Re: [Condor-users] Confused about multiple slots, VM_MAX_NUMBER, and VM_MEMORY !?!

[Matthew Farrellee <matt@xxxxxxxxxx>]

Thanks for the good description and clarification. I did misspeak when I said you could give VM_MEMORY the amount of memory available on a slot.

Best,


matt


Jaeyoung Yoon wrote:
> Adding some comments to Matt's,
> 
> As matt said, VM_MAX_NUMBER and VM_MEMORY server as a second level of
> checks for VM jobs on the whole PC.
> 
> Originally VM_MAX_NUMBER was added to limit the number of VM jobs on
> the whole machine.  And VM_MEMORY was added to limit the amount of
> memory for VM jobs on the whole machine.
> 
> Let me give one example,
> 
> With your machine(2CPUS and 4GB RAM), by default Condor creates two
> slots (slot1 and slot2) where each slot has 2GB.
> 
> So you can run two Condor jobs(Vanilla, Standard, Java Universe etc.)
> concurrently. But when you set VM_MAX_NUMBER to 1, even if you have
> two slots, you can at most ONE VM job on the whole machine. That is,
> at most one slot can be assigned to VM job. Surely, it is possible
> that one slot for VM, the other slot for Vanilla.
> 
>  If you leave VM_MAX_NUMBER undefined or set to 0, the maximum number
> of running VM jobs is same to the number of Slots. In your case, the
> number is 2. But you can see "VM_MAX_NUMBER = 10000" in the machine's
> ClassAd. I know the number looks weird. But anyway "VM_MAX_NUMBER =
> 10000" in classAd means that the maximum number of running VM jobs on
> the machine is same to the number of slots.
> 
> VM_MEMORY is the total memory which can be assigned to VM jobs on the
> whole machine. It is not related to memory assigned to each slot. In
> submit file for VM jobs, you need to specify how much memory is
> necessary for the submitting VM job. The memory amount will be checked
> with "VM_MEMORY "in machine classAd.
> 
> Here is the example in your machine where slot1 and slot2 has each 1GB.
> Example 1)
> Supposed you set "VM_MAX_NUMBER = 1" and "VM_MEMORY = 1600", you can
> run at most one VM job which requires less and equal than 1600MB.
> Notice you can submit 1.6GB vm job even if each slot has 1GB.
> 
> Example 2)
> Supposed you set "VM_MAX_NUMBER = 0" and "VM_MEMORY = 1600", when you
> submit one VM job requiring 1.3GB memory, you can run the VM. But
> after the VM job is assigned to one slot, VM_MEMORY will be decreased
> to "300". So if you try to submit another VM job requiring 500MB
> memory, it will not be assigned to machine any more because VM_MEMORY
> is 300 at that time.
> 
> Best,
> -jaeyoung
> 
> On Tue, Aug 11, 2009 at 12:09 PM, Matthew Farrellee<matt@xxxxxxxxxx> wrote:
>> Rob wrote:
>>> Hello,
>>>
>>> I'd like to understand the concept of multi core PCs (which represent
>>> themselves as independent slots in the Condor pool), in relation to the
>>> VMware server for the VM Universe.
>>>
>>> For example, a dual core PC (2 CPUs) with 4 GB RAM appears as
>>> slot1 and slot2 in the condor_status list of the master and each slot
>>> gets 2 GB of the total physical RAM.
>>>
>>> What are the effects of VM_MAX_NUMBER and VM_MEMORY?
>>> Are the values defined with respect to the whole PC, or per slot?
>>>
>>> Should I allow two VMs or just one on a dual core PC?
>>> I suppose this choice then also effects how much RAM I can assign
>>> to a VM.....?!?
>>>
>>> Thanks!
>>> Rob.
>> The variables apply across the entire machine and really serve as a second level of checks that VM jobs must pass.
>>
>> You should be safe leaving VM_MAX_NUMBER undefined (or set to 0) and setting VM_MEMORY to however much memory is given to a slot.
>>
>> I'm actually consider removing these in favor of normal startd policy. For instance, if you have 4 cores and want to run only 2 VMs then you only advertise 2 slots. If you want no VMs to be over 1GB then you only advertise 1GB of memory on the slots. If you want a mix of VMs and jobs to run and want to constrain the VMs more then advertise 2 non-VM slots and 2 VM slots, where normal jobs can run on any of the 4.
>>
>> Have any thoughts on this?
>>
>> Best,
>>
>>
>> matt
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