Re: [BUG] perf sched broken

Corey Ashford
2011-01-13T01:54:08Z

On 01/12/2011 01:29 AM, Stephane Eranian wrote:
> Hi,
>
> I am trying to use perf sched from tip-x86 but it fails for all my attempts.
>
> First of, I think the event list is stale. This is not so much the
> events themselves
> but rather the flags.
>
> Looks to me like the :r modifier is not supported anymore, so a patch like the
> one below is needed. That helps collect a trace. But then, you can dump
> the trace.

After looking at this in more detail, I agree with Stephane: the 'r'
option appears to only be supported for hardware breakpoint events. My
patch just causes the 'r' to be properly processed and rejected as a
legal option.

As I stated elsewhere in this thread, I don't have a problem running the
perf commands below on a Fedora 14, 2.6.35 kernel, using the perf from
2.6-tip master or x86/urgent.

I don't have a 2.6.37-tip kernel installed at the moment, but if you
still think this could be a perf tool bug that occurs only when using it
with a 2.6.37-tip kernel, let me know and I will devote some time to
trying it out.

- Corey

>
> $ perf sched rec dd if=/dev/zero of=/dev/null count=1000000
> 1000000+0 records in
> 1000000+0 records out
> 512000000 bytes (512 MB) copied, 0.589981 s, 868 MB/s
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.481 MB perf.data (~20997 samples) ]
>
> $ perf sched rep
> run measurement overhead: 2934 nsecs
> sleep measurement overhead: 90502 nsecs
> the run test took 999149 nsecs
> the sleep test took 1092248 nsecs
> Fatal: no trace data in the file
>
> $ perf sched trace -D
> usage: perf sched [<options>] {record|latency|map|replay|trace}
>
> -i, --input<file> input file name
> -v, --verbose be more verbose (show symbol address, etc)
> -D, --dump-raw-trace dump raw trace in ASCII
>
> Note that this is not specific to pref sched. If I use perf record directly,
> I run into the same issue:
> $ perf record -R -a -c 1 -e sched:sched_switch -- sleep 1
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.365 MB perf.data (~15962 samples) ]
> $./perf report -D
> Fatal: no trace data in the file
>
> Now that perf trace is gone, how to I dump the trace?
>
>
> Drop :r modifier for tracepoints
>
> Signed-off-by: Stephane Eranian<eranian@google.com>
> ---
>
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index abd4b84..29e7ffd 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -1843,15 +1843,15 @@ static const char *record_args[] = {
> "-f",
> "-m", "1024",
> "-c", "1",
> - "-e", "sched:sched_switch:r",
> - "-e", "sched:sched_stat_wait:r",
> - "-e", "sched:sched_stat_sleep:r",
> - "-e", "sched:sched_stat_iowait:r",
> - "-e", "sched:sched_stat_runtime:r",
> - "-e", "sched:sched_process_exit:r",
> - "-e", "sched:sched_process_fork:r",
> - "-e", "sched:sched_wakeup:r",
> - "-e", "sched:sched_migrate_task:r",
> + "-e", "sched:sched_switch",
> + "-e", "sched:sched_stat_wait",
> + "-e", "sched:sched_stat_sleep",
> + "-e", "sched:sched_stat_iowait",
> + "-e", "sched:sched_stat_runtime",
> + "-e", "sched:sched_process_exit",
> + "-e", "sched:sched_process_fork",
> + "-e", "sched:sched_wakeup",
> + "-e", "sched:sched_migrate_task",
> };
> --
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