Messages in this thread | | | Date | Tue, 21 Feb 2012 08:31:56 -0700 | From | David Ahern <> | Subject | Re: [PATCH] perf tools: fix broken perf record -a mode |
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On 2/21/12 7:54 AM, Stephane Eranian wrote: > > 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;
Damn. Hope you did not spend much time chasing it down.
Acked-by: David Ahern <dsahern@gmail.com>
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