Re: [PATCH 00/27] Move LRU page reclaim from zones to nodes v7

[Mel Gorman]

On Thu, Jun 23, 2016 at 01:27:14PM +0200, Michal Hocko wrote:
> On Thu 23-06-16 11:26:48, Mel Gorman wrote:
> > On Tue, Jun 21, 2016 at 03:15:39PM +0100, Mel Gorman wrote:
> > > The bulk of the updates are in response to review from Vlastimil Babka
> > > and received a lot more testing than v6.
> > > 
> > 
> > Hi Andrew,
> > 
> > Please drop these patches again from mmotm.
> > 
> > There has been a number of odd conflicts resulting in at least one major
> > bug where a node-counter is used on a zone that will result in random
> > behaviour. Some of the additional feedback is non-trivial and all of it
> > will need to be resolved against the OOM detection rework and the huge
> > tmpfs implementation.
> 
> FWIW I haven't spotted any obvious misbehaving wrt. the OOM detection
> rework. You have kept the per-zone counters which are used for the retry
> logic so I think we should be safe. I am still reading through the
> series though.
> 

The main snag is NR_FILE_DIRTY and NR_WRITEBACK in should_reclaim_retry.
It currently is a random number generator if it reads a zone stat
instead of the node one. In some configurations, it even reads values
after the stats array.

-- 
Mel Gorman
SUSE Labs