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Tags: kernel   cpu   battery   cpu-frequency   temperature   conky  
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URL: https://unix.stackexchange.com/q/416954
Title: Which is better, High CPU % with Low Frequency or the opposite?
ID: /2018/01/14/Which-is-better_-High-CPU-_-with-Low-Frequency-or-the-opposite_
Created: January 14, 2018    Edited:  June 11, 2020
Upload: November 24, 2022    Layout:  post
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January 15, 2018 update

I created a 90 second Conky .gif showing “normal” behavior during start up:

Normal start-up .gif:

Conky startup.gif

Although this is under the same kernel 4.14.13 it doesn’t explain the abnormal behavior on January 13, 2018 when frequencies stayed in turbo-boost mode during the entire session.

January 14, 2018 update

I rebooted with Kernel 4.14.13 today and it is behaving like 4.14.12 yesterday. I can’t explain the difference and have no objections with this question be close voted.

High CPU % with Low Frequency vs. Low CPU % with High Frequency

Both these results are using FireFox with 10 tabs open in Non-Full Screen on laptop built-in 1080p display and FireFox with one tab open in Full Screen streaming a movie on External TV connected via ThunderBolt 3 USB-C to HDMI adapter. All tests were on a Skylake i7 6700HQ.

Kernel 4.14.12

All kernels sampled 4.4, 4.10 and 4.14 (up until version 4.14.13) exhibited High CPU % with Low Frequency.

CPU High Frequency Low.gif

Kernel 4.14.13

Whilst trying different kernels to watch Meltdown security hole impact I noticed an unrelated change where clock frequency was running at Turbo speeds constantly with a 10 degree increase in temperatures.

CPU Low Frequency High.gif

What Changed

The only difference is booting Kernel version 4.14.12 (High CPU, Low frequency) and kernel version 4.14.13 (Low CPU with High Frequency).

Ubuntu 16.04.3 LTS is used in both tests with no apt-get changes in-between.

In both tests the nVidia GTX 970M is disabled and only the Intel HD530 integrated graphics are used. When nVidia was activated on Kernel 4.14.4 the CPU % didn’t seem to decrease all that much but moving Windows on desktop wasn’t nearly as smooth as the Intel iGPU.

My other laptop has an Ivy Bridge 3630QM CPU and exhibits very different behavior in the three years I was using it. CPU % was slightly higher because it was a weaker processor but frequency would bounce between low and high all the time with most time spent in the middle. I think the frequency behavior was much preferable but, that is subjective. I’ll create some Conky .gif’s later for the 3630QM CPU if someone is interested.

Questions

Is it better to have Low CPU with High Frequency or High CPU and Low Frequency?

Battery use isn’t really a concern as this 17” laptop doesn’t go outside since it doesn’t fit into the coat pocket as easily as the 5.5” 1080p smartphone. It would still be good to know if Low CPU % or Low Frequency is better for battery life?

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