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Subject: Re: [OMPI users] Xgrid and choosing agents...
From: Klymak Jody (jklymak_at_[hidden])
Date: 2009-07-11 18:11:32


If anyone else is using xgrid, there is a mechanism to limit the
processes per machine:

sudo defaults write /Library/Preferences/com.apple.xgrid.agent
MaximumTaskCount 8

on each of the nodes and then restarting xgrid tells the controller to
only send 8 processes to that node. For now that is fine solution for
my need. I'll try and figure out how to specify hosts via xgrid and
get back to the list...

Thanks for everyone's help,

Cheers, Jody

On 11-Jul-09, at 12:42 PM, Ralph Castain wrote:

> Looking at the code, you are correct in that the Xgrid launcher is
> ignoring hostfiles. I'll have to look at it to determine how to
> correct that situation - I didn't write that code, nor do I have a
> way to test any changes I might make to it.
>
> For now, though, if you add --bynode to your command line, you
> should get the layout you want. I'm not sure you'll get the rank
> layout you'll want, though...or if that is important to what you are
> doing.
>
> Ralph
>
> On Jul 11, 2009, at 1:18 PM, Klymak Jody wrote:
>
>> Hi Vitorio,
>>
>> Thanks for getting back to me! My hostfile is
>>
>> xserve01.local max-slots=8
>> xserve02.local max-slots=8
>> xserve03.local max-slots=8
>> xserve04.local max-slots=8
>>
>> I've now checked, and this seems to work fine just using ssh. i.e.
>> if I turn off the Xgrid queue manager I can submit jobs manually to
>> the appropriate nodes using --hosts.
>>
>> However, I'd really like to use Xgrid as my queue manager as it is
>> already set up (though I'll happily take hints on how to set up
>> other queue managers on an OS X cluster).
>>
>>> So you have 4 nodes each one with 2 processors, each processor 4-
>>> core - quad-core.
>>> So you have capacity for 32 process in parallel.
>>
>> The new Xeon chips designate 2-processes per core, though at a
>> reduced clock rate. This means that Xgrid believes I have 16
>> processors/node. For large jobs I expect that to be useful, but
>> for my more modest jobs I really only want 8 processes/node.
>>
>> It appears that the default way xgrid assigns the jobs is to fill
>> all 16 slots on one node before moving to the next. OpenMPI
>> doesn't appear to look at the hostfile configuration when using
>> Xgrid, so it makes it hard for me to deprecate this behaviour.
>>
>> Thanks, Jody
>>
>>
>>
>>> I think that only using the hostfile is enough is how I use. If
>>> you to specify a specific host or a different sequence, the mpirun
>>> will obey the host sequence in your hostfile to start the process,
>>> also can you put how you configured your host files ? I'm asking
>>> this because you should have something like:
>>> # This is an example hostfile. Comments begin with
>>> # #
>>> # The following node is a single processor machine:
>>> foo.example.com
>>> # The following node is a dual-processor machine:
>>> bar.example.com slots=2
>>> # The following node is a quad-processor machine, and we absolutely
>>> # want to disallow over-subscribing it:
>>> yow.example.com slots=4 max-slots=4
>>> so in your case like mine you should have something like:
>>> your.hostname.domain slots=8 max-slots=8 # for each node
>>>
>>> I hope this will help you.
>>> Regards.
>>> Vitorio.
>>>
>>>
>>> Le 09-07-11 à 10:56, Klymak Jody a écrit :
>>>
>>>> Hi all,
>>>>
>>>> Sorry in advance if these are naive questions - I'm not
>>>> experienced in running a grid...
>>>>
>>>> I'm using openMPI on 4 duo Quad-core Xeon xserves. The 8 cores
>>>> mimic 16 cores and show up in xgrid as each agent having 16
>>>> processors. However, the processing speed goes down as the used
>>>> processors exceeds 8, so if possible I'd prefer to not have more
>>>> than 8 processors working on each machine at a time.
>>>>
>>>> Unfortunately, if I submit a 16-processor job to xgrid it all
>>>> goes to "xserve03". Or even worse, it does so if I submit two
>>>> separate 8-processor jobs. Is there anyway to steer jobs to less-
>>>> busy agents?
>>>>
>>>> I tried making a hostfile and then specifying the host, but I get:
>>>>
>>>> /usr/local/openmpi/bin/mpirun -n 8 --hostfile hostfile --host
>>>> xserve01.local ../build/mitgcmuv
>>>>
>>>> Some of the requested hosts are not included in the current
>>>> allocation for the
>>>> application:
>>>> ../build/mitgcmuv
>>>> The requested hosts were:
>>>> xserve01.local
>>>>
>>>> so I assume --host doesn't work with xgrid?
>>>>
>>>> Is a reasonable alternative to simply not use xgrid and rely on
>>>> ssh?
>>>>
>>>> Thanks, Jody
>>>>
>>>> --
>>>> Jody Klymak
>>>> http://web.uvic.ca/~jklymak
>>>>
>>>> _______________________________________________
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>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
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