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Message-ID: <CAP-5=fUJFFOQzbPyef0F0UixFFD4Mtfh2iYc6aMXsT0mr_DXqA@mail.gmail.com>
Date: Mon, 17 Nov 2025 20:36:34 -0800
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
"Dr. David Alan Gilbert" <linux@...blig.org>, Yang Li <yang.lee@...ux.alibaba.com>,
James Clark <james.clark@...aro.org>, Thomas Falcon <thomas.falcon@...el.com>,
Thomas Richter <tmricht@...ux.ibm.com>, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: Re: [PATCH v4 04/10] perf stat-shadow: Read tool events directly
On Mon, Nov 17, 2025 at 6:30 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> On Thu, Nov 13, 2025 at 10:05:10AM -0800, Ian Rogers wrote:
> > When reading time values for metrics don't use the globals updated in
> > builtin-stat, just read the events as regular events. The only
> > exception is for time events where nanoseconds need converting to
> > seconds as metrics assume time metrics are in seconds.
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> > tools/perf/util/stat-shadow.c | 149 +++++++++++++++-------------------
> > 1 file changed, 66 insertions(+), 83 deletions(-)
> >
> > diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
> > index b3b482e1808f..6c1ad78604e1 100644
> > --- a/tools/perf/util/stat-shadow.c
> > +++ b/tools/perf/util/stat-shadow.c
> > @@ -26,7 +26,32 @@ void perf_stat__reset_shadow_stats(void)
> > memset(&ru_stats, 0, sizeof(ru_stats));
> > }
> >
> > -static int prepare_metric(const struct metric_expr *mexp,
> > +static bool tool_pmu__is_time_event(const struct perf_stat_config *config,
> > + const struct evsel *evsel, int *tool_aggr_idx)
> > +{
> > + enum tool_pmu_event event = evsel__tool_event(evsel);
> > + int aggr_idx;
> > +
> > + if (event != TOOL_PMU__EVENT_DURATION_TIME &&
> > + event != TOOL_PMU__EVENT_USER_TIME &&
> > + event != TOOL_PMU__EVENT_SYSTEM_TIME)
> > + return false;
> > +
> > + if (config) {
> > + cpu_aggr_map__for_each_idx(aggr_idx, config->aggr_map) {
> > + if (config->aggr_map->map[aggr_idx].cpu.cpu == 0) {
> > + *tool_aggr_idx = aggr_idx;
> > + return true;
> > + }
> > + }
> > + pr_debug("Unexpected CPU0 missing in aggregation for tool event.\n");
> > + }
> > + *tool_aggr_idx = 0; /* Assume the first aggregation index works. */
> > + return true;
> > +}
> > +
> > +static int prepare_metric(struct perf_stat_config *config,
> > + const struct metric_expr *mexp,
> > const struct evsel *evsel,
> > struct expr_parse_ctx *pctx,
> > int aggr_idx)
> > @@ -36,93 +61,51 @@ static int prepare_metric(const struct metric_expr *mexp,
> > int i;
> >
> > for (i = 0; metric_events[i]; i++) {
> > + int source_count = 0, tool_aggr_idx;
> > + bool is_tool_time =
> > + tool_pmu__is_time_event(config, metric_events[i], &tool_aggr_idx);
> > + struct perf_stat_evsel *ps = metric_events[i]->stats;
> > + struct perf_stat_aggr *aggr;
> > char *n;
> > double val;
> > - int source_count = 0;
> >
> > - if (evsel__is_tool(metric_events[i])) {
> > - struct stats *stats;
> > - double scale;
> > -
> > - switch (evsel__tool_event(metric_events[i])) {
> > - case TOOL_PMU__EVENT_DURATION_TIME:
> > - stats = &walltime_nsecs_stats;
> > - scale = 1e-9;
> > - break;
> > - case TOOL_PMU__EVENT_USER_TIME:
> > - stats = &ru_stats.ru_utime_usec_stat;
> > - scale = 1e-6;
> > + /*
> > + * If there are multiple uncore PMUs and we're not reading the
> > + * leader's stats, determine the stats for the appropriate
> > + * uncore PMU.
> > + */
> > + if (evsel && evsel->metric_leader &&
> > + evsel->pmu != evsel->metric_leader->pmu &&
> > + mexp->metric_events[i]->pmu == evsel->metric_leader->pmu) {
> > + struct evsel *pos;
> > +
> > + evlist__for_each_entry(evsel->evlist, pos) {
> > + if (pos->pmu != evsel->pmu)
> > + continue;
> > + if (pos->metric_leader != mexp->metric_events[i])
> > + continue;
> > + ps = pos->stats;
> > + source_count = 1;
> > break;
> > - case TOOL_PMU__EVENT_SYSTEM_TIME:
> > - stats = &ru_stats.ru_stime_usec_stat;
> > - scale = 1e-6;
> > - break;
>
> I think this was broken as it seems to be converted to nsec in the
> update_rusage_stats().
The global utime/stime is in usecs as in the name. In the tool_pmu it
is converted to nanoseconds, for consistency with duration_time. In
the new code the counters are all in nanoseconds and so the same
scaling factor can be applied.
