Re: Impact of HIGHMEM?

Jens Axboe (axboe@suse.de)
Sat, 8 Dec 2001 21:05:29 +0100

On Sat, Dec 08 2001, Ivanovich wrote:
> A Dissabte 08 Desembre 2001 20:03, war va escriure:
> > Does anyone have any benchmarks as to how much HIGHMEM affects
> > performance in Linux?
> >
> > Searched google.com + groups.google.com, couldn't find anything solid
> > though.
>
> why don't you try to compile a kernel with HIGHMEM and another without it and
> then run some benchmarks in each one and compare?

You'll very quickly spend a significant amount of sys time copying pages
back and forth.

> not everyone have the amount of ram to test this (i only have
> 256...(sigh)) if i had that amount i would run some bench...

You don't need lots of mem to test highmem impact, just grab the highmem
debug patch from Andrea:

kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.17pre4aa1/20_highmem-debug-7

-- 
Jens Axboe


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