Linux Webserver - htop shows extreme cpu usage?

Question

I am a bit confused about what the tool "htop" shows as cpu usage and average load. I was asked to have a look at a webserver which is performing incredibly slow. I googled a bit and always found the statement that everyting above 1.00 in average load is terrible when you only have one cpu in the machine.

However, my "htop" experience looks like this: htop screenshot

Can someone please tell me what exactly is going on here? Is this bad or do I misunderstand everything?

Thank you for your help.

score 1 · Answer 1 · answered May 23 '17 at 08:22

1

The htop screenshot is showing you each of the cores of the CPU and the usage for each. What you really want to be looking at are the processes and how much CPU they are consuming.

There's an article here which explains it in more detail: http://www.thegeekstuff.com/2011/09/linux-htop-examples

Goodluck!

answered May 23 '17 at 08:22

Erbilacx

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That's an interesting article. Thanks for that! – hallleron May 23 '17 at 08:40

score 1 · Accepted Answer · answered May 23 '17 at 08:35

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In your screenshot the CPU usage bars are colored in green and red. Press '?' in htop for a help screen to show up. From there you will see that green color is for a normal priority userspace applications CPU usage and the red color is for kernel threads.

Basically, in your screenshot all the CPU cores are 100% busy and most of the time they spend in the kernel.

Yes, this is bad. Further investigation is needed to tell what exactly is going on here.

answered May 23 '17 at 08:35

Andriy Berestovskyy

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Found it! There was a zombie like rsync script running which created hundreds of threads, all lasting for days... I killed the script and all threads, cpu usage went down now to 0.3% and the web server runs smooth again. Thank you for the explanation though. – hallleron May 23 '17 at 08:39

Linux Webserver - htop shows extreme cpu usage?

2 Answers2