Em Tue, Jan 16, 2018 at 04:06:22PM +0100, Jiri Olsa escreveu:
> On Tue, Jan 16, 2018 at 08:40:38PM +0800, Cheng Jian wrote:
> > When i use perf to trace the sched_wakeup_new tracepoint, there is
> > a bug that output the same event repetitiously.
> > It can be reproduced by :
> >
> > #./test_fork
> > parent pid : 1059
> > child pid : 1060
> > #perf record -e sched:sched_wakeup_new -p 1060
> >
> > test_fork is an demo that can generating wakeup_new event, parent
> > process does nothing but fork a child process, and then they both
> > quit.
> >
> > There are 4 processors in this machine. before this patch,
> > perf script(perf-1058, parent-1059, child-1060) :
> >
> > test_fork 1059 [001] 62.913689: sched:sched_wakeup_new:
> > comm=test_fork pid=1060 prio=120 target_cpu=002
> > test_fork 1059 [001] 62.913698: sched:sched_wakeup_new:
> > comm=test_fork pid=1060 prio=120 target_cpu=002
> > test_fork 1059 [001] 62.913705: sched:sched_wakeup_new:
> > comm=test_fork pid=1060 prio=120 target_cpu=002
> >
> > but ftrace report this event only once :
> >
> > test_fork-1059 [002] d... 62.913680: sched_wakeup_new:
> > comm=test_fork pid=1060 prio=120 target_cpu=002
> >
> > perf script print the same wakeup_new event multiple times.
> >
> > These events which trigger this issue all specify a target process.
> > commit e6dab5ffab59 ("perf/trace: Add ability to set a target task
> > for events") has designed a method to trace these events. For
> > example, the sched_wakeup and sched_wakeup_new tracepoint will be
> > caught when the current task wakeup a target task.
> >
> > These events are registered as per cpu most of the time and attached
> > to the task too, we will get all of them from the perf_event_context
> > of this task, they will be matched success but are all the same event.
> > So check the cpu number of this event to avoid matching them multiple
> > times.
> >
> > after this patch, perf script(parent-1040, child-1041):
> >
> > test_fork 1040 [002] 36.536079: sched:sched_wakeup_new:
> > comm=test_fork pid=1041 prio=120 target_cpu=003
> >
> > It will match it only once for tracing task(child-1041).
> >
> > Signed-off-by: Cheng Jian <cj.chengj...@huawei.com>
>
> the duplicated events are gone.. solution looks ok to me
>
> Reviewed-and-Tested-by: Jiri Olsa <jo...@kernel.org>
I noticed that in the past as well, will try to test this too.
- Arnaldo
