[slurm-users] Proposal for new TRES - "Processor Performance Units"....

Paul Edmon pedmon at cfa.harvard.edu
Thu Jun 20 15:28:26 UTC 2019

We don't do anything.  In our environment it is the user's 
responsibility to optimize their code appropriately.  Since we have a 
great variety of hardware any modules we build (we have several thousand 
of them) are all build generically.  If people want processor specific 
optimizations then they have to build their own stack.

-Paul Edmon-

On 6/20/19 11:07 AM, Fulcomer, Samuel wrote:
> ...ah, got it. I was confused by "PI/Lab nodes" in your partition list.
> Our QoS/account pair for each investigator condo is our approximate 
> equivalent of what you're doing with owned partitions.
> Since we have everything in one partition we segregate processor types 
> via topology.conf. We break up topology.conf further to keep MPI jobs 
> on the same switch.
> On another topic, how do you address code optimization for processor 
> type? We've been mostly linking with MKL and relying on its 
> muti-code-path.
> Regards,
> Sam
> On Thu, Jun 20, 2019 at 10:20 AM Paul Edmon <pedmon at cfa.harvard.edu 
> <mailto:pedmon at cfa.harvard.edu>> wrote:
>     People will specify which partition they need or if they want
>     multiple they use this:
>     #SBATCH -p general,shared,serial_requeue
>     As then the scheduler will just select which partition they will
>     run in first.  Naturally there is a risk that you will end up
>     running in a more expensive partition.
>     Our time limit is only applied to our public partitions, our owned
>     partitions (of which we have roughly 80) have no time limit.  So
>     if they run on their dedicated resources they have no penalty. 
>     We've been working on getting rid of owned partitions and moving
>     to a school/department based partition, where all the purchased
>     resources for different PI's go into the same bucket where they
>     compete against themselves and not the wider community.  We've
>     found that this ends up working pretty well as most PI's only used
>     their purchased resources sporadically.  Thus there are usually
>     idle cores lying around that we backfill with our serial queues. 
>     Since those are requeueable we can get immediate response to
>     access that idle space.  We are also toying with a high priority
>     partition that is open to people with high fairshare so that they
>     can get immediate response as those with high fairshare tend to be
>     bursty users.
>     Our current halflife is set to a month and we keep 6 months of
>     data in our database.  I'd actually like to get rid of the
>     halflife and just go to a 3 month moving window to allow people to
>     bank their fairshare, but we haven't done that yet as people have
>     been having a hard enough time understanding our current system. 
>     It's not due to its complexity but more that most people just flat
>     out aren't cognizant of their usage and think the resource is
>     functionally infinite.
>     -Paul Edmon-
>     On 6/19/19 5:16 PM, Fulcomer, Samuel wrote:
>>     Hi Paul,
>>     Thanks..Your setup is interesting. I see that you have your
>>     processor types segregated in their own partitions (with the
>>     exception of of the requeue partition), and that's how you get at
>>     the weighting mechanism. Do you have your users explicitly
>>     specify multiple partitions in the batch commands/scripts in
>>     order to take advantage of this, or do you use a plugin for it?
>>     It sounds like you don't impose any hard limit on simultaneous
>>     resource use, and allow everything to fairshare out with the help
>>     of the 7 day TimeLimit. We haven't been imposing any TimeLimit on
>>     our condo users, which would be an issue for us with your config.
>>     For our exploratory and priority users, we impose an effective
>>     time limit with GrpTRESRunMins=cpu (and gres/gpu= for the GPU
>>     usage). In addition, since we have so many priority users, we
>>     don't explicitly set a rawshare value for them (they all execute
>>     under the "default" account). We set rawshare for the condo
>>     accounts as cores-purchased/total-cores*1000.
>>     What's your fairshare decay setting (don't remember the proper
>>     name at the moment)?
>>     Regards,
>>     Sam
>>     On Wed, Jun 19, 2019 at 3:44 PM Paul Edmon
>>     <pedmon at cfa.harvard.edu <mailto:pedmon at cfa.harvard.edu>> wrote:
>>         We do a similar thing here at Harvard:
>>         https://www.rc.fas.harvard.edu/fairshare/
>>         We simply weight all the partitions based on their core type
>>         and then we allocate Shares for each account based on what
>>         they have purchased.  We don't use QoS at all, so we just
>>         rely purely on fairshare weighting for resource usage.  It
>>         has worked pretty well for our purposes.
>>         -Paul Edmon-
>>         On 6/19/19 3:30 PM, Fulcomer, Samuel wrote:
>>>         (...and yes, the name is inspired by a certain OEM's
>>>         software licensing schemes...)
>>>         At Brown we run a ~400 node cluster containing nodes of
>>>         multiple architectures (Sandy/Ivy, Haswell/Broadwell, and
>>>         Sky/Cascade) purchased in some cases by University funds and
>>>         in others by investigator funding (~50:50).  They all appear
>>>         in the default SLURM partition. We have 3 classes of SLURM
>>>         users:
>>>          1. Exploratory - no-charge access to up to 16 cores
>>>          2. Priority - $750/quarter for access to up to 192 cores
>>>             (and with a GrpTRESRunMins=cpu limit). Each user has
>>>             their own QoS
>>>          3. Condo - an investigator group who paid for nodes added
>>>             to the cluster. The group has its own QoS and SLURM
>>>             Account. The QoS allows use of the number of cores
>>>             purchased and has a much higher priority than the QoS'
>>>             of the "priority" users.
>>>         The first problem with this scheme is that condo users who
>>>         have purchased the older hardware now have access to the
>>>         newest without penalty. In addition, we're encountering
>>>         resistance to the idea of turning off their hardware and
>>>         terminating their condos (despite MOUs stating a 5yr life).
>>>         The pushback is the stated belief that the hardware should
>>>         run until it dies.
>>>         What I propose is a new TRES called a Processor Performance
>>>         Unit (PPU) that would be specified on the Node line in
>>>         slurm.conf, and used such that GrpTRES=ppu=N was calculated
>>>         as the number of allocated cores multiplied by their
>>>         associated PPU numbers.
>>>         We could then assign a base PPU to the oldest hardware, say,
>>>         "1" for Sandy/Ivy and increase for later architectures based
>>>         on performance improvement. We'd set the condo QoS to
>>>         GrpTRES=ppu=N*X+M*Y,..., where N is the number of cores of
>>>         the oldest architecture multiplied by the configured
>>>         PPU/core, X, and repeat for any newer nodes/cores the
>>>         investigator has purchased since.
>>>         The result is that the investigator group gets to run on an
>>>         approximation of the performance that they've purchased,
>>>         rather on the raw purchased core count.
>>>         Thoughts?
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