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Date: Tue, 13 May 2008 16:11:29 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Matthew Wilcox <matthew@wil.cx>
Cc: Sven Wegener <sven.wegener@stealer.net>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
       Andi Kleen <andi@firstfloor.org>, LKML <linux-kernel@vger.kernel.org>,
       Alexander Viro <viro@ftp.linux.org.uk>,
       Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [git pull] scheduler fixes
Message-ID: <20080513141129.GC18798@elte.hu>
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* Matthew Wilcox <matthew@wil.cx> wrote:

> > So why not transform it to real completions instead? And if our 
> > current 'struct completion' abstraction is insufficient for whatever 
> > reason, why not extend that instead?
> 
> My point is that for the only user of counting semaphores and/or 
> semaphores-abused-as-completions that has so far hit this race, the 
> serialised wake-up performs better.  You have not pointed at a 
> scenario that _shows_ a parallel wake-up to perform better. [...]

a 50% AIM7 slowdown maybe? With the BKL being a spinlock again it doesnt 
matter much in practice though.

	Ingo