From: Stephane Eranian Date: Tue, 21 Feb 2012 14:54:25 +0000 (+0100) Subject: perf tools: fix broken perf record -a mode X-Git-Tag: firefly_0821_release~3680^2~2798^3~79^2 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=6b1bee9035d430c4b4f586df6df4b3f840e89b5b;p=firefly-linux-kernel-4.4.55.git 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 Cc: David Ahern Cc: Eric Dumazet Cc: Ingo Molnar Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20120221145424.GA6757@quad Signed-off-by: Stephane Eranian Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/util/thread_map.c b/tools/perf/util/thread_map.c index e15983cf077d..84d9bd782004 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;