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 09:24:05]:

> On Thu, 14 May 2009 09:08:02 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> 
> > 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 ? 
> > 
> BTW, this will make softlimit much harder. Do you have any idea on softlimit after
> this patch ?
>

Why would this make soft limit much harder? Since we charge up
hierarchially even now we ignore a cgroup if its soft limit is not
set. I am not sure I understand why. 

-- 
	Balbir

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