linux-kernel - Re: [PATCH 10/10 -v3][RFC] tracing: Combine event filter_active and enable into single flags field

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Date:	Tue, 11 May 2010 10:05:57 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH 10/10 -v3][RFC] tracing: Combine event filter_active
	and enable into single flags field

* Steven Rostedt (rostedt@...dmis.org) wrote:
> On Mon, 2010-05-10 at 23:30 -0400, Mathieu Desnoyers wrote:
> > * Steven Rostedt (rostedt@...dmis.org) wrote:
> > > From: Steven Rostedt <srostedt@...hat.com>
> > > 
> > > The filter_active and enable both use an int (4 bytes each) to
> > > set a single flag. We can save 4 bytes per event by combining the
> > > two into a single integer.
> > > 
> 
> > I would also comment about flags read-side:
> > 
> >  * Flags are read concurrently without locking.
> 
> That can go in outside this patch set. As we discussed before, the
> filter_active which does the same today as flags does here also has the
> issue you are concerned with. IOW, this issue has nothing to do with
> this patch set, because the issue existed before the patch set and has
> not changed after the patch set.

That's fine with me.

> 
> The comment should also be in Documentation, not here, since it would
> affect users more than the developers.

Typically, locking-related information belongs to comments close to the
definition. I'm not sure why you say it affects users at all.

Thanks,

Mathieu

> 
> > 
> > Besides that minor nit, the whole patchset has my
> > 
> > Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> 
> Thanks!  I'll get an official release ready.
> 
> -- Steve
> 
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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