Re: [PATCH 4/4] Memory controller soft limit reclaim on contention (v6)

[Balbir Singh <balbir@linux.vnet.ibm.com>]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-03-17 15:00:58]:

> On Tue, 17 Mar 2009 11:25:06 +0530
> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> 
> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-03-17 14:17:14]:
> > > > That is not true..we don't track them to default cgroup unless
> > > > memory.use_hiearchy is enabled in the root cgroup. 
> > > What I want to say is "the task which is not attached to user's cgroup is
> > > also under defaut cgroup, so we don't need additional hook"
> > > Not talking about hierarchy.
> > >
> > 
> > Since all the user pages are tracked in one or the other cgroup, the
> > total accounting is equal to total_lru_pages across all zones/nodes.
> > Your suggestion boils down to if total_lru_pages reaches a threshold,
> > do soft limit reclaim, instead of doing reclaim when there is
> > contention.. right?
> >  
> Yes.
>

May I suggest that we first do the reclaim on contention and then
later on enhance it to add sysctl vm.soft_limit_ratio. I am not
proposing the soft limit patches for 2.6.30, but I would like to get
them in -mm for wider testing. If in that process the sysctl seems
more useful and applicable, we can consider adding it. Adding it right
now makes the reclaim logic more complex, having to check if we hit
the vm ratio quite often. Do you agree?
 
> 
> > > It's not necessary. for example, reading vmstat doesn't need global lock.
> > >
> > 
> > It uses atomic values for accounting. 
> > 
> Ah, my point is that "when it comes to usage of global LRU,
> accounting pages is already done somewhere. we can reuse it."
> Not means "add some new counter"
>

OK. 

-- 
	Balbir

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