Re: [PATCH v2] mm: memcg: update memcg OOM messages on cgroup2

[Tejun Heo <tj@kernel.org>]

On Tue, Aug 07, 2018 at 09:13:32AM +0200, Michal Hocko wrote:
> > * It's the same information as memory.stat but would be in a different
> >   format and will likely be a bit of an eyeful.
> >
> > * It can easily become a really long line.  Each kernel log can be ~1k
> >   in length and there can be other limits in the log pipeline
> >   (e.g. netcons).
> 
> Are we getting close to those limits?

Yeah, I think the stats we have can already go close to or over 500
bytes easily, which is already pushing the netcons udp packet size
limit.

> > * The information is already multi-line and cgroup oom kills don't
> >   take down the system, so there's no need to worry about scroll back
> >   that much.  Also, not printing recursive info means the output is
> >   well-bound.
> 
> Well, on the other hand you can have a lot of memcgs under OOM and then
> swamp the log a lot.

idk, the info dump is already multi-line.  If we have a lot of memcgs
under OOM, we're already kinda messed up (e.g. we can't tell which
line is for which oom).  This adds to that to a certain extent but not
by much.  In practice, this doesn't seem to be a signficant problem.

Thanks.

-- 
tejun