Re: [PATCH v2] libperf: Add API for allocating new thread map

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Feb 21, 2022 at 12:26:28PM +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_array()
> 
> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
> ---
> v2 changes:
>  - Changed the new API as Arnaldo suggested - get number of threads in the
>    map and array with initial values (optional).

looks good, would you also find useful in your use case the comm support
in thread_map? the thread_map__read_comms function? we could move it from
perf to libperf

thanks,
jirka

> 
>  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    | 41 ++++++++++++++++++++++++
>  tools/lib/perf/threadmap.c               | 24 ++++++++++----
>  5 files changed, 61 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/lib/perf/Documentation/libperf.txt b/tools/lib/perf/Documentation/libperf.txt
> index a21f733b95b1..a8f1a237931b 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_array(int nr_threads, pid_t *array);
>  
>    void perf_thread_map__set_pid(struct perf_thread_map *map, int idx, pid_t pid);
>    char *perf_thread_map__comm(struct perf_thread_map *map, int idx);
> diff --git a/tools/lib/perf/include/perf/threadmap.h b/tools/lib/perf/include/perf/threadmap.h
> index 58f7fbdce446..8b40e7777cea 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_array(int nr_threads, pid_t *array);
>  
>  LIBPERF_API void perf_thread_map__set_pid(struct perf_thread_map *map, int idx, pid_t pid);
>  LIBPERF_API char *perf_thread_map__comm(struct perf_thread_map *map, int idx);
> diff --git a/tools/lib/perf/libperf.map b/tools/lib/perf/libperf.map
> index 6fa0d651576b..190b56ae923a 100644
> --- a/tools/lib/perf/libperf.map
> +++ b/tools/lib/perf/libperf.map
> @@ -12,6 +12,7 @@ LIBPERF_0.0.1 {
>  		perf_cpu_map__empty;
>  		perf_cpu_map__max;
>  		perf_cpu_map__has;
> +		perf_thread_map__new_array;
>  		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..f728ad7002bb 100644
> --- a/tools/lib/perf/tests/test-threadmap.c
> +++ b/tools/lib/perf/tests/test-threadmap.c
> @@ -11,9 +11,43 @@ static int libperf_print(enum libperf_print_level level,
>  	return vfprintf(stderr, fmt, ap);
>  }
>  
> +static int test_threadmap_array(int nr, pid_t *array)
> +{
> +	struct perf_thread_map *threads;
> +	int i;
> +
> +	threads = perf_thread_map__new_array(nr, array);
> +	__T("Failed to allocate new thread map", threads);
> +
> +	__T("Unexpected number of threads", perf_thread_map__nr(threads) == nr);
> +
> +	for (i = 0; i < nr; i++) {
> +		__T("Unexpected initial value of thread",
> +		    perf_thread_map__pid(threads, i) == (array ? array[i] : -1));
> +	}
> +
> +	for (i = 1; i < nr; i++)
> +		perf_thread_map__set_pid(threads, i, i * 100);
> +
> +	__T("Unexpected value of thread 0",
> +	    perf_thread_map__pid(threads, 0) == (array ? array[0] : -1));
> +
> +	for (i = 1; i < nr; i++) {
> +		__T("Unexpected thread value",
> +		    perf_thread_map__pid(threads, i) == i * 100);
> +	}
> +
> +	perf_thread_map__put(threads);
> +
> +	return 0;
> +}
> +
> +#define THREADS_NR	10
>  int test_threadmap(int argc, char **argv)
>  {
>  	struct perf_thread_map *threads;
> +	pid_t thr_array[THREADS_NR];
> +	int i;
>  
>  	__T_START;
>  
> @@ -27,6 +61,13 @@ int test_threadmap(int argc, char **argv)
>  	perf_thread_map__put(threads);
>  	perf_thread_map__put(threads);
>  
> +	test_threadmap_array(THREADS_NR, NULL);
> +
> +	for (i = 0; i < THREADS_NR; i++)
> +		thr_array[i] = i + 100;
> +
> +	test_threadmap_array(THREADS_NR, thr_array);
> +
>  	__T_END;
>  	return tests_failed == 0 ? 0 : -1;
>  }
> diff --git a/tools/lib/perf/threadmap.c b/tools/lib/perf/threadmap.c
> index 84fa07c79d00..07968f3ea093 100644
> --- a/tools/lib/perf/threadmap.c
> +++ b/tools/lib/perf/threadmap.c
> @@ -42,18 +42,28 @@ char *perf_thread_map__comm(struct perf_thread_map *map, int idx)
>  	return map->map[idx].comm;
>  }
>  
> -struct perf_thread_map *perf_thread_map__new_dummy(void)
> +struct perf_thread_map *perf_thread_map__new_array(int nr_threads, pid_t *array)
>  {
> -	struct perf_thread_map *threads = thread_map__alloc(1);
> +	struct perf_thread_map *threads = thread_map__alloc(nr_threads);
> +	int i;
> +
> +	if (!threads)
> +		return NULL;
> +
> +	for (i = 0; i < nr_threads; i++)
> +		perf_thread_map__set_pid(threads, i, array ? array[i] : -1);
> +
> +	threads->nr = nr_threads;
> +	refcount_set(&threads->refcnt, 1);
>  
> -	if (threads != NULL) {
> -		perf_thread_map__set_pid(threads, 0, -1);
> -		threads->nr = 1;
> -		refcount_set(&threads->refcnt, 1);
> -	}
>  	return threads;
>  }
>  
> +struct perf_thread_map *perf_thread_map__new_dummy(void)
> +{
> +	return perf_thread_map__new_array(1, NULL);
> +}
> +
>  static void perf_thread_map__delete(struct perf_thread_map *threads)
>  {
>  	if (threads) {
> -- 
> 2.34.1
>