On Thu, 19 Dec 2013 15:41:34 +0100 Michal Hocko [off-list ref] wrote:

On Wed 18-12-13 22:09:12, David Rientjes wrote:

quoted

On Wed, 18 Dec 2013, Michal Hocko wrote:

quoted

quoted

For memory isolation, we'd only want to bypass memcg charges when 
absolutely necessary and it seems like TIF_MEMDIE is the only case where 
that's required.  We don't give processes with pending SIGKILLs or those 
in the exit() path access to memory reserves in the page allocator without 
first determining that reclaim can't make any progress for the same reason 
and then we only do so by setting TIF_MEMDIE when calling the oom killer.  

While I do understand arguments about isolation I would also like to be
practical here. How many charges are we talking about? Dozen pages? Much
more?

The PF_EXITING bypass is indeed much less concerning than the 
fatal_signal_pending() bypass.

I just spent a happy half hour reliving this thread and ended up
deciding I agreed with everyone!  I appears that many more emails are
needed so I think I'll drop
http://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-avoid-oom-notification-when-current-needs-access-to-memory-reserves.patch
for now.

The claim that
mm-memcg-avoid-oom-notification-when-current-needs-access-to-memory-reserves.patch
will impact existing userspace seems a bit dubious to me.

OK, so can we at least agree on the patch posted here:
https://lkml.org/lkml/2013/12/12/129. This is a real bug and definitely
worth fixing.

Yes, can we please get Eric's bug fixed?  I don't believe that Eric has
tested either https://lkml.org/lkml/2013/12/12/129 or
http://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-avoid-oom-notification-when-current-needs-access-to-memory-reserves.patch.
Is he the only person who can reproduce this?