Re: [PATCH v5 10/12] perf util: Reuse thread_map__new_by_uid to enumerate threads from /proc

[Arnaldo Carvalho de Melo]

Em Fri, Dec 01, 2017 at 06:57:34PM +0800, Jin Yao escreveu:
> Perf already has a function thread_map__new_by_uid() which can
> enumerate all threads from /proc by uid.
> 
> This patch creates a static function enumerate_threads() which
> reuses the common code in thread_map__new_by_uid() to enumerate
> threads from /proc.
> 
> The enumerate_threads() is shared by thread_map__new_by_uid()
> and a new function thread_map__new_threads().
> 
> The new function thread_map__new_threads() is called to enumerate
> all threads from /proc.
> 
> Signed-off-by: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
> ---
>  tools/perf/tests/thread-map.c |  2 +-
>  tools/perf/util/evlist.c      |  3 ++-
>  tools/perf/util/thread_map.c  | 19 ++++++++++++++++---
>  tools/perf/util/thread_map.h  |  3 ++-
>  4 files changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/tests/thread-map.c b/tools/perf/tests/thread-map.c
> index dbcb6a1..4de1939 100644
> --- a/tools/perf/tests/thread-map.c
> +++ b/tools/perf/tests/thread-map.c
> @@ -105,7 +105,7 @@ int test__thread_map_remove(struct test *test __maybe_unused, int subtest __mayb
>  	TEST_ASSERT_VAL("failed to allocate map string",
>  			asprintf(&str, "%d,%d", getpid(), getppid()) >= 0);
>  
> -	threads = thread_map__new_str(str, NULL, 0);
> +	threads = thread_map__new_str(str, NULL, 0, false);
>  
>  	TEST_ASSERT_VAL("failed to allocate thread_map",
>  			threads);
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 199bb82..05b8f2b 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -1102,7 +1102,8 @@ int perf_evlist__create_maps(struct perf_evlist *evlist, struct target *target)
>  	struct cpu_map *cpus;
>  	struct thread_map *threads;
>  
> -	threads = thread_map__new_str(target->pid, target->tid, target->uid);
> +	threads = thread_map__new_str(target->pid, target->tid, target->uid,
> +				      target->per_thread);
>  
>  	if (!threads)
>  		return -1;
> diff --git a/tools/perf/util/thread_map.c b/tools/perf/util/thread_map.c
> index be0d5a7..5672268 100644
> --- a/tools/perf/util/thread_map.c
> +++ b/tools/perf/util/thread_map.c
> @@ -92,7 +92,7 @@ struct thread_map *thread_map__new_by_tid(pid_t tid)
>  	return threads;
>  }
>  
> -struct thread_map *thread_map__new_by_uid(uid_t uid)
> +static struct thread_map *enumerate_threads(uid_t uid)
>  {
>  	DIR *proc;
>  	int max_threads = 32, items, i;
> @@ -124,7 +124,7 @@ struct thread_map *thread_map__new_by_uid(uid_t uid)
>  		if (stat(path, &st) != 0)
>  			continue;

Look, for the case where you want all threads enumerated you will incur
the above stat() cost for all of them and will not use it at all...

And new_threads() seems vague, I'm using the ter used by 'perf record'
for system wide sampling, see the patch below:

diff --git a/tools/perf/util/thread_map.c b/tools/perf/util/thread_map.c
index be0d5a736dea..79d11bd4543a 100644
--- a/tools/perf/util/thread_map.c
+++ b/tools/perf/util/thread_map.c
@@ -92,7 +92,7 @@ struct thread_map *thread_map__new_by_tid(pid_t tid)
 	return threads;
 }
 
-struct thread_map *thread_map__new_by_uid(uid_t uid)
+static struct thread_map *__thread_map__new_all_cpus(uid_t uid)
 {
 	DIR *proc;
 	int max_threads = 32, items, i;
@@ -113,7 +113,6 @@ struct thread_map *thread_map__new_by_uid(uid_t uid)
 	while ((dirent = readdir(proc)) != NULL) {
 		char *end;
 		bool grow = false;
-		struct stat st;
 		pid_t pid = strtol(dirent->d_name, &end, 10);
 
 		if (*end) /* only interested in proper numerical dirents */
@@ -121,11 +120,12 @@ struct thread_map *thread_map__new_by_uid(uid_t uid)
 
 		snprintf(path, sizeof(path), "/proc/%s", dirent->d_name);
 
-		if (stat(path, &st) != 0)
-			continue;
+		if (uid != UID_MAX) {
+			struct stat st;
 
-		if (st.st_uid != uid)
-			continue;
+			if (stat(path, &st) != 0 || st.st_uid != uid)
+				continue;
+		}
 
 		snprintf(path, sizeof(path), "/proc/%d/task", pid);
 		items = scandir(path, &namelist, filter, NULL);
@@ -178,6 +178,16 @@ struct thread_map *thread_map__new_by_uid(uid_t uid)
 	goto out_closedir;
 }
 
+struct thread_map *thread_map__new_all_cpus(void)
+{
+	return __thread__new_all_cpus(UID_MAX);
+}
+
+struct thread_map *thread_map__new_by_uid(uid_t uid)
+{
+	return __thread__new_all_cpus(uid);
+}
+
 struct thread_map *thread_map__new(pid_t pid, pid_t tid, uid_t uid)
 {
 	if (pid != -1)
diff --git a/tools/perf/util/thread_map.h b/tools/perf/util/thread_map.h
index f15803985435..07a765fb22bb 100644
--- a/tools/perf/util/thread_map.h
+++ b/tools/perf/util/thread_map.h
@@ -23,6 +23,7 @@ struct thread_map *thread_map__new_dummy(void);
 struct thread_map *thread_map__new_by_pid(pid_t pid);
 struct thread_map *thread_map__new_by_tid(pid_t tid);
 struct thread_map *thread_map__new_by_uid(uid_t uid);
+struct thread_map *thread_map__new_all_cpus(void);
 struct thread_map *thread_map__new(pid_t pid, pid_t tid, uid_t uid);
 struct thread_map *thread_map__new_event(struct thread_map_event *event);