Today I Learned

A Hashrocket project

Intel Speedstep and Ubuntu 14.04 Performance

Intel Speedstep works with the OS to adjust the clock speed of the CPU in real-time to save power. Older Linux kernels had a poor interaction with Speedstep that could cause the CPU to be downclocked even when running something demanding like a test suite. This can be fixed by disabling Speedstep in BIOS or upgrading the kernel. I was on kernel 3.13 and upgraded to 4.2. I saw 15-40% speed increase when running these tests.

Ubuntu 14.04.4 ships with a new kernel, but older installs of 14.04 will not be automatically upgraded. Run uname -a to see what kernel you are running. If it is not at least 4.2, then you may want to upgrade your kernel 1. Using aptitude this is simple as:

sudo aptitude install linux-generic-lts-wily

1 Upgrading the kernel in this way should be safe, but changing the kernel always has the potential to break something, so proceed at your own risk.