Massively parallel on single core? Post: 302395115

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Special Forums UNIX and Linux Applications High Performance Computing Massively parallel on single core? Post 302395115 by Andre_Merzky on Monday 15th of February 2010 04:23:34 AM

02-15-2010

Registered User

Hi Neo,

thanks for your reply!

I agree abut your remark as distributed architectures. This is my day-job, and I like it a lot :-)

I did not make the problem clear enough I think: the workload I am talking about are mostly idle jobs, so the CPU and memory load for each job is *very* low. Yes, I can beat the problem with more cores or nodes, but that seems very much like a waste, as those would be all idling most of the time.

Assume you plan for 1000 threads per core, and use quad code nodes - that would require 25 nodes which all idle all day long :-(

Some more detail, if that helps: the idle processes/threads are basically watchers, which represent a CPU/Memory heavy remote job they spawned, and whose state they are watching. Only when that state changes they become active, and kick of data movements or spawn new jobs.

We can't control the design of the remote job startup API very well (third party, synchronous API only), thus our technical options for obtaining state information about those jobs are limited, and boil down to

Code:

void * run_job (void * data)
{
   // this call runs a remote job, and blocks for hours
   remote_api_call (data);
   store_output_data (data);
}

#define NJOBS 100000

int main ()
{
  pthread_t threads[NJOBS]
  for ( int i = 0; i < NJOBS; i++ )
  {
     pthread_create (threads[i],  run_job, ...)
  }

  for ( int i = 0; i < NJOBS; i++ )
  {
     pthread_join (threads[i]);
  }
}

So, I can throw 25 nodes on that large for loop, and that is what we do basically - but what a waste...

The *real* workload are 100.000 CPU/Memory heavy remote jobs, which have sufficient resources to run concurrently. I am talking about the management side (our workflow engine).

Thanks, Andre.

Andre_Merzky

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ns_job

ns_job(3aolserver)					    AOLserver Built-In Commands 					ns_job(3aolserver)

__________________________________________________________________________________________________________________________________________________

NAME

       ns_job - commands

SYNOPSIS

       ns_job option ?arg arg ...?

       ns_job create ?-desc description? queueId ?maxthreads?

       ns_job queue ?-detached? queueId  script

       ns_job wait ?-timeout seconds:microseconds? queueId  jobId

       ns_job waitany ?-timeout seconds:microseconds? queueId

       ns_job cancel queueId jobId

       ns_job delete queueId

       ns_job jobs queueId

       ns_job queues

       ns_job threadlist

       ns_job queuelist

       ns_job joblist

       ns_job genid

_________________________________________________________________

DESCRIPTION

       ns_job manages a thread pool and a set of named "queues". Queues have a max number of threads and when the current number of running thread
       reaches "max" then jobs are queued.

       New threads are created when there are less than  maxthread  number of idle threads.

OPTIONS

       create

	      create ?-desc description? queueId ?maxthreads?

	      Create a new job queue called queueId. If maxthreads is not specified, then the default of 4 is used.

       queue

	      queue ?-detached? queueId script

	      Add a new job to the queue. If there are less than maxthreads current running then the job will be started. If there are	maxthreads
	      currently running then this new job will be queued.

	      If detached is true, then the job will be cleaned up when it completes; no wait will be necessary.

	      The new job's ID is returned.

       wait

	      wait ?-timeout seconds:microseconds? queueId jobId

	      Wait for the specified queued or running job to finish. wait returns the results of the script.

	      An error is thrown if the specified timeout period is reached.

       waitany

	      waitany ?-timeout seconds:microseconds? queueId

	      Wait for any job on the queue complete.

	      An error is thrown if the specified timeout period is reached.

       cancel

	      cancel queueId jobId

	      Remove  the  specified job from the queue. If the job is currently running, then the job will be removed from the queue when it com-
	      pletes.

	      1 (true)	is returned if the job is currently running and can not be cancelled.

       delete

	      delete queueId

	      Request that the specified queue be deleted. The queue will only be deleted when all jobs are removed.

       jobs

	      jobs queueId

	      Return a list of the job IDs.

       queues

	      Returns a list of the queues IDs.

       threadlist

	      Returns a list of the thread pool's fields.

	      maxthreads
		     Max number of threads for all the queues in the thread pool.

	      numthreads
		     Number of allocated threads.

	      numidle
		     Number of currently idle threads.

	      req
		     stop
			    The thread pools is being stopped. This probably means that the server is shutting down.

       queuelist

	      Returns a list of the queues. A queue has the following fields:

	      name
		     Name of the queue.

	      desc
		     Description of the queue.

	      maxthreads
		     Max number of threads to run for this queue.

	      numrunning
		     Number of currently running jobs in this queue.

	      REQ
		     delete
			    Someone requested this queue be deleted. Queue will not be deleted until all the jobs on the queue are removed.

       joblist

	      Returns a list the jobs in the specified queue. A job has the following fields:

	      id
		     Job's ID

	      state
		     scheduled
			    The job is schedule to run.
		     running
			    The job is currently running.
		     done
			    The job is has completed.

	      results
		     If the job has completed, then this field will contain the results. If the job is running or scheduled to run, then this will
		     contain the script.

	      code
		     When the job is done, this will contain the return code.
			    Codes
				    TCL_OK
				    TCL_ERROR
				    TCL_RETURN
				    TCL_BREAK
				    TCL_CONTINUE

	      TYPE
		      nondetached
		      detached

	      REQ
		      none
		      wait
		      cancel

       genid

	      Generate a new unique ID. This new ID can be used as the queue ID without conflicting with any other queue ID.

BUGS

SEE ALSO

       nsd(1), info(n)

KEYWORDS

       ns_job

AOLserver								4.0							ns_job(3aolserver)