Hi all, I was rummaging around in the code looking for ideas just now and figured I might save myself some time by asking on the list to see if anyone else has encountered this. A quick review of the use case: we are using large stack sizes (2 MiB right now, though we could probably go lower but it will still be much larger than the ABT default). We also create, execute, and complete a large number of detached ULTs. Only a very few are intentionally long lived. Our current strategy is that a central producer (who drives network progress) creates ULTs that may be placed on other pools/ESs depending on configuration. I had *thought* that the ULT stacks were not allocated until the ULT was selected for execution by a scheduler, but I see now that's not the case. The stack is allocated up front at ABT_thread_create() time. I'm kicking myself for not understanding that sooner. It didn't matter so much when we used to use small stack sizes. At any rate, at this point this strategy has a few implications. If the ES schedulers don't retire old ULTs fast enough (even if they are very "close" to completion) then we can balloon memory consumption even if it doesn't look like our actual concurrency is all that high, simply because we are greedily taking more memory for stacks without regard to ULT completion. Secondly, the one producer is always paying the allocation cost, and the memory is always local to that one core. What would be ideal for me would be if ABT_thread_create() would defer stack allocation somehow. Ideally not consuming so much memory for a thread until a) it can really be executed and b) the scheduler thinks it is a good idea to do so. Even better if the the allocation were in the context of the ES that popped the thread, rather than the ES that spawned the thread. Is this possible? It would be neat if this could be done internal to Argobots somehow for generality for my use case, but walking through the code I have the sinking feeling that we need to do this above Argobots (explicitly queueing up work and letting the "worker" execution streams create their own ULTs to perform that work a needed, rather than letting the ULT pools within Argobots serve double duty as our work queue). I'm comfortable with custom pools and schedulers, but it looks like the key step is already out of our hands at ULT creation time so there isn't much a custom pool or scheduler could do. Thanks for hearing me out, and thanks in advance for feedback (even if it takes the form of "that's a silly idea" :) ). thanks, -Phil