Running Parallel Tasks in Batch

0
votes

I have few questions about running tasks in parallel in Azure Batch. Per the official documentation, "Azure Batch allows you to set maximum tasks per node up to four times (4x) the number of node cores."

  1. Is there a setup other than specifying the max tasks per node when creating a pool, that needs to be done (to the code) to be able to run parallel tasks with batch?

  2. So if I am understanding this correctly, if I have a Standard_D1_v2 machine with 1 core, I can run up to 4 concurrent tasks running in parallel in it. Is that right? If yes, I ran some tests and I am quite not sure about the behavior that I got. In a pool of D1_v2 machines set up to run 1 task per node, I get about 16 min for my job execution time. Then, using the same applications and same parameters with the only change being a new pool with same setup, also D1_v2, except running 4 tasks per node, I still get a job execution time of about 15 min. There wasn't any improvement in the job execution time for running tasks in parallel. What could be happening? What am I missing here?

  3. I ran a test with a pool of D3_v2 machines with 4 cores, set up to run 2 tasks per core for a total of 8 tasks per node, and another test with a pool (same number of machines as previous one) of D2_v2 machines with 2 cores, set up to run 2 tasks per core for a total of 4 parallel tasks per node. The run time/ job execution time for both these tests were the same. Isn't there supposed to be an improvement considering that 8 tasks are running per node in the first test versus 4 tasks per node in the second test? If yes, what could be a reason why I'm not getting this improvement?

1
azure-batch

1 Answers

1
votes
  1. No. Although you may want to look into the task scheduling policy, compute node fill type to control how your tasks are distributed amongst nodes in your pool.
  2. How many tasks are in your job? Are your tasks compute-bound? If so, you won't see any improvement (perhaps even end-to-end performance degradation).
  3. Batch merely schedules the tasks concurrently on the node. If the command/process that you're running utilizes all of the cores on the machine and is compute-bound, you won't see an improvement. You should double check your tasks start and end times within the job and the node execution info to see if they are actually being scheduled concurrently on the same node.