static_partitioner + global_control triggers an unbounded memory leak about onetbb

[lennoxho]

Here are my run logs
leak.txt

[pavelkumbrasev]

Hi @lennoxho, I was able to reproduce described behavior.
TL;DR
It seems that task_arena usage is a correct way to work-around this problem. Meanwhile, we will think what to do with the leak if task_arena is not used.

So basically it happens because with global_control you limit concurrency that all the internal arenas can share between each other. Therefore, each particular arena doesn't not know its actual concurrency limit but only one you explicitly set during construction or for default arena (one that will be used for simple parallel_for call for example) the concurrency will be a whole machine.
When you start parallel_for with static_partitioner it will create as many internal proxy tasks as normal tasks (proxy tasks are used to assign tasks to specific threads). Proxy tasks have a property they should be executed twice. When execute is called for the proxy task for the first time it will return actual task that it propagated. When execute is called for the second time proxy task can be deleted.
In your case each time you call parallel_for with static_partitioner it will create hardware_concurrency proxy tasks but because global_control is present the concurrency of the default arena will not be fully satisfied and some of the proxy tasks will be called only once so they never be destroyed.
Perhaps, the solution will be to check min(arena::concurrency, global_control::limitation) during execution of static_partitioner.