From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>, Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
LKML <linux-kernel@vger.kernel.org>,
Stephane Eranian <eranian@google.com>,
Ian Rogers <irogers@google.com>, Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH 3/3] tools/lib/fs: Cache cgroupfs mount point
Date: Tue, 29 Dec 2020 08:51:58 -0300 [thread overview]
Message-ID: <20201229115158.GH521329@kernel.org> (raw)
In-Reply-To: <20201216090556.813996-3-namhyung@kernel.org>
Em Wed, Dec 16, 2020 at 06:05:56PM +0900, Namhyung Kim escreveu:
> 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).
Which is the most likely case, but can't we use something like inotify
to detect that and bail out or warn the user?
- Arnaldo
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
> tools/lib/api/fs/cgroup.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/tools/lib/api/fs/cgroup.c b/tools/lib/api/fs/cgroup.c
> index 262a4229e293..1573dae4259d 100644
> --- a/tools/lib/api/fs/cgroup.c
> +++ b/tools/lib/api/fs/cgroup.c
> @@ -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;
> --
> 2.29.2.684.gfbc64c5ab5-goog
>
--
- Arnaldo
next prev parent reply other threads:[~2020-12-29 11:52 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-16 9:05 [PATCH 1/3] tools/lib/fs: Prefer cgroup v1 path Namhyung Kim
2020-12-16 9:05 ` [PATCH 2/3] tools/lib/fs: Diet cgroupfs_find_mountpoint() Namhyung Kim
2020-12-28 8:31 ` Jiri Olsa
2020-12-29 5:27 ` Namhyung Kim
2020-12-29 9:39 ` Jiri Olsa
2020-12-16 9:05 ` [PATCH 3/3] tools/lib/fs: Cache cgroupfs mount point Namhyung Kim
2020-12-29 11:51 ` Arnaldo Carvalho de Melo [this message]
2021-01-06 1:33 ` Namhyung Kim
2021-01-08 5:51 ` Namhyung Kim
2021-01-21 4:33 ` Namhyung Kim
2021-02-17 12:58 ` Arnaldo Carvalho de Melo
2021-02-19 10:05 ` Namhyung Kim
2021-02-19 11:37 ` Arnaldo Carvalho de Melo
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