Re: [PATCH 0/3] OOM detection rework v4

[Joonsoo Kim]

On Tue, Mar 01, 2016 at 02:38:46PM +0100, Michal Hocko wrote:
> > I'd expect a build in 224M
> > RAM plus 2G of swap to take so long, that I'd be very grateful to be
> > OOM killed, even if there is technically enough space.  Unless
> > perhaps it's some superfast swap that you have?
> 
> the swap partition is a standard qcow image stored on my SSD disk. So
> I guess the IO should be quite fast. This smells like a potential
> contributor because my reclaim seems to be much faster and that should
> lead to a more efficient reclaim (in the scanned/reclaimed sense).

Hmm... This looks like one of potential culprit. If page is in
writeback, it can't be migrated by compaction with MIGRATE_SYNC_LIGHT.
In this case, this page works as pinned page and prevent compaction.
It'd be better to check that changing 'migration_mode = MIGRATE_SYNC' at
'no_progress_loops > XXX' will help in this situation.

Thanks.