[ILUG] ftp.heanet.ie

[Paul Jakma]

On Mon, 12 Jan 2004 Conor_D_Wynne at Dell.com wrote:

> AFAIK You're fine until you go above 16GB [or hit 16GB that is]

Nope. First slowdown is once you install more than 1GB in an i386. 
After that, kernel can no longer be mapped into each processes 
address space and you take a vm context swap on each transition 
between kernel and process vm context (interrupts/system calls).

The next slow down is > 4GB, then you're using PAE which introduces 
an additional level of indirection in page tables. And IO to/from 
data located above 4GB physical has to be bounce buffered.

Now, 2.4 appears to have a CONFIG_HIGHIO which says:

"If you want to be able to do I/O to high memory pages, say Y. 
Otherwise low memory pages are used as bounce buffers causing a 
degrade in performance."

But I see little reference to it, and I cant think how it would work 
on i386. anyone know?

regards,
-- 
Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
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