This program starts N threads, and tries to loop as fast as possible in each thread. It reports how fast the loops are spinning relative to their best performance. You'd use it along with a workload that is suspected to use more compute resources than is reported by Linux.
I have to be honest, I don't remember where this program came from, or who the original author was. To the best of my recollection it was written by someone on LKML, in the early 2000s, and provided as proof that you can get away with running computation on Linux without it being accounted for in top/ps/etc. I have kept it around for ages making small enhancements and eventually put it in a git repo in 2023.
Build the program using make, there are no dependencies other than a standard
C development environment with posix threads.
You probably want to run as many busyboy threads as there are logical processors
in your system. It is further best to run busy boy with a low scheduling
priority, so that it does not impact the actual workload.
$ nice -n19 ./busyboy -n $(nproc)
all cpus started.
100 100 100 99.7 100 99 100 98.9 96.8 99.4 99.1 98.9 95.6 98.7 97.1 98.7
100 99.7 100 98.2 99.4 98.6 98.2 100 97.4 99.8 99.9 99.9 97.9 99.5 99.1 95.2
98.4 99.3 99.6 99 98.9 97.8 95.1 99.2 98.2 99.6 98.9 99.6 95.3 98.5 93.9 97.7
99.2 99.2 99.7 98.2 98.5 99 98 99.2 95.1 98.8 99.7 99.9 99.4 98 99.8 98.2
^C
A line is printed roughly every second, with how fast each thread was able to run as a percentage of the fastest we have observed to this point.
You can also run busyboy in summary mode:
$ nice -n19 ./busyboy -n $(nproc) -s
all cpus started.
0.000 97.053 100.000 97.098
87.127 95.374 100.000 95.427
83.851 96.019 99.176 96.086
94.614 97.068 98.371 97.073
^C
Each line shows: lowest score, mean score, max score, and standard deviation
The values could fall bellow 100% if:
- system is using CPU frequency scaling and clock cycle goes up and down
- other threads are using CPU cycles and not letting our busy boy run