linux-kernel - [RFC PATCH v1 20/37] perf evsel: separate rlimit increase from evsel__open

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Message-Id: <2f256de8ec37b9809a5cef73c2fa7bce416af5d3.1629490974.git.rickyman7@gmail.com>
Date:   Sat, 21 Aug 2021 11:19:26 +0200
From:   Riccardo Mancini <rickyman7@...il.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ian Rogers <irogers@...gle.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Riccardo Mancini <rickyman7@...il.com>
Subject: [RFC PATCH v1 20/37] perf evsel: separate rlimit increase from evsel__open_cpu

This is a preparatory patch for the following patches with the goal to
separate from evlist__open_cpu the actual opening (which could be
performed in parallel), from the existing fallback mechanisms, which
should be handled sequentially.

This patch separates the rlimit increase from evsel__open_cpu.

Signed-off-by: Riccardo Mancini <rickyman7@...il.com>
---
 tools/perf/util/evsel.c | 50 ++++++++++++++++++++++++-----------------
 tools/perf/util/evsel.h |  3 +++
 2 files changed, 33 insertions(+), 20 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index c393bd992322d925..916930ea31450265 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1931,13 +1931,40 @@ bool evsel__detect_missing_features(struct evsel *evsel)
 	}
 }
 
+bool evsel__increase_rlimit(enum rlimit_action *set_rlimit)
+{
+	int old_errno;
+	struct rlimit l;
+
+	if (*set_rlimit < INCREASED_MAX) {
+
+		old_errno = errno;
+		if (getrlimit(RLIMIT_NOFILE, &l) == 0) {
+			if (*set_rlimit == NO_CHANGE)
+				l.rlim_cur = l.rlim_max;
+			else {
+				l.rlim_cur = l.rlim_max + 1000;
+				l.rlim_max = l.rlim_cur;
+			}
+			if (setrlimit(RLIMIT_NOFILE, &l) == 0) {
+				(*set_rlimit) += 1;
+				errno = old_errno;
+				return true;
+			}
+		}
+		errno = old_errno;
+	}
+
+	return false;
+}
+
 static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 		struct perf_thread_map *threads,
 		int start_cpu, int end_cpu)
 {
 	int cpu, thread, nthreads;
 	int pid = -1, err, old_errno;
-	enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;
+	enum rlimit_action set_rlimit = NO_CHANGE;
 
 	err = __evsel__prepare_open(evsel, cpus, threads);
 	if (err)
@@ -2046,25 +2073,8 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	 * perf stat needs between 5 and 22 fds per CPU. When we run out
 	 * of them try to increase the limits.
 	 */
-	if (err == -EMFILE && set_rlimit < INCREASED_MAX) {
-		struct rlimit l;
-
-		old_errno = errno;
-		if (getrlimit(RLIMIT_NOFILE, &l) == 0) {
-			if (set_rlimit == NO_CHANGE)
-				l.rlim_cur = l.rlim_max;
-			else {
-				l.rlim_cur = l.rlim_max + 1000;
-				l.rlim_max = l.rlim_cur;
-			}
-			if (setrlimit(RLIMIT_NOFILE, &l) == 0) {
-				set_rlimit++;
-				errno = old_errno;
-				goto retry_open;
-			}
-		}
-		errno = old_errno;
-	}
+	if (err == -EMFILE && evsel__increase_rlimit(&set_rlimit))
+		goto retry_open;
 
 	if (err != -EINVAL || cpu > 0 || thread > 0)
 		goto out_close;
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index a83fb7f69b1ead73..bf9abd9a5cbf9852 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -290,6 +290,9 @@ int evsel__prepare_open(struct evsel *evsel, struct perf_cpu_map *cpus,
 		struct perf_thread_map *threads);
 bool evsel__detect_missing_features(struct evsel *evsel);
 
+enum rlimit_action { NO_CHANGE, SET_TO_MAX, INCREASED_MAX };
+bool evsel__increase_rlimit(enum rlimit_action *set_rlimit);
+
 struct perf_sample;
 
 void *evsel__rawptr(struct evsel *evsel, struct perf_sample *sample, const char *name);
-- 
2.31.1