linux-kernel - Re: [patch00/05]: Containers(V2)- Introduction

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Date:	Wed, 20 Sep 2006 11:07:58 -0700
From:	Rohit Seth <rohitseth@...gle.com>
To:	Christoph Lameter <clameter@....com>
Cc:	CKRM-Tech <ckrm-tech@...ts.sourceforge.net>, devel@...nvz.org,
	pj@....com, npiggin@...e.de,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch00/05]: Containers(V2)- Introduction

On Wed, 2006-09-20 at 10:38 -0700, Christoph Lameter wrote:
> On Wed, 20 Sep 2006, Rohit Seth wrote:
> 
> > cpusets provides cpu and memory NODES binding to tasks.  And I think it
> > works great for NUMA machines where you have different nodes with its
> > own set of CPUs and memory.  The number of those nodes on a commodity HW
> > is still 1.  And they can have 8-16 CPUs and in access of 100G of
> > memory.  You may start using fake nodes (untested territory) to
> 
> See linux-mm. We just went through a series of tests and functionality 
> wise it worked just fine.
> 

I thought the fake NUMA support still does not work on x86_64 baseline
kernel.  Though Paul and Andrew have patches to make it work.

> > translate a single node machine into N different nodes.  But am not sure
> > if this number of nodes can change dynamically on the running machine or
> > a reboot is required to change the number of nodes.
> 
> This is commonly discussed under the subject of memory hotplug.
> 

So now we depend on getting memory hot-plug to work for faking up these
nodes ...for the memory that is already present in the system. It just
does not sound logical.

> > Though when you want to have in access of 100 containers then the cpuset
> > function starts popping up on the oprofile chart very aggressively.  And
> > this is the cost that shouldn't have to be paid (particularly) for a
> > single node machine.
> 
> Yes this is a new way of using cpusets but it works and we could fix the 
> scalability issues rather than adding new subsystems.
> 

I think when you have 100's of zones then cost of allocating a page will
include checking cpuset validation and different zone list traversals
and checks...unless there is major surgery.

> > And what happens when you want to have cpuset with memory that needs to
> > be even further fine grained than each node.
> 
> New node?
> 

Am not clear how is this possible.  Could you or Paul please explain.

> > Containers also provide a mechanism to move files to containers. Any
> > further references to this file come from the same container rather than
> > the container which is bringing in a new page.
> 
> Hmmmm... Thats is interesting.
> 
> > In future there will be more handlers like CPU and disk that can be
> > easily embeded into this container infrastructure.
> 
> I think we should have one container mechanism instead of multiple. Maybe 
> merge the two? The cpuset functionality is well established and working 
> right.
> 

I agree that we will need one container subsystem in the long run.
Something that can easily adapt to different configurations.

-rohit

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