Re: Impact of HIGHMEM?

From: Jens Axboe (
Date: Sat Dec 08 2001 - 15:05:29 EST

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 +, 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:

Jens Axboe

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