Re: [PATCH] fs, mm: account filp and names caches to kmemcg

[Michal Hocko]

On Mon 09-10-17 20:04:09, Michal Hocko wrote:
> [CC Johannes - the thread starts
> http://lkml.kernel.org/r/20171005222144.123797-1-shakeelb@xxxxxxxxxx]
> 
> On Mon 09-10-17 10:52:44, Greg Thelen wrote:
[...]
> > A few ideas on how to make it more flexible:
> > 
> > a) Go back to memcg oom killing within memcg charging.  This runs risk
> >    of oom killing while caller holds locks which oom victim selection or
> >    oom victim termination may need.  Google's been running this way for
> >    a while.

We can actually reopen this discussion now that the oom handling is
async due to the oom_reaper. At least for the v2 interface. I would have
to think about it much more but the primary concern for this patch was
whether we really need/want to charge short therm objects which do not
outlive a single syscall.
 
> > b) Have every syscall return do something similar to page fault handler:
> >    kmem allocations in oom memcg mark the current task as needing an oom
> >    check return NULL.  If marked oom, syscall exit would use
> >    mem_cgroup_oom_synchronize() before retrying the syscall.  Seems
> >    risky.  I doubt every syscall is compatible with such a restart.

yes, this is simply a no go

> > c) Overcharge kmem to oom memcg and queue an async memcg limit checker,
> >    which will oom kill if needed.

This is what we have max limit for.
-- 
Michal Hocko
SUSE Labs