Hacker News Reader

Instruction cache. If your mega binary doesn't fit into cache, instructions jump around to different and unpredictable address spaces. You are fetching and executing instructions directly from memory. This is why huge applications are so slow, they are both instruction memory bound and data memory bound. Imagine how slow a CPU is with no cache!

View on HN

Not all the instructions for modules have to be loaded into the instruction cache, that can easily be prevented with runtime config.

My original post was bourne out of frustration with nginx not having nginx_http_perl_module out of the box. If it's never loaded in the config file though, it never has to be loaded into memory at runtime.

A ryzen 2300X has 256KB of instruction cache, that's 4x64 KiB 4-way set associative. How can you hope to fill that?

I've personally ran gentoo on a 4.2GHz i3-530 as well as a 4.5GHz FX-4350. From kernel to firefox, I only gained performance going from -O2 to -Ofast. I have no hopes of considerable cache misses on a modern CPU.

Remember that your process is not the only one running on the CPU or core. Most of the time, at least, and even if it is via some artifice you get to call kernel code for syscalls and C library too.

Reply on news.ycombinator.com