linux-kernel - Re: [PATCH 1/7] ring-buffer: remove unneeded conditional in rb_reserve

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Message-ID: <20090507082303.GE12285@elte.hu>
Date:	Thu, 7 May 2009 10:23:03 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Li Zefan <lizf@...fujitsu.com>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH 1/7] ring-buffer: remove unneeded conditional in
	rb_reserve_next


* Steven Rostedt <rostedt@...dmis.org> wrote:

> From: Steven Rostedt <srostedt@...hat.com>
> 
> The code in __rb_reserve_next checks on page overflow if it is the
> original commiter and then resets the page back to the original
> setting.  Although this is fine, and the code is correct, it is
> a bit fragil. Some experimental work I did breaks it easily.

s/fragil/fragile

> The better and more robust solution is to have all commiters that
> overflow the page, simply subtract what they added.
> 
> [ Impact: more robust ring buffer account management ]

it's a bit faster too (eliminates two branches) - so a 
micro-optimization as well.

	Ingo
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