linux-kernel - [RFC PATCH v1 1/3] perf evsel: Don't open tool events

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Message-Id: <20240425223406.471120-2-irogers@google.com>
Date: Thu, 25 Apr 2024 15:34:04 -0700
From: Ian Rogers <irogers@...gle.com>
To: weilin.wang@...el.com, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, Ze Gao <zegao2021@...il.com>, 
	Leo Yan <leo.yan@...ux.dev>, Ravi Bangoria <ravi.bangoria@....com>, 
	Dmitrii Dolgov <9erthalion6@...il.com>, Song Liu <song@...nel.org>, 
	James Clark <james.clark@....com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH v1 1/3] perf evsel: Don't open tool events

Tool events are set up as software dummy events. Don't open them to
save some work and a file descriptor. The evsel's fds are initialized
to -1, so it suffices to just early return.
---
 tools/perf/util/evsel.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 3536404e9447..2743d40665ff 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2005,6 +2005,11 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	int pid = -1, err, old_errno;
 	enum rlimit_action set_rlimit = NO_CHANGE;
 
+	if (evsel__is_tool(evsel)) {
+		/* Tool events are set up as dummy but don't need opening. */
+		return 0;
+	}
+
 	err = __evsel__prepare_open(evsel, cpus, threads);
 	if (err)
 		return err;
-- 
2.44.0.769.g3c40516874-goog