perf kmem: Show warning when trying to run stat without record

Sometimes one can mistakenly run 'perf kmem stat' without running 'perf
kmem record' before or with a different configuration like recording
--slab and stat --page.  Show a warning message like the one below to
inform the user:

  # perf kmem stat --page --caller
  No page allocation events found.  Have you run 'perf kmem record --page'?

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/1430837572-31395-1-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-kmem.c b/tools/perf/builtin-kmem.c
index 828b728..e628bf1 100644 (file)
--- a/tools/perf/builtin-kmem.c
+++ b/tools/perf/builtin-kmem.c
@@ -1882,6 +1882,7 @@ int cmd_kmem(int argc, const char **argv, const char *prefix __maybe_unused)
        };
        struct perf_session *session;
        int ret = -1;
+       const char errmsg[] = "No %s allocation events found.  Have you run 'perf kmem record --%s'?\n";
 
        perf_config(kmem_config, NULL);
        argc = parse_options_subcommand(argc, argv, kmem_options,
@@ -1908,11 +1909,21 @@ int cmd_kmem(int argc, const char **argv, const char *prefix __maybe_unused)
        if (session == NULL)
                return -1;
 
+       if (kmem_slab) {
+               if (!perf_evlist__find_tracepoint_by_name(session->evlist,
+                                                         "kmem:kmalloc")) {
+                       pr_err(errmsg, "slab", "slab");
+                       return -1;
+               }
+       }
+
        if (kmem_page) {
-               struct perf_evsel *evsel = perf_evlist__first(session->evlist);
+               struct perf_evsel *evsel;
 
-               if (evsel == NULL || evsel->tp_format == NULL) {
-                       pr_err("invalid event found.. aborting\n");
+               evsel = perf_evlist__find_tracepoint_by_name(session->evlist,
+                                                            "kmem:mm_page_alloc");
+               if (evsel == NULL) {
+                       pr_err(errmsg, "page", "page");
                        return -1;
                }