How to speed up compilation time in linux

Question

While compiling under linux I use flag -j16 as i have 16 cores. I am just wondering if it makes any sense to use sth like -j32. Actually this is a quesiton about scheduling

Answer 1

I use a non-recursive build system based on GNU make and I was wondering how well it scales.

I ran benchmarks on a 6-core Intel CPU with hyper-threading. I measured compile times using -j1 to -j20. For each -j option make ran three times and the shortest time was recorded. Using -j9 results in shortest compile time, 11% better than -j6.

In other words, hyper-threading does help a little, and an optimal formula for Intel processors with hyper-threading is number_of_cores * 1.5:

Chart data is here.