perf evlist: No need to setup affinities when disabling events for pid targets

When the target is a pid, not started by 'perf stat' we need to disable
the events, and in that case there is no need to setup affinities as we
use a dummy CPU map, with just one entry set to -1.

So stop doing it to avoid this needless call to sched_getaffinity():

  # strace -ke sched_getaffinity perf stat -e cycles -p 241957 sleep 1
  <SNIP>
  sched_getaffinity(0, 512, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31]) = 8
   > /usr/lib64/libc-2.33.so(sched_getaffinity@@GLIBC_2.3.4+0x1a) [0xe6eea]
   > /var/home/acme/bin/perf(affinity__setup+0x6a) [0x532a2a]
   > /var/home/acme/bin/perf(__evlist__disable.constprop.0+0x27) [0x4b9827]
   > /var/home/acme/bin/perf(cmd_stat+0x29b5) [0x431725]
   > /var/home/acme/bin/perf(run_builtin+0x6a) [0x4a2cfa]
   > /var/home/acme/bin/perf(main+0x612) [0x40f8c2]
   > /usr/lib64/libc-2.33.so(__libc_start_main+0xd4) [0x27b74]
   > /var/home/acme/bin/perf(_start+0x2d) [0x40fadd]
  <SNIP>

Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20220117160931.1191712-5-acme@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index ae6d436..eaad04e 100644 (file)
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -430,15 +430,19 @@ static void __evlist__disable(struct evlist *evlist, char *evsel_name)
 {
        struct evsel *pos;
        struct evlist_cpu_iterator evlist_cpu_itr;
-       struct affinity affinity;
+       struct affinity saved_affinity, *affinity = NULL;
        bool has_imm = false;
 
-       if (affinity__setup(&affinity) < 0)
-               return;
+       // See explanation in evlist__close()
+       if (!cpu_map__is_dummy(evlist->core.cpus)) {
+               if (affinity__setup(&saved_affinity) < 0)
+                       return;
+               affinity = &saved_affinity;
+       }
 
        /* Disable 'immediate' events last */
        for (int imm = 0; imm <= 1; imm++) {
-               evlist__for_each_cpu(evlist_cpu_itr, evlist, &affinity) {
+               evlist__for_each_cpu(evlist_cpu_itr, evlist, affinity) {
                        pos = evlist_cpu_itr.evsel;
                        if (evsel__strcmp(pos, evsel_name))
                                continue;
@@ -454,7 +458,7 @@ static void __evlist__disable(struct evlist *evlist, char *evsel_name)
                        break;
        }
 
-       affinity__cleanup(&affinity);
+       affinity__cleanup(affinity);
        evlist__for_each_entry(evlist, pos) {
                if (evsel__strcmp(pos, evsel_name))
                        continue;