AW: [GE users] resource allocation and race condition

Rod.Rebello at Microchip.com Rod.Rebello at Microchip.com
Fri Oct 15 22:43:55 BST 2004


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Although I can think of one situation where using a load sensor may be 
useful for flexlm license tracking , can you use a hard counter for the 
number of flexlm licenses?

For example, in our situation, we just set a global consumable counter to 
the number of flex licenses we have available and let SGE count up/down as 
resource requests are made.   Never had a race condition with this method. 
  Only drawback I see is that you now have to remember to update the 
counter resource whenever new licenses are added instead of automatically 
getting the info from flexlm.

The only problem we've had with this is when multiple grids all are 
accessing the same set of flexlm licenses.  This is where a load sensor 
may help to keep all the grids in sync.

Just curious, but is there any other reason why you need to use a load 
sensor for license tracking?

- Rod

----------------------------------------
Rod Rebello
Microchip Technology Inc.





Charu Chaubal <Charu.Chaubal at Sun.COM>
10/15/2004 08:21 AM
Please respond to users

 
        To:     users at gridengine.sunsource.net
        cc: 
        Subject:        Re: AW: [GE users] resource allocation and race condition



Hello,

Please see this HOWTO on tracking licenses with GE:
http://bioteam.net/dag/sge-flexlm-integration/

The HOWTO has all the details, but basically, you track a license with 
*both* a load sensor *and* a consumable resource simultaneously.  The 
GE master will then use whichever is the lower of the two values in 
order to avoid oversubscribing a license.  The HOWTO talks about how 
there's still the possibility of a race condition, and ways to deal 
with it.

Regards,
                 Charu

On Oct 15, 2004, at 8:19 AM, Olesen, Mark wrote:

>>> Assuming that I only have a single float license 'foo', I can
>>> 'qsub -l foo=1' a job.  After a while I submit two (2) new jobs with 
>>> the
>>> same resource requirement(s). Both these jobs wait politely in the
>> queue,
>>> since the resource 'foo' is unavailable.  After the first job 
>>> finishes,
>> and
>>> the load reports get correctly updated, *both* of the jobs in the 
>>> queue
>> try
>>> to grab the 'foo' resource (almost) simultaneously.
>>> How can I circumvent such a race condition?
>>
>> Could you use a SGE consumable in addition to your load sensor? - 
>> Reuti
>
>
> Based on what I can read from host_conf(5) about 'complex_values', I'd 
> have
> to alter the load sensor so that it only tracks non-SGE license use 
> rather
> than reporting the number of licenses currently available for use.
>
> This means that the load sensor needs to distinguish between 
> applications
> that were started with/without SGE. If accomplished, this would make 
> the
> load sensor anything other than lightweight.
>
> Is there a direct way, or a backdoor, to determine how many resources 
> SGE
> believes are still free and/or have been allocated?  Perhaps this 
> could be a
> means of adjusting the load sensor values.
>
> /mark
>
> Dr. Mark Olesen
> Thermofluid Dynamics Analyst
> ArvinMeritor Light Vehicle Systems
> ArvinMeritor Emissions Technologies GmbH
> Biberbachstr. 9
> D-86154 Augsburg, GERMANY
> tel: +49 (821) 4103 - 862
> fax: +49 (821) 4103 - 7862
> Mark.Olesen at ArvinMeritor.com
>
>> -----Ursprüngliche Nachricht-----
>> Von: Reuti [mailto:reuti at staff.uni-marburg.de]
>> Gesendet: Freitag, 15. Oktober 2004 11:00
>> An: users at gridengine.sunsource.net
>> Betreff: Re: [GE users] resource allocation and race condition
>>
>>
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###############################################################
# Charu V. Chaubal  # Phone: (650) 786-7672 (x87672)
# Grid Computing Technologist            # Fax:   (650) 786-4591
# Sun Microsystems, Inc.                                                 # 
Email: charu.chaubal at sun.com
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