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Subject: Re: Dmesg: Use a PAE enabled kernel
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Andrew Walrond <andrew@walrond.org>
Cc: "Martin J. Bligh" <mbligh@aracnet.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Mon, 2003-03-03 at 16:49, Andrew Walrond wrote:
> That accounts for the missing Gb then. I think the warning needs to be 
> more like "WARNING WARNING (WILL ROBINSON)! 1GB of very expensive ram 
> won't be used unless you enable PAE!!!"

That would require we could detect rambus memory 8)

	printk("Warning %dGb of %sram won't be used.\n", lost>>10,
rambus()?"expensive ");

But yes more seriously it would be a lot more useful and more
meaningful to tell people how much ram is not being used

> Just how slow is PAE then ?

It varies, it can cost you 5-10%. The bigger hit is that most 
I/O devices can't reach that memory directly from PCI space
so you get bounce buffer costs and more paging/vm management
overhead.


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