Re: [lkp] [mm] 795ae7a0de: pixz.throughput -9.1% regression

[Mel Gorman <mgorman@suse.de>]

On Thu, Jun 02, 2016 at 12:07:06PM -0400, Johannes Weiner wrote:
> right before the test is running? I wonder if it's mostly filled with
> cache, and the increase in watermarks causes a higher portion of the
> anon allocs and frees to spill to the remote node, but never enough to
> enter the allocator slowpath and waking kswapd to fix it.
> 
> Another suspect is the fair zone allocator, whose allocation batches
> increased as well. It shouldn't affect NUMA placement, but I wonder if
> there is a bug in there that causes false spilling to foreign nodes
> that was only bounded by the allocation batch of the foreign zone.
> Mel, does such a symptom sound familiar in any way?
> 

Unfortunately not. The closest I've seen recently is bugs in the page
allocator patches that artifically enters the slow path prematurely but
that does not appear to apply here.

-- 
Mel Gorman
SUSE Labs