linux-kernel - Re: [GIT PATCH] TTY patches for 2.6.33-git

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Message-ID: <20091213095534.58051536@infradead.org>
Date:	Sun, 13 Dec 2009 09:55:34 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <gregkh@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org
Subject: Re: [GIT PATCH] TTY patches for 2.6.33-git

On Sun, 13 Dec 2009 07:58:44 +0100
Ingo Molnar <mingo@...e.hu> wrote:

> 
> * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
> > We've had quite a bit of BKL work this merge-window. Maybe we'll
> > even get rid of it one of these days. There are "only" about 600
> > instances of "lock_kernel()" in the tree right now ;)
> 
> I tend to use unlock_kernel() as the metric. (as it's more precisely
> greppable and it is also more indicative of the underlying complexity
> of locking, as it gets used more in more complex scenarios)

another metric is... how many times do we take the BKL for some
workload. (For example booting or compiling a kernel).
A counter like "BKLs-per-second" would be nice to expose
(and then we can track that number going up as a regression etc)

For me, a secondary metric would be "how many times do we depend on the
magic auto-drop/reget behavior".. also easy to build a counter for.

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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