Re: [PATCH V2 3/4] perf stat: Support new per thread TopDown metrics

["Liang, Kan" <kan.liang@linux.intel.com>]

On 9/10/2020 11:37 PM, Namhyung Kim wrote:
> Hello,
> 
> On Thu, Sep 10, 2020 at 10:48 PM <kan.liang@linux.intel.com> wrote:
>>
>> From: Andi Kleen <ak@linux.intel.com>
>>
>> Icelake has support for reporting per thread TopDown metrics.
>> These are reported differently than the previous TopDown support,
>> each metric is standalone, but scaled to pipeline "slots".
>> We don't need to do anything special for HyperThreading anymore.
>> Teach perf stat --topdown to handle these new metrics and
>> print them in the same way as the previous TopDown metrics.
>> The restrictions of only being able to report information per core is
>> gone.
>>
>> Acked-by: Jiri Olsa <jolsa@redhat.com>
>> Co-developed-by: Kan Liang <kan.liang@linux.intel.com>
>> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
>> Signed-off-by: Andi Kleen <ak@linux.intel.com>
>> ---
>>   tools/perf/Documentation/perf-stat.txt |  7 +-
>>   tools/perf/builtin-stat.c              | 30 ++++++++-
>>   tools/perf/util/stat-shadow.c          | 89 ++++++++++++++++++++++++++
>>   tools/perf/util/stat.c                 |  4 ++
>>   tools/perf/util/stat.h                 |  8 +++
>>   5 files changed, 134 insertions(+), 4 deletions(-)
>>
>> diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
>> index c9bfefc051fb..e803dbdc88a8 100644
>> --- a/tools/perf/Documentation/perf-stat.txt
>> +++ b/tools/perf/Documentation/perf-stat.txt
>> @@ -357,6 +357,11 @@ if the workload is actually bound by the CPU and not by something else.
>>   For best results it is usually a good idea to use it with interval
>>   mode like -I 1000, as the bottleneck of workloads can change often.
>>
>> +This enables --metric-only, unless overridden with --no-metric-only.
>> +
>> +The following restrictions only apply to older Intel CPUs and Atom,
>> +on newer CPUs (IceLake and later) TopDown can be collected for any thread:
>> +
>>   The top down metrics are collected per core instead of per
>>   CPU thread. Per core mode is automatically enabled
>>   and -a (global monitoring) is needed, requiring root rights or
>> @@ -368,8 +373,6 @@ echo 0 > /proc/sys/kernel/nmi_watchdog
>>   for best results. Otherwise the bottlenecks may be inconsistent
>>   on workload with changing phases.
>>
>> -This enables --metric-only, unless overridden with --no-metric-only.
>> -
>>   To interpret the results it is usually needed to know on which
>>   CPUs the workload runs on. If needed the CPUs can be forced using
>>   taskset.
>> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
>> index 5583e22ca808..6290da5bd142 100644
>> --- a/tools/perf/builtin-stat.c
>> +++ b/tools/perf/builtin-stat.c
>> @@ -128,6 +128,15 @@ static const char * topdown_attrs[] = {
>>          NULL,
>>   };
>>
>> +static const char *topdown_metric_attrs[] = {
>> +       "slots",
>> +       "topdown-retiring",
>> +       "topdown-bad-spec",
>> +       "topdown-fe-bound",
>> +       "topdown-be-bound",
>> +       NULL,
>> +};
>> +
>>   static const char *smi_cost_attrs = {
>>          "{"
>>          "msr/aperf/,"
>> @@ -1691,6 +1700,24 @@ static int add_default_attributes(void)
>>                  char *str = NULL;
>>                  bool warn = false;
>>
>> +               if (!force_metric_only)
>> +                       stat_config.metric_only = true;
>> +
>> +               if (topdown_filter_events(topdown_metric_attrs, &str, 1) < 0) {
>> +                       pr_err("Out of memory\n");
>> +                       return -1;
>> +               }
>> +               if (topdown_metric_attrs[0] && str) {
>> +                       if (!stat_config.interval && !stat_config.metric_only) {
>> +                               fprintf(stat_config.output,
>> +                                       "Topdown accuracy may decrease when measuring long periods.\n"
>> +                                       "Please print the result regularly, e.g. -I1000\n");
>> +                       }
>> +                       goto setup_metrics;
>> +               }
>> +
>> +               str = NULL;
> 
> zfree(&str) ?

Yes, even the topdown events don't exist, str is still allocated.
The str should be free.

I will send V3 to fix it shortly.

Thanks,
Kan

> 
> Thanks
> Namhyung
> 
> 
>> +
>>                  if (stat_config.aggr_mode != AGGR_GLOBAL &&
>>                      stat_config.aggr_mode != AGGR_CORE) {
>>                          pr_err("top down event configuration requires --per-core mode\n");
>> @@ -1702,8 +1729,6 @@ static int add_default_attributes(void)
>>                          return -1;
>>                  }
>>
>> -               if (!force_metric_only)
>> -                       stat_config.metric_only = true;
>>                  if (topdown_filter_events(topdown_attrs, &str,
>>                                  arch_topdown_check_group(&warn)) < 0) {
>>                          pr_err("Out of memory\n");
>> @@ -1712,6 +1737,7 @@ static int add_default_attributes(void)
>>                  if (topdown_attrs[0] && str) {
>>                          if (warn)
>>                                  arch_topdown_group_warn();
>> +setup_metrics:
>>                          err = parse_events(evsel_list, str, &errinfo);
>>                          if (err) {
>>                                  fprintf(stderr,