject: perf stat: Issue a HW watchdog disable hint
From: Borislav Petkov <bp@xxxxxxx>
[ 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@xxxxxxx>
Acked-by: Ingo Molnar <mingo@xxxxxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Robert Richter <rric@xxxxxxxxxx>
Cc: Vince Weaver <vince@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170211183218.ijnvb5f7ciyuunx4@xxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
tools/perf/builtin-stat.c | 11 +++++++++++
1 file changed, 11 insertions(+)
--- 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, str
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)
Patches currently in stable-queue which might be from bp@xxxxxxx are
queue-4.9/x86-mce-handle-broadcasted-mce-gracefully-with-kexec.patch
queue-4.9/perf-stat-issue-a-hw-watchdog-disable-hint.patch
queue-4.9/x86-mm-make-mmap-map_32bit-work-correctly.patch
queue-4.9/edac-altera-fix-peripheral-warnings-for-cyclone5.patch
queue-4.9/kvm-svm-setup-mcg_cap-on-amd-properly.patch
queue-4.9/x86-mce-init-some-cpu-features-early.patch