linux-kernel - Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3

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Message-ID: <20070223102253.GA22870@elte.hu>
Date:	Fri, 23 Feb 2007 11:22:53 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Michael K. Edwards" <medwards.linux@...il.com>
Cc:	Alan <alan@...rguk.ukuu.org.uk>,
	Evgeniy Polyakov <johnpol@....mipt.ru>,
	Ulrich Drepper <drepper@...hat.com>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@....com.au>,
	Zach Brown <zach.brown@...cle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3


* Michael K. Edwards <medwards.linux@...il.com> wrote:

> On 2/22/07, Alan <alan@...rguk.ukuu.org.uk> wrote:

> > We don't use the FPU in the kernel except in very weird cases where 
> > it makes an enormous performance difference. The threadlets also 
> > have the same page tables so they have the same %cr3 so its very 
> > cheap to switch, basically a predicted jump and some register loads
> 
> Do you not understand that real user code touches FPU state at 
> unpredictable (to the kernel) junctures?  Maybe not in a database or a 
> web server, but in the GUIs and web-based monitoring applications that 
> are 99% of the potential customers for kernel AIO?
> I have no idea what a %cr3 is, [...]

then please stop wasting Alan's time ...

	Ingo
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