Comment by vlovich123

I think you’re right but that’s basically my point. In practice glibc effectively ends up not freeing very much memory back to the OS. That’s the same as if it didn’t even bother releasing even though in theory it does have a code path to free.

The kernel does have techniques to try to free up that memory anyway (compressing them) but critically it’s not as effective as just letting the kernel know those pages are unused.