Re: Dmesg: Use a PAE enabled kernel

Alan Cox (
03 Mar 2003 19:22:42 +0000

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

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