[GE users] h_vmem? virtual_free? mem_free?

Reuti reuti at staff.uni-marburg.de
Thu Apr 14 10:10:26 BST 2005


it depends what you want to achieve with a memory request. So I can tell 
you, what we are doing:

- make the complex virtual_free consumable, requestable, default 300M for us

- give each host an amount a little bit less than the physical installed 
memory, e.g. 900M for a 1GB node.

So, the users can request their assumed amount of memory they need, 
without being killed if they need a little bit more. We prefer this 
setup, as you have to give to some applications the amount of memory for 
the user data - but the program in total will need a little bit more. I 
found it a cumbersome solution to state in the inputfile 400MB and to 
submit with a request limit of 450M. They should request the same amount.

As long as the users are fair, they will only use some swap space really 
rarely with this setup. And if the submit the job with a virtual_free=0 
to get a node (although there is no memory left), they will hurt each 
other by swapping and learn not to do it.

Cheers - Reuti

Sebastian Stark wrote:
> Hi,
> Thank you for answering.
> On Wednesday 13 April 2005 17:44, Andreas Haas wrote:
>>Hi Sebastian,
>>I recommend use of h_vmem as per host consumable. Reason is
>>in contrast to mem_free the h_vmem is a regular resource limit
>>that is enforced on a per job basis!
> Sorry, I do not understand what that means. I do not want to limit the maximum 
> amount of memory a job may use, I just want to make sure it does not run on a 
> machine where another job is already running that has requested a lot of 
> memory (but is not yet using it).
>>As capacity for h_vmem you can use mem_total or virtual_total
>>depending on your needs. Though there is no means to automatically
>>use mem_total/virtual_total memory value as per host h_vmem
>>capacity, but you can use scripting interface to configure this.
> Do you mean (assuming my hosts have 8GB of real mem each) I should do:
>   qconf -mattr exechost complex_values mem_total=7.7G [listofnodes]
> ? What would be the difference if I'd use virtual_total instead?
> Sebastian

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