linux-kernel - Re: [PATCH] oprofile: remove double ring buffering

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Message-ID: <20100320045902.GR20695@one.firstfloor.org>
Date:	Sat, 20 Mar 2010 05:59:02 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	robert.richter@....com
Subject: Re: [PATCH] oprofile: remove double ring buffering

On Sat, Mar 20, 2010 at 12:45:20AM -0400, Steven Rostedt wrote:
> On Sat, 2010-03-20 at 01:03 +0100, Andi Kleen wrote:
> > [This is currently being tested if it fixes the excessive samples
> > dropping I have been complaining about for some time. Still wanted
> > to post the patch for review.]
> > 
> > commit 49e66e8ab54f1114237e6dc24dc32ac912870c41
> > Author: Andi Kleen <ak@...ux.intel.com>
> > Date:   Fri Mar 19 21:03:48 2010 +0100
> > 
> >     oprofile: remove double ring buffering
> >     
> >     oprofile used a double buffer scheme for its cpu event buffer
> >     to avoid races on reading with the old lock less ring buffer.
> 
> The old ring buffer was not lockless, hence the need for two ring
> buffers because of NMIs. The new ring buffer is lockless.

Thanks. Description fixed.

-Andi
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