perf evsel: Introduce event fallback method

The only fallback right now is for HW cpu-cycles -> SW cpu-clock, that
was done in the same way in both 'top' and 'record'.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-58l1mgibh9oa9m0pd3fasxa5@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index ee6ee3f45c2a..0c88e5c12dab 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1378,3 +1378,31 @@ int perf_evsel__fprintf(struct perf_evsel *evsel,
         fputc('\n', fp);
         return ++printed;
 }
+
+bool perf_evsel__fallback(struct perf_evsel *evsel, int err,
+                          char *msg, size_t msgsize)
+{
+        if ((err == ENOENT || err == ENXIO) &&
+            evsel->attr.type   == PERF_TYPE_HARDWARE &&
+            evsel->attr.config == PERF_COUNT_HW_CPU_CYCLES) {
+                /*
+                 * If it's cycles then fall back to hrtimer based
+                 * cpu-clock-tick sw counter, which is always available even if
+                 * no PMU support.
+                 *
+                 * PPC returns ENXIO until 2.6.37 (behavior changed with commit
+                 * b0a873e).
+                 */
+                scnprintf(msg, msgsize, "%s",
+"The cycles event is not supported, trying to fall back to cpu-clock-ticks");
+
+                evsel->attr.type   = PERF_TYPE_SOFTWARE;
+                evsel->attr.config = PERF_COUNT_SW_CPU_CLOCK;
+
+                free(evsel->name);
+                evsel->name = NULL;
+                return true;
+        }
+
+        return false;
+}