linux-kernel - Re: [git pull] scheduler fixes

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Date:	Sun, 11 May 2008 16:32:27 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Sven Wegener <sven.wegener@...aler.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Alexander Viro <viro@....linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [git pull] scheduler fixes


* Matthew Wilcox <matthew@....cx> wrote:

> > the gain is rather obvious: two parallel up()s (or just up()s which 
> > come close enough after each other) will wake up two tasks in 
> > parallel. With your patch, the first guy wakes up and then it wakes 
> > up the second guy. I.e. your patch serializes the wakeup chain, mine 
> > keeps it parallel.
> 
> Yup.  I explained why that's actually beneficial in an earlier email.

but the problem is that by serializing the wakeup chains naively you 
introduced a more than 50% AIM7 performance regression.

	Ingo
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