Thread context switches are about scheduling threads on physical cores. Async is about executing in a scope on a thread. There's no direct conversion here. Pack

Thread context switches are about scheduling threads on physical cores. Async is about executing in a scope on a thread. There's no direct conversion here. Packing a thread with async tasks could let you reduce the number of threads you have, which will probably reduce the thread context switching if there is contention for cores. Whether that's significantly better than the cost of async context switches really depends on specifics (even if async context switch cost is near zero, though we're no longer talking about C++ coroutines in that case). But keep in mind: If your threads are mostly waiting, they aren't triggering a lot of context switches. More async means fewer busier threads, less async means more less busy threads. To run into a problem with less async your threads need to be forcing switching at pretty fine-grained level. (BTW, most blocking for IO isn't fine-grained from the perspective of instructions executing on a core) That kind of thing happens, but has solutions other than async.