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Subject: Re: [ckrm-tech] [PATCH] BC: resource
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From: Chandra Seetharaman <sekharan@us.ibm.com>
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On Tue, 2006-09-12 at 17:39 -0700, Rohit Seth wrote:
<snip>
> > yes, it would be there, but is not heavy, IMO.
> 
> I think anything greater than 1% could be a concern for people who are
> not very interested in containers but would be forced to live with them.

If they are not interested in resource management and/or containers, i
do not think they need to pay.
> 
> > > 
> > > > > 
> > > > > And anything running outside a container should be limited by default
> > > > > Linux settings.
> > > > 
> > > > note that the resource available to the default RG will be (total system
> > > > resource - allocated to RGs).
> > > 
> > > I think it will be preferable to not change the existing behavior for
> > > applications that are running outside any container (in your case
> > > default resource group).
> > 
> > hmm, when you provide QoS for a set of apps, you will affect (the
> > resource availability of) other apps. I don't see any way around it. Any
> > ideas ?
> 
> When I say, existing behavior, I mean not getting impacted by some
> artificial limits that are imposed by container subsystem.  IOW, if a

That is what I understood and replied above.
> sysadmin is okay to have certain apps running outside of container then
> he is basically forgoing any QoS for any container on that system.

Not at all. If the container they are interested in is guaranteed, I do
not see how apps running outside a container would affect them.

<snip>
> > > > Not really. 
> > > >  - Each RG will have a guarantee and limit of each resource. 
> > > >  - default RG will have (system resource - sum of guarantees)
> > > >  - Every RG will be guaranteed some amount of resource to provide QoS
> > > >  - Every RG will be limited at "limit" to prevent DoS attacks.
> > > >  - Whoever doesn't care either of those set them to don't care values.
> > > > 
> > > 
> > > For the cases that put this don't care, do you depend on existing
> > > reclaim algorithm (for memory) in kernel?
> > 
> > Yes.
> 
> So one container with these don't care condition(s) can turn the whole
> guarantee thing bad.  Because existing kernel reclaimer does not know
> about memory commitments to other containers.  Right?

No, the reclaimer would free up pages associated with the don't care RGs
( as the user don't care about the resource made available to them).

<snip>
> > > If the limits are set appropriately so that containers total memory
> > > consumption does not exceed the system memory then there shouldn't be
> > > any QoS issue (to whatever extent it is applicable for specific
> > > scenario).
> > 
> > Then you will not be work-conserving (IOW over-committing), which is one
> > of the main advantage of this type of feature.
> > 
> 
> If for the systems where QoS is important, not over-committing will be
> fine (at least to start with).

The problem is that you can't do it with just limit.

-- 

----------------------------------------------------------------------
    Chandra Seetharaman               | Be careful what you choose....
              - sekharan@us.ibm.com   |      .......you may get it.
----------------------------------------------------------------------


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