Re: Hardwired drivers are going away?

Andi Kleen
2002-01-15T12:16:21Z

peter@horizon.com writes:

> 1) The main kernel is contiguous in physical memory and is mapped with
> large (4 MB) pages. This reduces pressure on the TLB. Modules are
> loaded in vmalloc memory, which uses small pages, and therefore
> competes for TLB space. This is a performance penalty, especially
> as most current machines have undersized TLBs already. (A 64-entry
> TLB with 4K pages maps 256K at a time. On-chip L2 caches are this
> large or larger. Thus, as a crude approximation, every L2 miss also
> causes a TLB miss.)

-aa tries to load modules into the linear mapping when possible.
That usually works when you load the modules early when the memory
isn't that fragmented yet.

I agree on that trying to put everything into modules isn't a good idea,
especially because of your second point.

-Andi