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

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Date:   Fri, 11 Sep 2020 12:37:48 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Kan Liang <kan.liang@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH V2 3/4] perf stat: Support new per thread TopDown metrics

Hello,

On Thu, Sep 10, 2020 at 10:48 PM <kan.liang@...ux.intel.com> wrote:
>
> From: Andi Kleen <ak@...ux.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@...hat.com>
> Co-developed-by: Kan Liang <kan.liang@...ux.intel.com>
> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
> Signed-off-by: Andi Kleen <ak@...ux.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) ?

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,