perf stat: Support new per thread TopDown metrics

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.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Co-developed-by: Kan Liang <kan.liang@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20200911144808.27603-4-kan.liang@linux.intel.com
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 7d18694e592af26a29fdeabf032deb7a17b1091d..5bf3d7ae466008d2027287b0fabcc880a21e5dc3 100644 (file)
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -363,6 +363,11 @@ 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
@@ -374,8 +379,6 @@ 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 a39bb28b44f93484f8d83cda3b946e5a0fccc031..17fbbd03e15484e434a39eb3cf1c9b03af2e08a7 100644 (file)
--- 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/,"
@@ -1677,6 +1686,24 @@ 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;
+               }
+
+               zfree(&str);
+
                if (stat_config.aggr_mode != AGGR_GLOBAL &&
                    stat_config.aggr_mode != AGGR_CORE) {
                        pr_err("top down event configuration requires --per-core mode\n");
@@ -1688,8 +1715,6 @@ 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");
@@ -1698,6 +1723,7 @@ 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,

diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
index 924b54d15d5406b98d1236b57a8db0b90d46545d..901265127e3698126bc9f395058ee4f12fd05419 100644 (file)
--- a/tools/perf/util/stat-shadow.c
+++ b/tools/perf/util/stat-shadow.c
@@ -241,6 +241,18 @@ void perf_stat__update_shadow_stats(struct evsel *counter, u64 count,
        else if (perf_stat_evsel__is(counter, TOPDOWN_RECOVERY_BUBBLES))
                update_runtime_stat(st, STAT_TOPDOWN_RECOVERY_BUBBLES,
                                    ctx, cpu, count);
+       else if (perf_stat_evsel__is(counter, TOPDOWN_RETIRING))
+               update_runtime_stat(st, STAT_TOPDOWN_RETIRING,
+                                   ctx, cpu, count);
+       else if (perf_stat_evsel__is(counter, TOPDOWN_BAD_SPEC))
+               update_runtime_stat(st, STAT_TOPDOWN_BAD_SPEC,
+                                   ctx, cpu, count);
+       else if (perf_stat_evsel__is(counter, TOPDOWN_FE_BOUND))
+               update_runtime_stat(st, STAT_TOPDOWN_FE_BOUND,
+                                   ctx, cpu, count);
+       else if (perf_stat_evsel__is(counter, TOPDOWN_BE_BOUND))
+               update_runtime_stat(st, STAT_TOPDOWN_BE_BOUND,
+                                   ctx, cpu, count);
        else if (evsel__match(counter, HARDWARE, HW_STALLED_CYCLES_FRONTEND))
                update_runtime_stat(st, STAT_STALLED_CYCLES_FRONT,
                                    ctx, cpu, count);
@@ -705,6 +717,47 @@ static double td_be_bound(int ctx, int cpu, struct runtime_stat *st)
        return sanitize_val(1.0 - sum);
 }
 
