linux-kernel - Re: [PATCH [RT] 10/14] adjust pi

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Date:	Thu, 21 Feb 2008 11:48:51 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Gregory Haskins <ghaskins@...ell.com>
cc:	mingo@...e.hu, a.p.zijlstra@...llo.nl, tglx@...utronix.de,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	bill.huey@...il.com, kevin@...man.org, cminyard@...sta.com,
	dsingleton@...sta.com, dwalker@...sta.com, npiggin@...e.de,
	dsaxena@...xity.net, ak@...e.de, gregkh@...e.de,
	sdietrich@...ell.com, pmorreale@...ell.com, mkohari@...ell.com
Subject: Re: [PATCH [RT] 10/14] adjust pi_lock usage in wakeup


On Thu, 21 Feb 2008, Gregory Haskins wrote:

> From: Peter W.Morreale <pmorreale@...ell.com>
>
> In wakeup_next_waiter(), we take the pi_lock, and then find out whether
> we have another waiter to add to the pending owner.  We can reduce
> contention on the pi_lock for the pending owner if we first obtain the
> pointer to the next waiter outside of the pi_lock.
>
> This patch adds a measureable increase in throughput.

I see how this may decrease contention (slightly less time in holding the
pi_lock). But, please, when stating something like: "adds a measurable
increase in throughput", show the benchmark numbers.

-- Steve

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