Home » Mailing lists » Devel » Re: [ckrm-tech] [RFC] Resource Management - Infrastructure choices
| Re: [ckrm-tech] [RFC] Resource Management - Infrastructure choices [message #7980] |
Wed, 01 November 2006 21:18  |
Chris Friesen
Messages: 4
Registered: August 2006
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Junior Member |
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Srivatsa Vaddagiri wrote:
>>> - Support limit (soft and/or hard depending on the resource
>>> type) in controllers. Guarantee feature could be indirectly
>>> met thr limits.
I just thought I'd weigh in on this. As far as our usage pattern is
concerned, guarantees cannot be met via limits.
I want to give "x" cpu to container X, "y" cpu to container Y, and "z"
cpu to container Z.
If these are percentages, x+y+z must be less than 100.
However, if Y does not use its share of the cpu, I would like the
leftover cpu time to be made available to X and Z, in a ratio based on
their allocated weights.
With limits, I don't see how I can get the ability for containers to
make opportunistic use of cpu that becomes available.
I can see that with things like memory this could become tricky (How do
you free up memory that was allocated to X when Y decides that it really
wants it after all?) but for CPU I think it's a valid scenario.
Chris
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| Re: Re: [ckrm-tech] [RFC] Resource Management - Infrastructure choices [message #7981 is a reply to message #7980] |
Wed, 01 November 2006 23:01  |
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Chris Friesen wrote:
> Srivatsa Vaddagiri wrote:
>
>>>> - Support limit (soft and/or hard depending on the resource
>>>> type) in controllers. Guarantee feature could be indirectly
>>>> met thr limits.
>
> I just thought I'd weigh in on this. As far as our usage pattern is
> concerned, guarantees cannot be met via limits.
>
> I want to give "x" cpu to container X, "y" cpu to container Y, and "z"
> cpu to container Z.
>
> If these are percentages, x+y+z must be less than 100.
>
> However, if Y does not use its share of the cpu, I would like the
> leftover cpu time to be made available to X and Z, in a ratio based on
> their allocated weights.
>
> With limits, I don't see how I can get the ability for containers to
> make opportunistic use of cpu that becomes available.
This is basically how "cpuunits" in OpenVZ works. It is not limiting a
container in any way, just assigns some relative "units" to it, with sum
of all units across all containers equal to 100% CPU. Thus, if we have
cpuunits 10, 20, and 30 assigned to containers X, Y, and Z, and run some
CPU-intensive tasks in all the containers, X will be given
10/(10+20+30), or 20% of CPU time, Y -- 20/50, i.e. 40%, while Z gets
60%. Now, if Z is not using CPU, X will be given 33% and Y -- 66%. The
scheduler used is based on a per-VE runqueues, is quite fair, and works
fine and fair for, say, uneven case of 3 containers on a 4 CPU box.
OpenVZ also has a "cpulimit" resource, which is, naturally, a hard limit
of CPU usage for a VE. Still, given the fact that cpunits works just
fine, cpulimit is rarely needed -- makes sense only in special scenarios
where you want to see how app is run on a slow box, or in case of some
proprietary software licensed per CPU MHZ, or smth like that.
Looks like this is what you need, right?
> I can see that with things like memory this could become tricky (How
> do you free up memory that was allocated to X when Y decides that it
> really wants it after all?) but for CPU I think it's a valid scenario.
Yes, CPU controller is quite different of other resource controllers.
Kir.
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| Re: Re: [ckrm-tech] [RFC] Resource Management - Infrastructure choices [message #7983 is a reply to message #7981] |
Thu, 02 November 2006 00:31 |
Matt Helsley
Messages: 86
Registered: August 2006
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Member |
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On Thu, 2006-11-02 at 02:01 +0300, Kir Kolyshkin wrote:
> Chris Friesen wrote:
> > Srivatsa Vaddagiri wrote:
> >
> >>>> - Support limit (soft and/or hard depending on the resource
> >>>> type) in controllers. Guarantee feature could be indirectly
> >>>> met thr limits.
> >
> > I just thought I'd weigh in on this. As far as our usage pattern is
> > concerned, guarantees cannot be met via limits.
> >
> > I want to give "x" cpu to container X, "y" cpu to container Y, and "z"
> > cpu to container Z.
> >
> > If these are percentages, x+y+z must be less than 100.
> >
> > However, if Y does not use its share of the cpu, I would like the
> > leftover cpu time to be made available to X and Z, in a ratio based on
> > their allocated weights.
> >
> > With limits, I don't see how I can get the ability for containers to
> > make opportunistic use of cpu that becomes available.
> This is basically how "cpuunits" in OpenVZ works. It is not limiting a
> container in any way, just assigns some relative "units" to it, with sum
> of all units across all containers equal to 100% CPU. Thus, if we have
So the user doesn't really specify percentage but values that feed into
ratios used by the underlying controller? If so then it's not terribly
different from the "shares" of single level of Resource Groups.
Resource groups goes one step further and defines a denominator for
child groups to use. This allows the shares to be connected vertically
so that changes don't need to propagate beyond the parent and child
groups.
> cpuunits 10, 20, and 30 assigned to containers X, Y, and Z, and run some
> CPU-intensive tasks in all the containers, X will be given
> 10/(10+20+30), or 20% of CPU time, Y -- 20/50, i.e. 40%, while Z gets
nit: I don't think this math is correct.
Shouldn't they all have the same denominator (60), or am I
misunderstanding something?
If so then it should be:
X = 10/60 16.666...%
Y = 20/60 33.333...%
Z = 30/60 50.0%
Total: 100.0%
> 60%. Now, if Z is not using CPU, X will be given 33% and Y -- 66%. The
> scheduler used is based on a per-VE runqueues, is quite fair, and works
> fine and fair for, say, uneven case of 3 containers on a 4 CPU box.
<snip>
Cheers,
-Matt Helsley
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| Re: Re: [ckrm-tech] [RFC] Resource Management - Infrastructure choices [message #7988 is a reply to message #7983] |
Thu, 02 November 2006 08:34 |
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Matt Helsley wrote:
> On Thu, 2006-11-02 at 02:01 +0300, Kir Kolyshkin wrote:
>
>> cpuunits 10, 20, and 30 assigned to containers X, Y, and Z, and run some
>> CPU-intensive tasks in all the containers, X will be given
>> 10/(10+20+30), or 20% of CPU time, Y -- 20/50, i.e. 40%, while Z gets
>>
>
> nit: I don't think this math is correct.
>
> Shouldn't they all have the same denominator (60), or am I
> misunderstanding something?
>
> If so then it should be:
> X = 10/60 16.666...%
> Y = 20/60 33.333...%
> Z = 30/60 50.0%
> Total: 100.0%
>
Ughm. You are totally correct of course, I must've been very tired
yesterday night :-\
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