linux-kernel - Re: [REPORT] cfs-v4 vs sd-0.44

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Message-ID: <alpine.LFD.0.98.0704211634130.9964@woody.linux-foundation.org>
Date:	Sat, 21 Apr 2007 16:35:33 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ulrich Drepper <drepper@...il.com>
cc:	Kyle Moffett <mrmacman_g4@....com>,
	William Lee Irwin III <wli@...omorphy.com>,
	Willy Tarreau <w@....eu>, Ingo Molnar <mingo@...e.hu>,
	Con Kolivas <kernel@...ivas.org>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>, Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Peter Williams <pwil3058@...pond.net.au>,
	Thomas Gleixner <tglx@...utronix.de>, caglar@...dus.org.tr,
	Gene Heskett <gene.heskett@...il.com>
Subject: Re: [REPORT] cfs-v4 vs sd-0.44



On Sat, 21 Apr 2007, Ulrich Drepper wrote:
> 
> If you do this, and it has been requested many a times, then please
> generalize it.  We have the same issue with futexes.  If a FUTEX_WAIT
> call is issues the remaining time in the slot should be given to the
> thread currently owning the futex.

And how the hell do you imagine you'd even *know* what thread holds the 
futex?

The whole point of the "f" part of the mutex is that it's fast, and we 
never see the non-contended case in the kernel. 

So we know who *blocks*, but we don't know who actually didn't block.

		Linus
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