[PATCH v3 4/5] perf evlist: Respect all_cpus when setting user_requested_cpus

[Ian Rogers]

If all_cpus is calculated it represents the merge/union of all
evsel cpu maps. By default user_requested_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_requested_cpus. Metrics printed
without aggregation and with metric-only, in print_no_aggr_metric,
iterate over user_requested_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 2 socket 36 core 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_requested_cpus not be a subset of
all_cpus is preferential so that wasted work isn't done elsewhere
user_requested_cpus is used. The change modifies user_requested_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 at google.com>
---
 tools/perf/util/evlist.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 52ea004ba01e..196d57b905a0 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1036,6 +1036,13 @@ int evlist__create_maps(struct evlist *evlist, struct target *target)
 	if (!cpus)
 		goto out_delete_threads;
 
+	if (evlist->core.all_cpus) {
+		struct perf_cpu_map *tmp;
+
+		tmp = perf_cpu_map__intersect(cpus, evlist->core.all_cpus);
+		perf_cpu_map__put(cpus);
+		cpus = tmp;
+	}
 	evlist->core.has_user_cpus = !!target->cpu_list && !target->hybrid;
 
 	perf_evlist__set_maps(&evlist->core, cpus, threads);
-- 
2.35.1.1178.g4f1659d476-goog