stress-ng not reaching 100% CPU load

Question

I'm using stress-ng and not able to reach 100% cpu load. stress-ng, version 0.09.60 on kernel 4.1.35 a quad core ARM processor. I've used the following commands:

stress-ng --matrix 4 --tz --ignite-cpu

I noticed that the cpu climbs up in 25% increments to 75% when I use the following:

• stress-ng --matrix 1 --tz --ignite-cpu → 25% cpu load
• stress-ng --matrix 2 --tz --ignite-cpu → 50% cpu load
• stress-ng --matrix 3 --tz --ignite-cpu → 75% cpu load

Any higher matrix number of workers does not increase the load, for example

• stress-ng --matrix 10 --tz --ignite-cpu → 75% cpu load

I've also tried as referenced
stress-ng -c 4 -l 100 or stress-ng -c 0 -l 100 and it still doesn't go above 75%. In fact those --cpu-load options don't keep cpu up as consistently as --matrix option.

Answer 1

I wonder if you want to use dd to increase CPU benchmark. I usually use it to test CPU usage alarm.

dd if=/dev/zero of=/storage/test bs=1M count=1024 | md5sum

ref: How to use 'dd' to benchmark your disk or CPU?

Perhaps not many people use this, but 'dd' in conjunction with any stream-processing CPU-intensive program can also be used as a simple CPU benchmark! It may be not very accurate, but the huge advantage is that it doesn't require installing any additional software whatsoever, and typically you can run this “out of the box” on any GNU/Linux system.