Not worried, just curious: I'm currently running Handbrake 1.10 on my new Dell Inspiron 3576 with Bionic 18.04, and I see that all cores are working nice and hard. :) However, with all 8 virtual cores going (it's an I5 with 4 physical and 8 virtual cores) I see that all cores have pretty much the same load (which is as it should be) but the load of each core doesn't exceed 90% (give or take a few tenth of a percent). On occasion I have seen a single core max out to 100% for a number of seconds (not unusual) but now that all 8 cores are equally engaged, the load appears to be subject to a 90% limit.

Is this by design? If so, would that be a Linux feature, a Handbrake feature, or a property of the hardware?

It makes sense not to max out all cores completely (both in terms of keeping the system responsive and not frying the hardware) but I haven't seen this yet (not having run this version of Ubuntu and not having had recent and decent hardware until now) so I'm wondering what it is that I'm seeing here.

  • It is not by design. you should be able to max out all CPUs at 100% if you want to. May 27, 2018 at 15:17
  • If this is not a feature, then it would seem something else (memory or disk I/O perhaps) is the bottleneck here, which makes the ghb pocess not quite CPU bound. May 27, 2018 at 16:03

1 Answer 1


To test CPU capability outside of handbrake, you can force CPUs to 100%. Below are the steps from this answer: How do I stress test CPU and RAM (at the same time)?.

You can install stress with:

sudo apt install stress

Then call it with:

stress --cpu 8 --io 4 --vm 4 --vm-bytes 1024M --timeout 10s

On my conky display notice how:

  • In the top section CPU utilization spikes from 3% to 100%
  • In the middle the temperature spikes from 60C to 80C
  • At the bottom memory spikes from normal 2.75 GiB to 6.25 GiB

stress test.gif

Type stress --help for a full list of options.

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