Re: [PATCH] libperf: Add API for allocating new thread map

[Jiri Olsa]

On Thu, Feb 10, 2022 at 10:52:25AM +0200, Tzvetomir Stoyanov (VMware) wrote:
> The existing API perf_thread_map__new_dummy() allocates new thread map
> for one thread. I couldn't find a way to reallocate the map with more
> threads, or to allocate a new map for more than one thread. Having
> multiple threads in a thread map is essential for some use cases.
> That's why a new API is proposed, which allocates a new thread map
> for given number of threads:
>  perf_thread_map__new()

I'm ok with that, just wondering if we should call it 'perf_thread_map__new_nr'
because we already have perf_cpu_map__new(const char *cpu_list) so
it might be better to keep perf_cpu_map and perf_thread_map in sync

Arnaldo, thoughts on this?

jirka

> 
> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@xxxxxxxxx>
> ---
>  tools/lib/perf/Documentation/libperf.txt |  1 +
>  tools/lib/perf/include/perf/threadmap.h  |  1 +
>  tools/lib/perf/libperf.map               |  1 +
>  tools/lib/perf/tests/test-threadmap.c    | 27 ++++++++++++++++++++++++
>  tools/lib/perf/threadmap.c               | 15 +++++++++----
>  5 files changed, 41 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/lib/perf/Documentation/libperf.txt b/tools/lib/perf/Documentation/libperf.txt
> index 32c5051c24eb..9cbd41c29bff 100644
> --- a/tools/lib/perf/Documentation/libperf.txt
> +++ b/tools/lib/perf/Documentation/libperf.txt
> @@ -62,6 +62,7 @@ SYNOPSIS
>    struct perf_thread_map;
>  
>    struct perf_thread_map *perf_thread_map__new_dummy(void);
> +  struct perf_thread_map *perf_thread_map__new(int nr);
>  
>    void perf_thread_map__set_pid(struct perf_thread_map *map, int thread, pid_t pid);
>    char *perf_thread_map__comm(struct perf_thread_map *map, int thread);
> diff --git a/tools/lib/perf/include/perf/threadmap.h b/tools/lib/perf/include/perf/threadmap.h
> index a7c50de8d010..47d433416040 100644
> --- a/tools/lib/perf/include/perf/threadmap.h
> +++ b/tools/lib/perf/include/perf/threadmap.h
> @@ -8,6 +8,7 @@
>  struct perf_thread_map;
>  
>  LIBPERF_API struct perf_thread_map *perf_thread_map__new_dummy(void);
> +LIBPERF_API struct perf_thread_map *perf_thread_map__new(int nr);
>  
>  LIBPERF_API void perf_thread_map__set_pid(struct perf_thread_map *map, int thread, pid_t pid);
>  LIBPERF_API char *perf_thread_map__comm(struct perf_thread_map *map, int thread);
> diff --git a/tools/lib/perf/libperf.map b/tools/lib/perf/libperf.map
> index 93696affda2e..240a2f087b70 100644
> --- a/tools/lib/perf/libperf.map
> +++ b/tools/lib/perf/libperf.map
> @@ -11,6 +11,7 @@ LIBPERF_0.0.1 {
>  		perf_cpu_map__empty;
>  		perf_cpu_map__max;
>  		perf_cpu_map__has;
> +		perf_thread_map__new;
>  		perf_thread_map__new_dummy;
>  		perf_thread_map__set_pid;
>  		perf_thread_map__comm;
> diff --git a/tools/lib/perf/tests/test-threadmap.c b/tools/lib/perf/tests/test-threadmap.c
> index 5e2a0291e94c..3388bf36dfc0 100644
> --- a/tools/lib/perf/tests/test-threadmap.c
> +++ b/tools/lib/perf/tests/test-threadmap.c
> @@ -11,9 +11,12 @@ static int libperf_print(enum libperf_print_level level,
>  	return vfprintf(stderr, fmt, ap);
>  }
>  
> +#define THREADS_NR	5
> +
>  int test_threadmap(int argc, char **argv)
>  {
>  	struct perf_thread_map *threads;
> +	int i;
>  
>  	__T_START;
>  
> @@ -27,6 +30,30 @@ int test_threadmap(int argc, char **argv)
>  	perf_thread_map__put(threads);
>  	perf_thread_map__put(threads);
>  
> +	threads = perf_thread_map__new(THREADS_NR);
> +	if (!threads)
> +		tests_failed++;
> +
> +	if (perf_thread_map__nr(threads) != THREADS_NR)
> +		tests_failed++;
> +
> +	for (i = 0; i < THREADS_NR; i++) {
> +		if (perf_thread_map__pid(threads, i) != -1)
> +			tests_failed++;
> +	}
> +
> +	for (i = 1; i < THREADS_NR; i++)
> +		perf_thread_map__set_pid(threads, i, i * 100);
> +
> +	if (perf_thread_map__pid(threads, 0) != -1)
> +		tests_failed++;
> +
> +	for (i = 1; i < THREADS_NR; i++) {
> +		if (perf_thread_map__pid(threads, i) != i * 100)
> +			tests_failed++;
> +	}
> +	perf_thread_map__put(threads);
> +
>  	__T_END;
>  	return tests_failed == 0 ? 0 : -1;
>  }
> diff --git a/tools/lib/perf/threadmap.c b/tools/lib/perf/threadmap.c
> index e92c368b0a6c..843fe1070cc9 100644
> --- a/tools/lib/perf/threadmap.c
> +++ b/tools/lib/perf/threadmap.c
> @@ -42,18 +42,25 @@ char *perf_thread_map__comm(struct perf_thread_map *map, int thread)
>  	return map->map[thread].comm;
>  }
>  
> -struct perf_thread_map *perf_thread_map__new_dummy(void)
> +struct perf_thread_map *perf_thread_map__new(int nr)
>  {
> -	struct perf_thread_map *threads = thread_map__alloc(1);
> +	struct perf_thread_map *threads = thread_map__alloc(nr);
> +	int i;
>  
>  	if (threads != NULL) {
> -		perf_thread_map__set_pid(threads, 0, -1);
> -		threads->nr = 1;
> +		for (i = 0; i < nr; i++)
> +			perf_thread_map__set_pid(threads, i, -1);
> +		threads->nr = nr;
>  		refcount_set(&threads->refcnt, 1);
>  	}
>  	return threads;
>  }
>  
> +struct perf_thread_map *perf_thread_map__new_dummy(void)
> +{
> +	return perf_thread_map__new(1);
> +}
> +
>  static void perf_thread_map__delete(struct perf_thread_map *threads)
>  {
>  	if (threads) {
> -- 
> 2.34.1
>