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From: Pavel Machek <pavel@ucw.cz>
To: Zachary Amsden <zach@vmware.com>
Cc: Alan <alan@lxorguk.ukuu.org.uk>,
	Rusty Russell <rusty@rustcorp.com.au>, Andi Kleen <ak@muc.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@osdl.org>,
	Jeremy Fitzhardinge <jeremy@goop.org>,
	Chris Wright <chrisw@sous-sol.org>
Subject: Re: [PATCH 9/11] Panic delay fix
Date: Thu, 15 Feb 2007 11:17:13 +0100	[thread overview]
Message-ID: <20070215101713.GK26240@elf.ucw.cz> (raw)
In-Reply-To: <45D36B49.5090109@vmware.com>

Hi!

> >>We'd have to audit and figure out what udelays are for hardware and
> >>which are not, but the evidence is that the vast majority of them are
> >>for hardware and not needed for virtualization.
> >>    
> >
> >Which is irrelevant since the hardware drivers won't be used in a
> >virtualised environment with any kind of performance optimisation.
> >  
> 
> Which is why an audit is irrelevant for the most part.  Note on the 
> performance below.

You know it is ugly. Alan demonstrated it even hurts performance, but
being ugly is the main problem.

If you _need_ to avoid udelay() in some cases, introduce
udelay_unless_virtualized(), and switch few users to it. Just globaly
defining udelay to nop is _ugly_.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

  parent reply	other threads:[~2007-02-15 10:17 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-06  3:53 Zachary Amsden
2007-02-06 12:27 ` Andi Kleen
2007-02-06 21:59   ` Zachary Amsden
2007-02-07 12:35     ` Pavel Machek
2007-02-07 20:36       ` Rusty Russell
2007-02-07 22:23         ` Zachary Amsden
2007-02-08 14:43         ` Dmitry Torokhov
2007-02-08 21:26           ` Zachary Amsden
2007-02-08 21:37             ` Dmitry Torokhov
2007-02-14 12:26         ` Pavel Machek
2007-02-14 19:47           ` Zachary Amsden
2007-02-14 12:52         ` Alan
2007-02-14 20:04           ` Zachary Amsden
2007-02-14 21:34             ` Alan
2007-02-14 21:53               ` Zachary Amsden
2007-02-15  0:33                 ` Alan
2007-02-15 10:17             ` Pavel Machek [this message]
2007-02-15 23:42               ` Zachary Amsden
2007-02-15 23:49                 ` Pavel Machek
2007-02-15 23:50                 ` Jeremy Fitzhardinge
2007-02-16  3:22                 ` Rusty Russell
2007-02-07 14:58     ` Dmitry Torokhov
2007-02-07 22:31       ` Zachary Amsden
2007-02-08  8:24         ` Andi Kleen
2007-02-08  9:08           ` Zachary Amsden
2007-02-08 13:33             ` Andi Kleen
2007-02-08 14:41               ` Dmitry Torokhov
2007-02-14 12:49             ` Alan
2007-02-14 22:51 ` Rusty Russell
2007-02-15  0:28   ` Alan
2007-02-15 13:35   ` Dmitry Torokhov

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