[tip:perf/core] perf tools: fix broken perf record -a mode

tip-bot for Stephane Eranian
2012-02-22T16:04:31Z

Commit-ID: 6b1bee9035d430c4b4f586df6df4b3f840e89b5b
Gitweb: http://git.kernel.org/tip/6b1bee9035d430c4b4f586df6df4b3f840e89b5b
Author: Stephane Eranian <eranian@google.com>
AuthorDate: Tue, 21 Feb 2012 15:54:25 +0100
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 21 Feb 2012 15:05:43 -0200

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.

Acked-by: David Ahern <dsahern@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120221145424.GA6757@quad
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/thread_map.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

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;