> > - case TOOL_PMU__EVENT_NONE:
> > - pr_err("Invalid tool event 'none'");
> > - abort();
> > - case TOOL_PMU__EVENT_MAX:
> > - pr_err("Invalid tool event 'max'");
> > - abort();
> > - case TOOL_PMU__EVENT_HAS_PMEM:
> > - case TOOL_PMU__EVENT_NUM_CORES:
> > - case TOOL_PMU__EVENT_NUM_CPUS:
> > - case TOOL_PMU__EVENT_NUM_CPUS_ONLINE:
> > - case TOOL_PMU__EVENT_NUM_DIES:
> > - case TOOL_PMU__EVENT_NUM_PACKAGES:
> > - case TOOL_PMU__EVENT_SLOTS:
> > - case TOOL_PMU__EVENT_SMT_ON:
> > - case TOOL_PMU__EVENT_SYSTEM_TSC_FREQ:
> > - case TOOL_PMU__EVENT_CORE_WIDE:
> > - case TOOL_PMU__EVENT_TARGET_CPU:
> > - default:
> > - pr_err("Unexpected tool event '%s'", evsel__name(metric_events[i]));
> > - abort();
> > }
> > - val = avg_stats(stats) * scale;
> > - source_count = 1;
> > - } else {
> > - struct perf_stat_evsel *ps = metric_events[i]->stats;
> > - struct perf_stat_aggr *aggr;
> > -
> > + }
> > + /* Time events are always on CPU0, the first aggregation index. */
> > + aggr = &ps->aggr[is_tool_time ? tool_aggr_idx : aggr_idx];
> > + if (!aggr || !metric_events[i]->supported) {
> > /*
> > - * If there are multiple uncore PMUs and we're not
> > - * reading the leader's stats, determine the stats for
> > - * the appropriate uncore PMU.
> > + * Not supported events will have a count of 0, which
> > + * can be confusing in a metric. Explicitly set the
> > + * value to NAN. Not counted events (enable time of 0)
> > + * are read as 0.
> > */
> > - if (evsel && evsel->metric_leader &&
> > - evsel->pmu != evsel->metric_leader->pmu &&
> > - mexp->metric_events[i]->pmu == evsel->metric_leader->pmu) {
> > - struct evsel *pos;
> > -
> > - evlist__for_each_entry(evsel->evlist, pos) {
> > - if (pos->pmu != evsel->pmu)
> > - continue;
> > - if (pos->metric_leader != mexp->metric_events[i])
> > - continue;
> > - ps = pos->stats;
> > - source_count = 1;
> > - break;
> > - }
> > - }
> > - aggr = &ps->aggr[aggr_idx];
> > - if (!aggr)
> > - break;
> > -
> > - if (!metric_events[i]->supported) {
> > - /*
> > - * Not supported events will have a count of 0,
> > - * which can be confusing in a
> > - * metric. Explicitly set the value to NAN. Not
> > - * counted events (enable time of 0) are read as
> > - * 0.
> > - */
> > - val = NAN;
> > - source_count = 0;
> > - } else {
> > - val = aggr->counts.val;
> > - if (!source_count)
> > - source_count = evsel__source_count(metric_events[i]);
> > - }
> > + val = NAN;
> > + source_count = 0;
> > + } else {
> > + val = aggr->counts.val;
> > + if (is_tool_time)
> > + val *= 1e-9; /* Convert time event nanoseconds to seconds. */
>
> And this code treats all time events are in nsec now.
That's correct: user_time, system_time and duration_time are all
counters that give a count in nanoseconds. However, in the metrics, I
guess as the counts are doubles, the time has always been in whole
seconds.
Thanks,
Ian
> Thanks,
> Namhyung
>
>
> > + if (!source_count)
> > + source_count = evsel__source_count(metric_events[i]);
> > }
> > n = strdup(evsel__metric_id(metric_events[i]));
> > if (!n)
> > @@ -168,7 +151,7 @@ static void generic_metric(struct perf_stat_config *config,
> > pctx->sctx.user_requested_cpu_list = strdup(config->user_requested_cpu_list);
> > pctx->sctx.runtime = runtime;
> > pctx->sctx.system_wide = config->system_wide;
> > - i = prepare_metric(mexp, evsel, pctx, aggr_idx);
> > + i = prepare_metric(config, mexp, evsel, pctx, aggr_idx);
> > if (i < 0) {
> > expr__ctx_free(pctx);
> > return;
> > @@ -229,7 +212,7 @@ double test_generic_metric(struct metric_expr *mexp, int aggr_idx)
> > if (!pctx)
> > return NAN;
> >
> > - if (prepare_metric(mexp, /*evsel=*/NULL, pctx, aggr_idx) < 0)
> > + if (prepare_metric(/*config=*/NULL, mexp, /*evsel=*/NULL, pctx, aggr_idx) < 0)
> > goto out;
> >
> > if (expr__parse(&ratio, pctx, mexp->metric_expr))
> > --
> > 2.51.2.1041.gc1ab5b90ca-goog
> >
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