linux-kernel - Re: [PATCH 27/30] workqueue: implement DEBUGFS/workqueue

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Message-ID: <4C17AD76.2010707@kernel.org>
Date:	Tue, 15 Jun 2010 18:42:30 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	mingo@...e.hu, awalls@...ix.net, linux-kernel@...r.kernel.org,
	jeff@...zik.org, akpm@...ux-foundation.org, rusty@...tcorp.com.au,
	cl@...ux-foundation.org, dhowells@...hat.com,
	arjan@...ux.intel.com, johannes@...solutions.net, oleg@...hat.com,
	axboe@...nel.dk, Anton Blanchard <anton@...ba.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 27/30] workqueue: implement DEBUGFS/workqueue

Hello,

On 06/15/2010 03:54 PM, Frederic Weisbecker wrote:
> I don't like this. This adds 300 lines of ad hoc in-kernel
> instrumentation code while we now have a nice kernel tracing API
> (trace events) coupled with easy userspace tools to post-process
> that (perf trace scripting). And this is going to provide a much
> more powerful view of your new workqueue implementation runtime
> behaviour.
>
> We already have kernel/trace/trace_workqueue.c that has been
> obsolated for these very reasons and we are even going to remove it
> soon, probably for .36
>
> Please work with us for that, if everybody makes his own corner
> instrumentation, we are not going to make any progress in having a
> powerful and unified tracing/profiling.
>
> The first step is to pinpoint the important places that need
> tracepoints, and then just write a perf trace script to use the
> provided informations by these tracepoints.
> 
> I can help about that if needed.

Yeah, I agree that trace would be better way to do it.  This patch was
added because slow-work had similar facility and David was unhappy
about losing easy way to monitor if cmwq replaces slow-work.  I'll be
happy to drop this one.  David, what do you think?

Thanks.

-- 
tejun
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