Re: linux-linaro pull request

On Sat, Sep 18, 2010, Nicolas Pitre wrote:

Yet, highmem carries some small overhead of its own. So if you know that all the applications you need have a workset that always fits in a reduced address space then it is more advantageous to use a 2G:2G user:kernel split and keep highmem off.

Question: does highmem impact performance as soon as it's turned on, or only when actually using a lot of memory because the sliding window needs to move back and forth?

I'm asking because I would prefer if we were to have highmem turned on in all our kernels, even if not strictly required, as to have less divergence across SoCs, but I don't know whether there's a performance cost to it