[karavelov]

It matters actually, if your each tasks use 10KiB stack for execution, and you have 1000 tasks, with threads that will consume 12MiB just for the stacks (+2KiB per task due to page alignment). If you use async runtime as Tokio the stack is un-rolled on each suspend point. So if you have 16 worker threads, that means the stacks will consume 192 KiB.

[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