Commit a1bf2305 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
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perf stat: Take cgroups into account for shadow stats 



As of now it doesn't consider cgroups when collecting shadow stats and
metrics so counter values from different cgroups will be saved in a same
slot.  This resulted in incorrect numbers when those cgroups have
different workloads.

For example, let's look at the scenario below: cgroups A and C runs same
workload which burns a cpu while cgroup B runs a light workload.

  $ perf stat -a -e cycles,instructions --for-each-cgroup A,B,C  sleep 1

   Performance counter stats for 'system wide':

     3,958,116,522      cycles                A
     6,722,650,929      instructions          A #    2.53  insn per cycle
         1,132,741      cycles                B
           571,743      instructions          B #    0.00  insn per cycle
     4,007,799,935      cycles                C
     6,793,181,523      instructions          C #    2.56  insn per cycle

       1.001050869 seconds time elapsed

When I run 'perf stat' with single workload, it usually shows IPC around
1.7.  We can verify it (6,722,650,929.0 / 3,958,116,522 = 1.698) for cgroup A.

But in this case, since cgroups are ignored, cycles are averaged so it
used the lower value for IPC calculation and resulted in around 2.5.

  avg cycle: (3958116522 + 1132741 + 4007799935) / 3 = 2655683066
  IPC (A)  :  6722650929 / 2655683066 = 2.531
  IPC (B)  :      571743 / 2655683066 = 0.0002
  IPC (C)  :  6793181523 / 2655683066 = 2.557

We can simply compare cgroup pointers in the evsel and it'll be NULL
when cgroups are not specified.  With this patch, I can see correct
numbers like below:

  $ perf stat -a -e cycles,instructions --for-each-cgroup A,B,C  sleep 1

  Performance counter stats for 'system wide':

     4,171,051,687      cycles                A
     7,219,793,922      instructions          A #    1.73  insn per cycle
         1,051,189      cycles                B
           583,102      instructions          B #    0.55  insn per cycle
     4,171,124,710      cycles                C
     7,192,944,580      instructions          C #    1.72  insn per cycle

       1.007909814 seconds time elapsed

Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Acked-by: default avatarJiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20210115071139.257042-2-namhyung@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 3ff1e718

tools/perf/util/stat-shadow.c

+19 −7
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
#include "evlist.h"

#include "expr.h"

#include "metricgroup.h"

#include "cgroup.h"

#include <linux/zalloc.h>



/*
@@ -28,6 +29,7 @@ struct saved_value { 
	enum stat_type type;

	int ctx;

	int cpu;

	struct cgroup *cgrp;

	struct runtime_stat *stat;

	struct stats stats;

	u64 metric_total;
@@ -57,6 +59,9 @@ static int saved_value_cmp(struct rb_node *rb_node, const void *entry) 
	if (a->ctx != b->ctx)

		return a->ctx - b->ctx;



	if (a->cgrp != b->cgrp)

		return (char *)a->cgrp < (char *)b->cgrp ? -1 : +1;



	if (a->evsel == NULL && b->evsel == NULL) {

		if (a->stat == b->stat)

			return 0;
@@ -100,7 +105,8 @@ static struct saved_value *saved_value_lookup(struct evsel *evsel, 
					      bool create,

					      enum stat_type type,

					      int ctx,

					      struct runtime_stat *st)

					      struct runtime_stat *st,

					      struct cgroup *cgrp)

{

	struct rblist *rblist;

	struct rb_node *nd;
@@ -110,6 +116,7 @@ static struct saved_value *saved_value_lookup(struct evsel *evsel, 
		.type = type,

		.ctx = ctx,

		.stat = st,

		.cgrp = cgrp,

	};



	rblist = &st->value_list;
@@ -197,6 +204,7 @@ void perf_stat__reset_shadow_per_stat(struct runtime_stat *st) 


struct runtime_stat_data {

	int ctx;

	struct cgroup *cgrp;

};



static void update_runtime_stat(struct runtime_stat *st,
@@ -205,7 +213,7 @@ static void update_runtime_stat(struct runtime_stat *st, 
				struct runtime_stat_data *rsd)

{

	struct saved_value *v = saved_value_lookup(NULL, cpu, true, type,

						   rsd->ctx, st);

						   rsd->ctx, st, rsd->cgrp);



	if (v)

		update_stats(&v->stats, count);
@@ -223,6 +231,7 @@ void perf_stat__update_shadow_stats(struct evsel *counter, u64 count, 
	struct saved_value *v;

	struct runtime_stat_data rsd = {

		.ctx = evsel_context(counter),

		.cgrp = counter->cgrp,

	};



	count *= counter->scale;
@@ -290,13 +299,14 @@ void perf_stat__update_shadow_stats(struct evsel *counter, u64 count, 
		update_runtime_stat(st, STAT_APERF, cpu, count, &rsd);



	if (counter->collect_stat) {

		v = saved_value_lookup(counter, cpu, true, STAT_NONE, 0, st);

		v = saved_value_lookup(counter, cpu, true, STAT_NONE, 0, st,

				       rsd.cgrp);

		update_stats(&v->stats, count);

		if (counter->metric_leader)

			v->metric_total += count;

	} else if (counter->metric_leader) {

		v = saved_value_lookup(counter->metric_leader,

				       cpu, true, STAT_NONE, 0, st);

				       cpu, true, STAT_NONE, 0, st, rsd.cgrp);

		v->metric_total += count;

		v->metric_other++;

	}
@@ -438,7 +448,7 @@ static double runtime_stat_avg(struct runtime_stat *st, 
{

	struct saved_value *v;



	v = saved_value_lookup(NULL, cpu, false, type, rsd->ctx, st);

	v = saved_value_lookup(NULL, cpu, false, type, rsd->ctx, st, rsd->cgrp);

	if (!v)

		return 0.0;
@@ -451,7 +461,7 @@ static double runtime_stat_n(struct runtime_stat *st, 
{

	struct saved_value *v;



	v = saved_value_lookup(NULL, cpu, false, type, rsd->ctx, st);

	v = saved_value_lookup(NULL, cpu, false, type, rsd->ctx, st, rsd->cgrp);

	if (!v)

		return 0.0;
@@ -805,7 +815,8 @@ static int prepare_metric(struct evsel **metric_events, 
			scale = 1e-9;

		} else {

			v = saved_value_lookup(metric_events[i], cpu, false,

					       STAT_NONE, 0, st);

					       STAT_NONE, 0, st,

					       metric_events[i]->cgrp);

			if (!v)

				break;

			stats = &v->stats;
@@ -933,6 +944,7 @@ void perf_stat__print_shadow_stats(struct perf_stat_config *config, 
	const char *color = NULL;

	struct runtime_stat_data rsd = {

		.ctx = evsel_context(evsel),

		.cgrp = evsel->cgrp,

	};

	struct metric_event *me;

	int num = 1;