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Date: Sat, 12 Jan 2002 12:36:04 -0700
From: yodaiken@fsmlabs.com
To: Robert Love <rml@tech9.net>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, arjan@fenrus.demon.nl,
        Rob Landley <landley@trommello.org>, linux-kernel@vger.kernel.org
Subject: Re: [2.4.17/18pre] VM and swap - it's really unusable
Message-ID: <20020112123604.C6034@hq.fsmlabs.com>
In-Reply-To: <E16PTIR-0002sL-00@the-village.bc.nu> <1010863588.2007.34.camel@phantasy>
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In-Reply-To: <1010863588.2007.34.camel@phantasy>; from rml@tech9.net on Sat, Jan 12, 2002 at 02:26:27PM -0500
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On Sat, Jan 12, 2002 at 02:26:27PM -0500, Robert Love wrote:
> On Sat, 2002-01-12 at 13:54, Alan Cox wrote:
> > Another example is in the network drivers. The 8390 core for one example
> > carefully disables an IRQ on the card so that it can avoid spinlocking on 
> > uniprocessor boxes.
> > 
> > So with pre-empt this happens
> > 
> > 	driver magic
> > 	disable_irq(dev->irq)
> > PRE-EMPT:
> > 	[large periods of time running other code]
> > PRE-EMPT:
> > 	We get back and we've missed 300 packets, the serial port sharing
> > 	the IRQ has dropped our internet connection completely.
> 
> We don't preempt while IRQ are disabled.

You read the mask map? and somehow figure out which masked irqs correspond to 
active devices?

> 
> 	Robert Love
> 
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-- 
---------------------------------------------------------
Victor Yodaiken 
Finite State Machine Labs: The RTLinux Company.
 www.fsmlabs.com  www.rtlinux.com

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