[Devel] Re: [ckrm-tech] [PATCH] BC: resource beancounters (v4) (added user memory)

[Chandra Seetharaman]

On Wed, 2006-09-13 at 12:06 +0400, Pavel Emelianov wrote:
> Chandra Seetharaman wrote:
> > On Tue, 2006-09-12 at 14:48 +0400, Pavel Emelianov wrote:
> > <snip>
> >   
> >>> I do not think it is that simple since
> >>>  - there is typically more than one class I want to set guarantee to
> >>>  - I will not able to use both limit and guarantee
> >>>  - Implementation will not be work-conserving.
> >>>
> >>> Also, How would you configure the following in your model ?
> >>>
> >>> 5 classes: Class A(10, 40), Class B(20, 100), Class C (30, 100), Class D
> >>> (5, 100), Class E(15, 50); (class_name(guarantee, limit))
> >>>   
> >>>       
> >> What's the total memory amount on the node? Without it it's hard to make
> >> any
> >> guarantee.
> >>     
> >
> > I wrote the example treating them as %, so 100 would be the total amount
> > of memory.
> >   
> OK. Then limiting must be done this way (unreclaimable limit/total limit)
> A (15/40)
> B (25/100)
> C (35/100)
> D (10/100)
> E (20/50)
> In this case each group will receive it's guarantee for sure.
> 
> E.g. even if A, B, E and D will eat all it's unreclaimable memory then
> we'll have
> 100 - 15 - 25 - 20 - 10 = 30% of memory left (maybe after reclaiming) which
> is perfectly enough for C's guarantee.

How did you arrive at the +5 number ?

What if I have 40 containers each with 2% guarantee ? what do we do
then ? and many other different combinations (what I gave was not the
_only_ scenario).

> >   
> >>> "Limit only" approach works for DoS prevention. But for providing QoS
> >>> you would need guarantee.
> >>>   
> >>>       
> >> You may not provide guarantee on physycal resource for a particular group
> >> without limiting its usage by other groups. That's my major idea.
> >>     
> >
> > I agree with that, but the other way around (i.e provide guarantee for
> > everyone by imposing limits on everyone) is what I am saying is not
> > possible.
> Then how do you make sure that memory WILL be available when the group needs
> it without limiting the others in a proper way?

You could limit others only if you _know_ somebody is not getting what
they are supposed to get (based on guarantee).

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