Thanks Aaron, that's very informative. I was wondering if you could speak to some of the workloop-specific differences if possible. Why is dispatch_sync unsupported on workloops? And in the 'multiple serial queues targeting a single workloop' case, why is it noted that dispatch_sync is discouraged for 'performance reasons'? Do those same performance concerns not apply in other configurations where serial queues ultimately target another serial queue?

Thanks, filed FB21232935 for this.

Thanks, filed as FB21232935

Thanks, filed as FB21232935 edit: This duplicate comment brought to you by a UI error indicating the prior message could not be sent, and I should 'try again in a few minutes'.