Commit 48859e52 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
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tools api fs: Cache cgroupfs mount point 



Currently it parses the /proc file everytime it opens a file in the
cgroupfs.  Save the last result to avoid it (assuming it won't be
changed between the accesses).

Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20201216090556.813996-3-namhyung@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 6fd99b7f

tools/lib/api/fs/cgroup.c

+19 −0
Original line number Diff line number Diff line
@@ -8,6 +8,14 @@ 
#include <string.h>

#include "fs.h"



struct cgroupfs_cache_entry {

	char	subsys[32];

	char	mountpoint[PATH_MAX];

};



/* just cache last used one */

static struct cgroupfs_cache_entry cached;



int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)

{

	FILE *fp;
@@ -16,6 +24,14 @@ 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);

			return 0;

		}

		return -1;

	}



	fp = fopen("/proc/mounts", "r");

	if (!fp)

		return -1;
@@ -75,6 +91,9 @@ 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 (mountpoint[0] && strlen(mountpoint) < maxlen) {

		strcpy(buf, mountpoint);

		return 0;