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perf stat: Take cgroups into account for shadow stats

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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: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri 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: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2021-01-15 16:11:39 +09:00 committed by Arnaldo Carvalho de Melo
parent 3ff1e7180a
commit a1bf23052b
1 changed files with 19 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
tools/perf/util/stat-shadow.c
View File

@ -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;