Replicating Java threading issues between machines with different cpu counts

Today I had a problem where a multi-threaded testcase which runs fine on my 8-core dev box failed when committed to the single-cpu build-server.

To replicate I needed to run on a single-cpu but I didn't want to commit more potentially broken tests to source-control and run repeatedly breaking builds on the build-server.

I discovered that its possible to bind an exec'd process to a single CPU in newer 'nix's using taskset. Invoking my maven build using taskset to bind the test-run to a single CPU core replicated the failure immediately, and from there it was an easy fix. Here's the cmdline to bind a maven build to a single CPU (I'm running Ubuntu, YMMV):

taskset -pc 0 mvn clean test

tasket is part of schedutils, which you may or may not have installed. It was installed on my machine already, possibly because of other things i've installed in the past. If needed you can install it with:

sudo apt-get install schedutils

It basically sets processor affinity by setting some process properties that tell the linux cpu scheduler to only allow the process to run on the stated CPU's.