+/*
+ * Kernel reports metrics multiplied with slots. To get back
+ * the ratios we need to recreate the sum.
+ */
+
+static double td_metric_ratio(int ctx, int cpu,
+                             enum stat_type type,
+                             struct runtime_stat *stat)
+{
+       double sum = runtime_stat_avg(stat, STAT_TOPDOWN_RETIRING, ctx, cpu) +
+               runtime_stat_avg(stat, STAT_TOPDOWN_FE_BOUND, ctx, cpu) +
+               runtime_stat_avg(stat, STAT_TOPDOWN_BE_BOUND, ctx, cpu) +
+               runtime_stat_avg(stat, STAT_TOPDOWN_BAD_SPEC, ctx, cpu);
+       double d = runtime_stat_avg(stat, type, ctx, cpu);
+
+       if (sum)
+               return d / sum;
+       return 0;
+}
+
+/*
+ * ... but only if most of the values are actually available.
+ * We allow two missing.
+ */
+
+static bool full_td(int ctx, int cpu,
+                   struct runtime_stat *stat)
+{
+       int c = 0;
+
+       if (runtime_stat_avg(stat, STAT_TOPDOWN_RETIRING, ctx, cpu) > 0)
+               c++;
+       if (runtime_stat_avg(stat, STAT_TOPDOWN_BE_BOUND, ctx, cpu) > 0)
+               c++;
+       if (runtime_stat_avg(stat, STAT_TOPDOWN_FE_BOUND, ctx, cpu) > 0)
+               c++;
+       if (runtime_stat_avg(stat, STAT_TOPDOWN_BAD_SPEC, ctx, cpu) > 0)
+               c++;
+       return c >= 2;
+}
+
 static void print_smi_cost(struct perf_stat_config *config,
                           int cpu, struct evsel *evsel,
                           struct perf_stat_output_ctx *out,
@@ -1073,6 +1126,42 @@ void perf_stat__print_shadow_stats(struct perf_stat_config *config,
                                        be_bound * 100.);
                else
                        print_metric(config, ctxp, NULL, NULL, name, 0);
+       } else if (perf_stat_evsel__is(evsel, TOPDOWN_RETIRING) &&
+                       full_td(ctx, cpu, st)) {
+               double retiring = td_metric_ratio(ctx, cpu,
+                                                 STAT_TOPDOWN_RETIRING, st);
+
+               if (retiring > 0.7)
+                       color = PERF_COLOR_GREEN;
+               print_metric(config, ctxp, color, "%8.1f%%", "retiring",
+                               retiring * 100.);
+       } else if (perf_stat_evsel__is(evsel, TOPDOWN_FE_BOUND) &&
+                       full_td(ctx, cpu, st)) {
+               double fe_bound = td_metric_ratio(ctx, cpu,
+                                                 STAT_TOPDOWN_FE_BOUND, st);
+
+               if (fe_bound > 0.2)
+                       color = PERF_COLOR_RED;
+               print_metric(config, ctxp, color, "%8.1f%%", "frontend bound",
+                               fe_bound * 100.);
+       } else if (perf_stat_evsel__is(evsel, TOPDOWN_BE_BOUND) &&
+                       full_td(ctx, cpu, st)) {
+               double be_bound = td_metric_ratio(ctx, cpu,
+                                                 STAT_TOPDOWN_BE_BOUND, st);
+
+               if (be_bound > 0.2)
+                       color = PERF_COLOR_RED;
+               print_metric(config, ctxp, color, "%8.1f%%", "backend bound",
+                               be_bound * 100.);
+       } else if (perf_stat_evsel__is(evsel, TOPDOWN_BAD_SPEC) &&
+                       full_td(ctx, cpu, st)) {
+               double bad_spec = td_metric_ratio(ctx, cpu,
+                                                 STAT_TOPDOWN_BAD_SPEC, st);
+
+               if (bad_spec > 0.1)
+                       color = PERF_COLOR_RED;
+               print_metric(config, ctxp, color, "%8.1f%%", "bad speculation",
+                               bad_spec * 100.);
        } else if (evsel->metric_expr) {
                generic_metric(config, evsel->metric_expr, evsel->metric_events, NULL,
                                evsel->name, evsel->metric_name, NULL, 1, cpu, out, st);

diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
index cdb154381a87361de6a229c040217b350314c28d..bd0decd6d7535ed1c034863df738ac4f48904512 100644 (file)
--- a/tools/perf/util/stat.c
+++ b/tools/perf/util/stat.c
@@ -95,6 +95,10 @@ static const char *id_str[PERF_STAT_EVSEL_ID__MAX] = {
        ID(TOPDOWN_SLOTS_RETIRED, topdown-slots-retired),
        ID(TOPDOWN_FETCH_BUBBLES, topdown-fetch-bubbles),
        ID(TOPDOWN_RECOVERY_BUBBLES, topdown-recovery-bubbles),
+       ID(TOPDOWN_RETIRING, topdown-retiring),
+       ID(TOPDOWN_BAD_SPEC, topdown-bad-spec),
+       ID(TOPDOWN_FE_BOUND, topdown-fe-bound),
+       ID(TOPDOWN_BE_BOUND, topdown-be-bound),
        ID(SMI_NUM, msr/smi/),
        ID(APERF, msr/aperf/),
 };

diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h
index 9911fc6adbfdd7e843be3212f051cc984545b790..f36c8c92efa0cd1d9359b25be3167c5bd33ebdeb 100644 (file)
--- a/tools/perf/util/stat.h
+++ b/tools/perf/util/stat.h
@@ -28,6 +28,10 @@ enum perf_stat_evsel_id {
        PERF_STAT_EVSEL_ID__TOPDOWN_SLOTS_RETIRED,
        PERF_STAT_EVSEL_ID__TOPDOWN_FETCH_BUBBLES,
        PERF_STAT_EVSEL_ID__TOPDOWN_RECOVERY_BUBBLES,
+       PERF_STAT_EVSEL_ID__TOPDOWN_RETIRING,
+       PERF_STAT_EVSEL_ID__TOPDOWN_BAD_SPEC,
+       PERF_STAT_EVSEL_ID__TOPDOWN_FE_BOUND,
+       PERF_STAT_EVSEL_ID__TOPDOWN_BE_BOUND,
        PERF_STAT_EVSEL_ID__SMI_NUM,
        PERF_STAT_EVSEL_ID__APERF,
        PERF_STAT_EVSEL_ID__MAX,
@@ -82,6 +86,10 @@ enum stat_type {
        STAT_TOPDOWN_SLOTS_RETIRED,
        STAT_TOPDOWN_FETCH_BUBBLES,
        STAT_TOPDOWN_RECOVERY_BUBBLES,
+       STAT_TOPDOWN_RETIRING,
+       STAT_TOPDOWN_BAD_SPEC,
+       STAT_TOPDOWN_FE_BOUND,
+       STAT_TOPDOWN_BE_BOUND,
        STAT_SMI_NUM,
        STAT_APERF,
        STAT_MAX