[RFC PATCH 0/2] Implement get_user_pages_fast for ARM

[Will Deacon]

On Fri, Oct 18, 2013 at 02:07:11PM +0100, Steve Capper wrote:
> This patch series implements get_user_pages_fast on ARM. Unlike other
> architectures, we do not use IPIs/disabled IRQs as a blocking
> mechanism to protect the page table walker. Instead an atomic counter
> is used to indicate how many fast gup walkers are active on an address
> space, and any code that would cause them problems (THP splitting or
> code that could free a page table page) spins on positive values of
> this counter.

Curious: did you try benchmarking the two schemes? Whilst I expect this
algorithm to be better on ARM, exclusive memory accesses aren't free and
we're adding code to the fast path.

Will