linux-kernel - Re: [PATCH 2/3] ring-buffer: make lockless

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Message-ID: <alpine.DEB.2.00.0907081711200.22197@gandalf.stny.rr.com>
Date:	Wed, 8 Jul 2009 17:16:59 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Mathieu Desnoyers <compudj@...stal.dyndns.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>,
	Steven Rostedt <srostedt@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH 2/3] ring-buffer: make lockless


On Wed, 8 Jul 2009, Mathieu Desnoyers wrote:

> * Steven Rostedt (rostedt@...dmis.org) wrote:
> > From: Steven Rostedt <srostedt@...hat.com>
> > 
> > This patch converts the ring buffers into a completely lockless
> > buffer recording system. The read side still takes locks since
> > we still serialize readers. But the writers are the ones that
> > must be lockless (those can happen in NMIs).
> 
> Hi Steven,
> 
> Have you started modeling this scheme with Promela as I previously
> discussed with you ? Paul McKenney did a lot of nice papers on the
> topic, and given the complexity level of this lockless buffering
> algorithm, I'd be much more comfortable if it was formally verified. The
> idea here is to make sure we don't start an endless bug-chasing hunt as
> trace buffers gets more exposure to various workloads.

I would when I get time. Too many things on my plate at the moment. But 
I do constantly run my ring-buffer-benchmark module, which highly stresses 
the buffer. I have not had to fix a bug in it for a long time, and nothing 
that needed a design change.

I'll try it out (or better yet, maybe someone else will) when I get more 
time.

-- Steve

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