linux-kernel - Re: [PATCH 00/14] [GIT PULL][v2.6.39] tracing/filter: More robust filtering

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Date:	Wed, 16 Feb 2011 22:34:07 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Tom Zanussi <tzanussi@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	2nddept-manager@....hitachi.co.jp
Subject: Re: [PATCH 00/14] [GIT PULL][v2.6.39] tracing/filter: More robust
 filtering

(2011/02/16 3:35), Arnaldo Carvalho de Melo wrote:
> Em Tue, Feb 15, 2011 at 05:53:06PM +0100, Frederic Weisbecker escreveu:
>> On Tue, Feb 15, 2011 at 11:29:22AM -0500, Steven Rostedt wrote:
>>> On Tue, 2011-02-15 at 08:33 -0500, Steven Rostedt wrote:
>>>
>>>> Thanks for letting me waste three days on developing this. I even posted
>>>> an RFC a while back, and no one complained then.
>>>
>>> Sorry about being a bit bitchy in my reply here. I need to make a note
>>> not to reply to LKML before my first cup of coffee. ;)
>>>
>>> Arnaldo,
>>>
>>> Thanks for the post, I'll help you out where you need it. trace-cmd has
>>> some features that reports back to the user on failed filter usage. We
>>> can incorporate that into perf.
> 
> Thanks!

Sounds good :)

>  
>> Cool!
>>
>> That said I agree that we should not block improvements in the generic
>> filtering code because of issues in perf uses of filters.
>>
>> I believe it used to work better in perf by the past, but I saw similar
>> issues lately like those Ingo noticed. So probably something
>> broke and we need to investigate. But until then your patches are
>> still nice improvements: lesser memory usage, lesser kernel stack usage in the
>> fast path, lesser limitation, faster and smarter filter evaluation...
> 
> Yeah, usability of the --filter parameter in perf is a bit
> (understatement) lacking, one has to look at the /format thing in
> /sys/kernel/debug/tracing... and not commit any mistake, else a generic
> invalid 22 message is spit out.

And also, there seems very less comment in perf-record.txt.

--filter=<filter>::
        Event filter.

Hmm, I think, at least, there should be a comment where user should
refer to and if possible, how he can use it...


> I tried it and after some back and forth changing hats and scratching my
> head while doing so, it got to work.
> 
> I talked with Steven and the same operation using trace-cmd would
> produce a better error report, stating that the field used in the filter
> expression was not valid.

If possible, please show us what parameters we can use on that event too.
perf list gives us a list of events, but not show us what parameters
we can use on those events. I think we can update perf list for that
purpose.

e.g.)
perf list --field kvm:kvm_entry
 unsigned short common_type;
 unsigned char common_flags;
 unsigned char common_preempt_count;
 int common_pid;
 int common_lock_depth;
 unsigned int vcpu_id;


> 
> I'll try to get that code from trace-cmd and glue that into
> tools/perf/util/, that eventually will get moved to tools/lib/ or
> something like that, as Borislav has been experimenting with for some
> time already.
> 
> The location in the source tree is not the most important thing at this
> point, usability improvements are, so I'm not rushing to moving code
> around all the time (even doing it more than I would like), lets try to
> improve usability first and then we can move it to tools/lib.
> 
> - Arnaldo


Thank you,

-- 
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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