[RFC PATCH 3/3] perf: util: only open events on CPUs an evsel permits

[Mark Rutland]

In systems with heterogeneous CPU PMUs, it's possible for each evsel to
cover a distinct set of CPUs, and hence the cpu_map associated with each
evsel may have a distinct idx<->id mapping. Any of these may be distinct from
the evlist's cpu map.

Events can be tied to the same fd so long as they use the same per-cpu
ringbuffer (i.e. so long as they are on the same CPU). To acquire the
correct FDs, we must compare the Linux logical IDs rather than the evsel
or evlist indices.

This path adds logic to perf_evlist__mmap_per_evsel to handle this,
translating IDs as required. As PMUs may cover a subset of CPUs from the
evlist, we skip the CPUs a PMU cannot handle.

Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: He Kuang <hekuang@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
 tools/perf/util/evlist.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index e82ba90..0b5b1be 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -984,17 +984,24 @@ static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
 }
 
 static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
-				       struct mmap_params *mp, int cpu,
+				       struct mmap_params *mp, int cpu_idx,
 				       int thread, int *output)
 {
 	struct perf_evsel *evsel;
+	int evlist_cpu = cpu_map__cpu(evlist->cpus, cpu_idx);
 
 	evlist__for_each(evlist, evsel) {
 		int fd;
+		int cpu;
 
 		if (evsel->system_wide && thread)
 			continue;
 
+		if (!cpu_map__has(evsel->cpus, evlist_cpu))
+			continue;
+
+		cpu = cpu_map__idx(evsel->cpus, evlist_cpu);
+
 		fd = FD(evsel, cpu, thread);
 
 		if (*output == -1) {
-- 
1.9.1