netdev - [PATCH 5/5] perf evlist: Respect all_cpus when setting user

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Date:   Sun, 27 Mar 2022 23:24:14 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Kajol Jain <kjain@...ux.ibm.com>,
        James Clark <james.clark@....com>,
        German Gomez <german.gomez@....com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Riccardo Mancini <rickyman7@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Alexey Bayduraev <alexey.v.bayduraev@...ux.intel.com>,
        Alexander Antonov <alexander.antonov@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Cc:     Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH 5/5] perf evlist: Respect all_cpus when setting user_cpus

If all_cpus is calculated it represents the merge/union of all
evsel cpu maps. By default user_cpus is computed to be the online
CPUs. For uncore events, it is often the case currently that
all_cpus is a subset of user_cpus. Metrics printed without
aggregation and with metric-only, in print_no_aggr_metric,
iterate over user_cpus assuming every CPU has a metric to
print. For each CPU the prefix is printed, but then if the
evsel's cpus doesn't contain anything you get an empty line like
the following on a SkylakeX:

```
$ perf stat -A -M DRAM_BW_Use -a --metric-only -I 1000
     1.000453137 CPU0                       0.00
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137 CPU18                      0.00
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     1.000453137
     2.003717143 CPU0                       0.00
...
```

While it is possible to be lazier in printing the prefix and
trailing newline, having user_cpus not be a subset of all_cpus is
preferential so that wasted work isn't done elsewhere user_cpus
is used. The change modifies user_cpus to be the intersection of
user specified CPUs, or default all online CPUs, with the CPUs
computed through the merge of all evsel cpu maps.

New behavior:
```
$ perf stat -A -M DRAM_BW_Use -a --metric-only -I 1000
     1.001086325 CPU0                       0.00
     1.001086325 CPU18                      0.00
     2.003671291 CPU0                       0.00
     2.003671291 CPU18                      0.00
...
```

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/evlist.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index d335fb713f5e..91bbb66b7e9a 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1036,6 +1036,8 @@ int evlist__create_maps(struct evlist *evlist, struct target *target)
 	if (!cpus)
 		goto out_delete_threads;
 
+	if (evlist->core.all_cpus)
+		cpus = perf_cpu_map__intersect(cpus, evlist->core.all_cpus);
 	evlist->core.has_user_cpus = !!target->cpu_list && !target->hybrid;
 
 	perf_evlist__set_maps(&evlist->core, cpus, threads);
-- 
2.35.1.1021.g381101b075-goog