[Andi Kleen <ak@linux.intel.com>]

Dave Chinner <david@fromorbit.com> writes:

> Thoughts, comments, etc?

The interesting part is if it will cause additional tail latencies
allocating under fragmentation with direct reclaim, compaction
etc. being triggered before it falls back to the base page path.

In fact it is highly likely it will, the question is just how bad it is.

Unfortunately benchmarking for that isn't that easy, it needs artificial
memory fragmentation and then some high stress workload, and then
instrumenting the transactions for individual latencies. 

I would in any case add a tunable for it in case people run into this.
Tail latencies are a common concern on many IO workloads.

-Andi