Re: memcg reclaim demotion wrt. isolation

[Michal Hocko]

On Wed 14-12-22 10:57:52, Huang, Ying wrote:
> Michal Hocko <mhocko@xxxxxxxx> writes:
[...]
> > This makes sense but I suspect that this wasn't intended also for
> > memcg triggered reclaim. This would mean that a memory pressure in one
> > hierarchy could trigger paging out pages of a different hierarchy if the
> > demotion target is close to full.
> 
> It seems that it's unnecessary to wake up kswapd of demotion target node
> in most cases.  Because we will try to reclaim on the demotion target
> nodes in the loop of do_try_to_free_pages().  It may be better to loop
> the zonelist in the reverse order.  Because the demotion targets are
> usually located at the latter of the zonelist.

Reclaiming from demotion targets first would deal with that as well.
Thanks! Let's establish whether this is something we really need/want
fix first.
-- 
Michal Hocko
SUSE Labs