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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: Namhyung 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: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2020-12-16 18:05:56 +09:00 committed by Arnaldo Carvalho de Melo
parent 6fd99b7f62
commit 48859e5293
1 changed files with 19 additions and 0 deletions
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19
tools/lib/api/fs/cgroup.c
View File

@ -8,6 +8,14 @@
#include <string.h> #include <string.h>
#include "fs.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) int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
{ {
FILE *fp; FILE *fp;
@ -16,6 +24,14 @@ int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
char *p, *path; char *p, *path;
char mountpoint[PATH_MAX]; 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"); fp = fopen("/proc/mounts", "r");
if (!fp) if (!fp)
return -1; return -1;
@ -75,6 +91,9 @@ int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
free(line); free(line);
fclose(fp); fclose(fp);
strncpy(cached.subsys, subsys, sizeof(cached.subsys) - 1);
strcpy(cached.mountpoint, mountpoint);
if (mountpoint[0] && strlen(mountpoint) < maxlen) { if (mountpoint[0] && strlen(mountpoint) < maxlen) {
strcpy(buf, mountpoint); strcpy(buf, mountpoint);
return 0; return 0;