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: 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
Arnaldo Carvalho de Melo
parent
3ff1e7180a
commit
a1bf23052b
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@ -8,6 +8,7 @@
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#include "evlist.h"
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#include "expr.h"
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#include "metricgroup.h"
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#include "cgroup.h"
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#include <linux/zalloc.h>
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/*
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@ -28,6 +29,7 @@ struct saved_value {
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enum stat_type type;
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int ctx;
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int cpu;
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struct cgroup *cgrp;
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struct runtime_stat *stat;
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struct stats stats;
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u64 metric_total;
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@ -57,6 +59,9 @@ static int saved_value_cmp(struct rb_node *rb_node, const void *entry)
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if (a->ctx != b->ctx)
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return a->ctx - b->ctx;
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if (a->cgrp != b->cgrp)
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return (char *)a->cgrp < (char *)b->cgrp ? -1 : +1;
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if (a->evsel == NULL && b->evsel == NULL) {
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if (a->stat == b->stat)
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return 0;
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@ -100,7 +105,8 @@ static struct saved_value *saved_value_lookup(struct evsel *evsel,
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bool create,
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enum stat_type type,
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int ctx,
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struct runtime_stat *st)
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struct runtime_stat *st,
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struct cgroup *cgrp)
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{
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struct rblist *rblist;
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struct rb_node *nd;
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@ -110,6 +116,7 @@ static struct saved_value *saved_value_lookup(struct evsel *evsel,
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.type = type,
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.ctx = ctx,
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.stat = st,
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.cgrp = cgrp,
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};
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rblist = &st->value_list;
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@ -197,6 +204,7 @@ void perf_stat__reset_shadow_per_stat(struct runtime_stat *st)
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struct runtime_stat_data {
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int ctx;
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struct cgroup *cgrp;
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};
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static void update_runtime_stat(struct runtime_stat *st,
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@ -205,7 +213,7 @@ static void update_runtime_stat(struct runtime_stat *st,
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struct runtime_stat_data *rsd)
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{
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struct saved_value *v = saved_value_lookup(NULL, cpu, true, type,
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rsd->ctx, st);
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rsd->ctx, st, rsd->cgrp);
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if (v)
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update_stats(&v->stats, count);
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@ -223,6 +231,7 @@ void perf_stat__update_shadow_stats(struct evsel *counter, u64 count,
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struct saved_value *v;
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struct runtime_stat_data rsd = {
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.ctx = evsel_context(counter),
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.cgrp = counter->cgrp,
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};
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count *= counter->scale;
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@ -290,13 +299,14 @@ void perf_stat__update_shadow_stats(struct evsel *counter, u64 count,
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update_runtime_stat(st, STAT_APERF, cpu, count, &rsd);
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if (counter->collect_stat) {
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v = saved_value_lookup(counter, cpu, true, STAT_NONE, 0, st);
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v = saved_value_lookup(counter, cpu, true, STAT_NONE, 0, st,
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rsd.cgrp);
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update_stats(&v->stats, count);
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if (counter->metric_leader)
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v->metric_total += count;
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} else if (counter->metric_leader) {
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v = saved_value_lookup(counter->metric_leader,
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cpu, true, STAT_NONE, 0, st);
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cpu, true, STAT_NONE, 0, st, rsd.cgrp);
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v->metric_total += count;
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v->metric_other++;
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}
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@ -438,7 +448,7 @@ static double runtime_stat_avg(struct runtime_stat *st,
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{
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struct saved_value *v;
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v = saved_value_lookup(NULL, cpu, false, type, rsd->ctx, st);
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v = saved_value_lookup(NULL, cpu, false, type, rsd->ctx, st, rsd->cgrp);
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if (!v)
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return 0.0;
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@ -451,7 +461,7 @@ static double runtime_stat_n(struct runtime_stat *st,
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{
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struct saved_value *v;
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v = saved_value_lookup(NULL, cpu, false, type, rsd->ctx, st);
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v = saved_value_lookup(NULL, cpu, false, type, rsd->ctx, st, rsd->cgrp);
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if (!v)
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return 0.0;
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@ -805,7 +815,8 @@ static int prepare_metric(struct evsel **metric_events,
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scale = 1e-9;
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} else {
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v = saved_value_lookup(metric_events[i], cpu, false,
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STAT_NONE, 0, st);
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STAT_NONE, 0, st,
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metric_events[i]->cgrp);
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if (!v)
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break;
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stats = &v->stats;
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@ -933,6 +944,7 @@ void perf_stat__print_shadow_stats(struct perf_stat_config *config,
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const char *color = NULL;
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struct runtime_stat_data rsd = {
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.ctx = evsel_context(evsel),
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.cgrp = evsel->cgrp,
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};
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struct metric_event *me;
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int num = 1;
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