Unix Fork Performance

Discussions center on the performance issues of fork() and fork/exec in Unix-like systems, particularly copy-on-write overhead for large processes, and alternatives like posix_spawn, vfork, and Windows CreateProcess.

📉 Falling 0.3x DevOps & Infrastructure
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Keywords

COW PHP IMHO GC DBAPI CreateProcess GDB OS github.com UNIX fork exec forking process cow processes child memory gc copy

Sample Comments

andreasvc Sep 7, 2013 View on HN

It's mostly about copy-on-write memory due to forks.

LgWoodenBadger Mar 23, 2023 View on HN

What else is there besides fork/exec?

evilotto Mar 22, 2023 View on HN

Is basic fork/exec from a large process still slow or have newer apis fixed that?

blibble Jan 29, 2013 View on HN

it's like a really really really expensive version of fork()!

brooksbp Dec 7, 2012 View on HN

Seems like more overhead than fork & execv technique.

justincormack Jan 18, 2016 View on HN

Use posix_spawn not fork and exec, then at least the OS may not allocate twice the memory, eg the BSDs will not.

ithkuil Jul 10, 2021 View on HN

Wasn't vfork designed to solve this issue? Does it not work in practice?

guenthert Nov 13, 2020 View on HN

You wouldn't fork() for performance, but for security reasons.

brcmthrowaway Aug 14, 2025 View on HN

What about OSes that dont use fork()?

knightoffaith Feb 20, 2024 View on HN

Could you educate me on what's wrong with fork()?