[conradludgate]

This is true. After I wrote my initial reply I did some measurements. After spawning 4096 threads on my M1 mac, I saw 80MB of reported memory usage. The equivalent tasks in tokio after spawning 100,000 of them reached only 100MB memory. This is roughly 20x less memory.

One common thought I see a lot though is that each thread uses 1MB (or more) in stack space alone. This just isn't true with modern memory paging