Some quick notes on the code:

• The ClockTest.sh script compiles the code, and executes the test programs. It uses taskset to ensure that the tests don't migrate to different CPUs. (taskset is done only for the C++ test – the JVM uses so many threads that pinning them all to a single CPU is probably not a good idea). You'll need to modify the script to specify the correct location for JAVA_HOME on your system, or set JAVA_HOME prior to calling the script.

• The script detects whether the rdtscp instruction is available by querying /proc/cpuinfo. If not, it bypasses that code (which would otherwise throw a SIGILL).

• You can also pass in the CPU frequency, in GHz. If you don't, then a frequency of 1 is used, which has the effect of returning the tick count unmodified for those clock sources that use tick counts (i.e., anything having to do with the RDTSC instruction).

• If the script doesn't seem to be working, execute it with “bash -xv ClockTest.sh” to see the actual commands.

© Copyright 2014 by Bill Torpey. All Rights Reserved.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.