Re: [PATCH 3/5] mm, pagevec: Release/reacquire lru_lock on pgdat change

From: Johannes Weiner
Date: Mon Jul 18 2016 - 12:20:44 EST

On Fri, Jul 15, 2016 at 02:09:23PM +0100, Mel Gorman wrote:
> With node-lru, the locking is based on the pgdat. Previously it was
> required that a pagevec drain released one zone lru_lock and acquired
> another zone lru_lock on every zone change. Now, it's only necessary if
> the node changes. The end-result is fewer lock release/acquires if the
> pages are all on the same node but in different zones.
> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>

This could make quite a difference on some workloads, from a whole
series perspective, when considering that we had the round robin fair
zone allocator on top of this. Page batches that span multiple nodes
on the other hand are much less likely.

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>