"with-items" tasks work several times slower if the property "concurrency" is set

[Renat Akhmerov]

Consider the following workflow:

with_items_2000:
  tasks:
    task1:
      with-items: i in <% range(0, 2000) %>
      action: std.echo output=<% $.i %>
      concurrency: 100

The execution time of this workflow on MacBook Pro on one Mistral engine is about 9 min 52 sec. However, if we remove "concurrency: 100" the execution time is about 2 min 16 sec, so it's about 5 times faster.

Theoretically, if we don't use multiple engines that compete on DB objects the execution time in both cases should be similar.