The queue is a single contention point which will have a considerable overhead unless the work takes a long time to execute (ie, enqueue is infrequent).

This kind of approach is usually not what you want: either you want to spawn threads as new work arrives (when each work unit is independent of each other), or you want to have a static number of threads each doing some predefined work (ideally one per core).

Scheduling pieces of work like this is going to be terrible for cache locality and will probably result in a number of threads waiting for each other and result in underutilization of the available cores.