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    Subject[PATCH] perf tools: fix broken perf record -a mode

    The following commit:
    b52956c perf tools: Allow multiple threads or processes in record, stat, top

    introduced a bug in the thread_map code which caused
    perf record -a to not setup system-wide monitoring properly.

    $ taskset -c 1 noploop 1000 &
    $ perf record -a -C 1 sleep 10
    $ perf report -D | tail -20
    cycles stats:
    TOTAL events: 4413
    MMAP events: 4025
    COMM events: 340
    SAMPLE events: 48

    Here I was expecting about 10,000 samples and not 48.

    In system-wide mode, the PID passed to perf_event_open()
    must be -1 and it was 0. That caused the kernel to setup
    a per-process event on PID:0. Consequently, the number
    of samples captured does not correspond to the requested
    measurement.

    The following one-liner fixes the problem for me with or
    without -C.

    I would also suggest to change the malloc() to something
    that matches the struct definition. thread_map->map[] is
    declared as int map[] and not pid_t map[]. If map[] can
    only contain pids, then change the struct definition.

    Signed-off-by: Stephane Eranian <eranian@google.com>
    ---

    diff --git a/tools/perf/util/thread_map.c b/tools/perf/util/thread_map.c
    index e15983c..84d9bd78 100644
    --- a/tools/perf/util/thread_map.c
    +++ b/tools/perf/util/thread_map.c
    @@ -229,7 +229,7 @@ static struct thread_map *thread_map__new_by_tid_str(const char *tid_str)
    if (!tid_str) {
    threads = malloc(sizeof(*threads) + sizeof(pid_t));
    if (threads != NULL) {
    - threads->map[1] = -1;
    + threads->map[0] = -1;
    threads->nr = 1;
    }
    return threads;

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