Re: [LSF/MM TOPIC] dying memory cgroups and slab reclaim issues

[Roman Gushchin <guro@fb.com>]

On Thu, Feb 21, 2019 at 02:46:17PM -0800, Roman Gushchin wrote:
> On Wed, Feb 20, 2019 at 06:27:07PM +1100, Dave Chinner wrote:
> > On Wed, Feb 20, 2019 at 04:50:31PM +1100, Dave Chinner wrote:
> > > I'm just going to fix the original regression in the shrinker
> > > algorithm by restoring the gradual accumulation behaviour, and this
> > > whole series of problems can be put to bed.
> > 
> > Something like this lightly smoke tested patch below. It may be
> > slightly more agressive than the original code for really small
> > freeable values (i.e. < 100) but otherwise should be roughly
> > equivalent to historic accumulation behaviour.
> > 
> > Cheers,
> > 
> > Dave.
> > -- 
> > Dave Chinner
> > david@fromorbit.com
> > 
> > mm: fix shrinker scan accumulation regression
> > 
> > From: Dave Chinner <dchinner@redhat.com>
> 
> JFYI: I'm testing this patch in our environment for fixing
> the memcg memory leak.
> 
> It will take a couple of days to get reliable results.
> 

So unfortunately the proposed patch is not solving the dying memcg reclaim
issue. I've tested it as is, with s/ilog2()/fls(), suggested by Johannes,
and also with more a aggressive zero-seek slabs reclaim (always scanning
at least SHRINK_BATCH for zero-seeks shrinkers). In all cases the number
of outstanding memory cgroups grew almost linearly with time and didn't show
any signs of plateauing.

Thanks!