Messages in this thread | | | Date | Tue, 21 Feb 2012 15:07:54 -0200 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH] perf tools: fix broken perf record -a mode |
| |
Em Tue, Feb 21, 2012 at 08:31:56AM -0700, David Ahern escreveu: > 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.
Stephane,
Feel free to submit a patch :-)
>> 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>
Yeah, this one slip thru my visual inspection :-\
Now I'll pay for this sin by adding an entry in 'perf test' to check that :-)
- Arnaldo
| |