linux-kernel - Re: [BUG] perf sched broken

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Date:	Wed, 12 Jan 2011 11:10:39 -0800
From:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
To:	Arnaldo Carvalho de Melo <acme@...radead.org>
CC:	Stephane Eranian <eranian@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>, mingo@...e.hu,
	Robert Richter <robert.richter@....com>,
	Mike Galbraith <efault@....de>
Subject: Re: [BUG] perf sched broken

On 01/12/2011 04:11 AM, Arnaldo Carvalho de Melo wrote:
> Em Wed, Jan 12, 2011 at 10:29:05AM +0100, Stephane Eranian escreveu:
>> 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.
>
> I got to this point as well, and reverting 4c635a4 did the trick for me,
> Corey, this is another report for that problem, can you take a look at
> it? Stephane, can you try doing a:
>
> git show 4c635a4 | patch -p1 -R
>
> To see if the problem is fixed?
>

I will have a look at this now.  Thanks for the report.

- Corey

> - Arnaldo
>
>> $ 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?
>
> Good question, checking this s/trace/script/g fallout.
>
> - Arnaldo

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