Re: [RFC] Low overhead patches for the memory resource controller

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

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-05-14 09:08:02]:

> On Wed, 13 May 2009 21:02:18 +0530
> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> 
> > Important: Not for inclusion, for discussion only
> > 
> > I've been experimenting with a version of the patches below. They add
> > a PCGF_ROOT flag for tracking pages belonging to the root cgroup and
> > disable LRU manipulation for them
> > 
> > Caveats:
> > 
> > 1. I've not checked accounting, accounting might be broken
> > 2. I've not made the root cgroup as non limitable, we need to disable
> > hard limits once we agree to go with this
> > 
> > 
> > Tests
> > 
> > Quick tests show an improvement with AIM9
> > 
> >                 mmotm+patch     mmtom-08-may-2009
> > AIM9            1338.57         1338.17
> > Dbase           18034.16        16021.58
> > New Dbase       18482.24        16518.54
> > Shared          9935.98         8882.11
> > Compute         16619.81        15226.13
> > 
> > Comments on the approach much appreciated
> > 
> > Feature: Remove the overhead associated with the root cgroup
> > 
> > From: Balbir Singh <balbir@linux.vnet.ibm.com>
> > 
> > This patch changes the memory cgroup and removes the overhead associated
> > with accounting all pages in the root cgroup. As a side-effect, we can
> > no longer set a memory hard limit in the root cgroup.
> > 
> > A new flag is used to track page_cgroup associated with the root cgroup
> > pages.
> 
> Hmm ? How about ignoring memcg completely when the thread belongs to ROOT
> cgroup rather than this halfway method ?
>

I wanted to keep root cgroup accounting, specially useful in the case
of hierarchical setup and even otherwise, we don't want those values
to disappear. May be in the longer run, we could decide to move
provided we get sufficient time to deprecate root cgroup stats.
 
-- 
	Balbir

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