libperf: Warn when exceeding MAX_NR_CPUS in cpumap

Display a warning when attempting to profile more than MAX_NR_CPU CPUs.
This patch should not change any behavior.

Signed-off-by: Kyle Meyer <kyle.meyer@hpe.com>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russ Anderson <russ.anderson@hpe.com>
Link: http://lore.kernel.org/lkml/20190827214352.94272-8-meyerk@stormcage.eag.rdlabs.hpecorp.net
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/lib/cpumap.c b/tools/perf/lib/cpumap.c
index 2834753..1f0e6f3 100644 (file)
--- a/tools/perf/lib/cpumap.c
+++ b/tools/perf/lib/cpumap.c
@@ -100,6 +100,9 @@ struct perf_cpu_map *perf_cpu_map__read(FILE *file)
                if (prev >= 0) {
                        int new_max = nr_cpus + cpu - prev - 1;
 
+                       WARN_ONCE(new_max >= MAX_NR_CPUS, "Perf can support %d CPUs. "
+                                                         "Consider raising MAX_NR_CPUS\n", MAX_NR_CPUS);
+
                        if (new_max >= max_entries) {
                                max_entries = new_max + MAX_NR_CPUS / 2;
                                tmp = realloc(tmp_cpus, max_entries * sizeof(int));
@@ -192,6 +195,9 @@ struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list)
                        end_cpu = start_cpu;
                }
 
+               WARN_ONCE(end_cpu >= MAX_NR_CPUS, "Perf can support %d CPUs. "
+                                                 "Consider raising MAX_NR_CPUS\n", MAX_NR_CPUS);
+
                for (; start_cpu <= end_cpu; start_cpu++) {
                        /* check for duplicates */
                        for (i = 0; i < nr_cpus; i++)