perf evsel: State in the default event name if attr.exclude_kernel is set

Commit-ID:  ede5626d303b721dd02246a3850380943c24e380
Gitweb:     http://git.kernel.org/tip/ede5626d303b721dd02246a3850380943c24e380
Author:     Arnaldo Carvalho de Melo <[email protected]>
AuthorDate: Mon, 10 Jul 2017 16:19:25 -0300
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 10 Jul 2017 16:19:25 -0300

perf evsel: State in the default event name if attr.exclude_kernel is set

When no event is specified perf will use the "cycles" hardware event with the highest precision available in the processor, and excluding kernel events for non-root users, so make that clear in the event name by setting the "u" event modifier, i.e. "cycles:upp".

E.g.:

The default for root:

  # perf record usleep 1
  # perf evlist -v
  cycles:ppp: ..., precise_ip: 3, exclude_kernel: 0, ...
  #

And for !root:

  $ perf record usleep 1
  $ perf evlist -v
  cycles:uppp: ... , precise_ip: 3, exclude_kernel: 1, ...
  $

---
 tools/perf/util/evsel.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

index f2a1876..413f74d 100644
@@ -298,8 +298,10 @@ struct perf_evsel *perf_evsel__new_cycles(void)
 		goto out;
 
 	/* use asprintf() because free(evsel) assumes name is allocated */
-	if (asprintf(&evsel->name, "cycles%.*s",
-		     attr.precise_ip ? attr.precise_ip + 1 : 0, ":ppp") < 0)
+	if (asprintf(&evsel->name, "cycles%s%s%.*s",
+		     (attr.precise_ip || attr.exclude_kernel) ? ":" : "",
+		     attr.exclude_kernel ? "u" : "",
+		     attr.precise_ip ? attr.precise_ip + 1 : 0, "ppp") < 0)
 		goto error_free;
 out:
 	return evsel;