Comment by thamer

Redis is the kind of process where this matters a lot, and while fork() doesn't copy the memory, it still needs to copy the page table. For a process holding tens of GBs of RAM, fork() can take a long time, and there's one every time Redis dumps its .rdb file or rewrites its binary log ("AOF").

Even back in 2012 this blog post showed the high cost of this operation: https://redis.io/blog/testing-fork-time-on-awsxen-infrastruc...

On an m2.xlarge using ~25GB of RAM, fork() took 5.67 seconds. That's a long pause when Redis clients typically experience single-digit msec latency for most operations. Yes, that's only the time needed to copy the page table. It's surprising they don't mention huge pages, it seems like it would be a key consideration here.

No doubt hardware is faster 14 years later, but Redis instances likely use more RAM too. It'd be interesting to see this benchmark revisited.