Re: [LKP] [lkp] [xfs] 68a9f5e700: aim7.jobs-per-min -13.6% regression

Michal Hocko
2016-08-17T16:43:00Z

On Wed 17-08-16 17:48:25, Michal Hocko wrote:
[...]
> I will try to catch up with the rest of the email thread but from a
> quick glance it just feels like we are doing more more work under the
> lock.

Hmm, so it doesn't seem to be more work in __remove_mapping as pointed
out in http://lkml.kernel.org/r/20160816220250.GI16044@dastard

As Mel already pointed out the LRU will be basically single mapping for
this workload so any subtle change in timing might make a difference.
I was looking through 4.6..4.7 and one thing that has changed is the
inactive vs. active LRU size ratio. See 59dc76b0d4df ("mm: vmscan:
reduce size of inactive file list"). The machine has quite a lot of
memory and so the LRUs will be large as well so I guess this could have
change the timing somehow, but it feels like a wild guess so I would be
careful to blame this commit...
--
Michal Hocko
SUSE Labs