[RFC PATCH 0/2] Implement get_user_pages_fast for ARM

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