Re: [patch 14/22] memcg: fix direct softlimit reclaim to be called in limit path

[Michal Hocko <mhocko@suse.cz>]

On Tue 28-06-11 17:06:49, KAMEZAWA Hiroyuki wrote:
> On Tue, 28 Jun 2011 10:08:47 +0200
> Michal Hocko <mhocko@suse.cz> wrote:
> 
> > I am sorry, that I am answering that late but I didn't get to this
> > sooner.
> > 
> > On Mon 27-06-11 16:18:12, Andrew Morton wrote:
> > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > > 
> > > commit d149e3b ("memcg: add the soft_limit reclaim in global direct
> > > reclaim") adds a softlimit hook to shrink_zones().  By this, soft limit is
> > > called as
> > > 
> > >    try_to_free_pages()
> > >        do_try_to_free_pages()
> > >            shrink_zones()
> > >                mem_cgroup_soft_limit_reclaim()
> > > 
> > > Then, direct reclaim is memcg softlimit hint aware, now.
> > > 
> > > But, the memory cgroup's "limit" path can call softlimit shrinker.
> > > 
> > >    try_to_free_mem_cgroup_pages()
> > >        do_try_to_free_pages()
> > >            shrink_zones()
> > >                mem_cgroup_soft_limit_reclaim()
> > > 
> > > This will cause a global reclaim when a memcg hits limit.
> > 
> > Sorry, I do not get it. How does it cause the global reclaim? Did you
> > mean soft reclaim?
> > 
> 
> yes. soft reclaim does global reclaim (in some means). 

But calling it global reclaim is rather confusing because in both paths
we have sc.mem_cgroup set to non-NULL which is evaluated as
!scanning_global_lru(sc). Anyway, this is not that important, I just
wanted to be sure what you meant by that comment.

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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