linux-kernel - [PATCH v2 14/16] tools api fs: Dynamically allocate cgroupfs mount point cache

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Date:   Fri, 26 May 2023 11:33:59 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>,
        Ross Zwisler <zwisler@...omium.org>,
        Leo Yan <leo.yan@...aro.org>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Yang Jihong <yangjihong1@...wei.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: [PATCH v2 14/16] tools api fs: Dynamically allocate cgroupfs mount
 point cache

Move the cgroupfs_cache_entry 4128 byte array out of .bss.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/lib/api/fs/cgroup.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/tools/lib/api/fs/cgroup.c b/tools/lib/api/fs/cgroup.c
index 1573dae4259d..250629a09423 100644
--- a/tools/lib/api/fs/cgroup.c
+++ b/tools/lib/api/fs/cgroup.c
@@ -14,7 +14,7 @@ struct cgroupfs_cache_entry {
 };
 
 /* just cache last used one */
-static struct cgroupfs_cache_entry cached;
+static struct cgroupfs_cache_entry *cached;
 
 int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
 {
@@ -24,9 +24,9 @@ int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
 	char *p, *path;
 	char mountpoint[PATH_MAX];
 
-	if (!strcmp(cached.subsys, subsys)) {
-		if (strlen(cached.mountpoint) < maxlen) {
-			strcpy(buf, cached.mountpoint);
+	if (cached && !strcmp(cached->subsys, subsys)) {
+		if (strlen(cached->mountpoint) < maxlen) {
+			strcpy(buf, cached->mountpoint);
 			return 0;
 		}
 		return -1;
@@ -91,8 +91,13 @@ int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
 	free(line);
 	fclose(fp);
 
-	strncpy(cached.subsys, subsys, sizeof(cached.subsys) - 1);
-	strcpy(cached.mountpoint, mountpoint);
+	if (!cached)
+		cached = calloc(1, sizeof(*cached));
+
+	if (cached) {
+		strncpy(cached->subsys, subsys, sizeof(cached->subsys) - 1);
+		strcpy(cached->mountpoint, mountpoint);
+	}
 
 	if (mountpoint[0] && strlen(mountpoint) < maxlen) {
 		strcpy(buf, mountpoint);
-- 
2.41.0.rc0.172.g3f132b7071-goog