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From: Alan <alan@lxorguk.ukuu.org.uk>
To: Zachary Amsden <zach@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
	Pavel Machek <pavel@ucw.cz>, 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 00:33:39 +0000	[thread overview]
Message-ID: <20070215003339.1420faff@localhost.localdomain> (raw)
In-Reply-To: <45D384C4.2000306@vmware.com>

On Wed, 14 Feb 2007 13:53:08 -0800
Zachary Amsden <zach@vmware.com> wrote:

> > IDE on several platforms has performance critical paths that use
> > ndelay(400) or failing that udelay(1)
> 
> Ok, I buy that.  A 486DX / 33 Mhz processor takes 10 cycles to issue a 
> CALL / RET pair.  This is about 300ns.  Is there an issue with being too 
> early to issue I/O operations or too late?

Too early you lose, too late you just waste clock time.

> But I fail to see how such careful timing can be done at this 
> granularity on such hardware without well tweaked assembly code. 

Thats what is used  most platforms use udelay(1) in fact however

  reply	other threads:[~2007-02-14 23:31 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 [this message]
2007-02-15 10:17             ` Pavel Machek
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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