Linux: One cpu core is always in 0 use

Question

Today I notice a very strange thing. One cpu core is always in 0 use .

Is it a bug?

Cpu0  :  0.0%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,100.0%si,  0.0%st
Cpu1  : 37.7%us, 44.4%sy,  0.0%ni, 13.9%id,  2.6%wa,  0.0%hi,  1.3%si,  0.0%st
Cpu2  : 56.0%us, 17.9%sy,  0.0%ni, 13.6%id, 12.3%wa,  0.0%hi,  0.3%si,  0.0%st
Cpu3  : 43.0%us, 40.4%sy,  0.0%ni, 13.2%id,  3.0%wa,  0.0%hi,  0.3%si,  0.0%st
Cpu4  : 45.4%us, 13.9%sy,  0.0%ni, 29.8%id, 10.9%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu5  : 32.3%us, 47.5%sy,  0.0%ni, 16.8%id,  3.0%wa,  0.0%hi,  0.3%si,  0.0%st
Cpu6  : 69.0%us, 12.5%sy,  0.0%ni, 15.8%id,  2.3%wa,  0.0%hi,  0.3%si,  0.0%st
Cpu7  : 38.1%us, 42.4%sy,  0.0%ni, 18.2%id,  1.3%wa,  0.0%hi,  0.0%si,  0.0%st

Are you running a single threaded program which is using that CPU? — Hennes, Dec 02 '12 at 19:00
I'm not sure which one can use a single cpu cure. I have mysql percona, nginx, apache, php — teslasimus, Dec 02 '12 at 19:06
What OS/kernel/distro? Do you have the irqbalance daemon running? That may impact this. Is this system physical or virtual? — ewwhite, Dec 02 '12 at 19:50

score 11 · Accepted Answer · answered Dec 02 '12 at 19:30

11

I don't see an idle CPU core in your output.

Core 0 is 100% active servicing software interrupts, all the others are split between user/system and idle.

answered Dec 02 '12 at 19:30

user9517

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how can i find what software uses only one cpu? – teslasimus Dec 02 '12 at 19:43
@teslasimus: That should be the subject of a new question. – user9517 Dec 02 '12 at 20:13

score 7 · Answer 2 · answered Dec 02 '12 at 19:29

7

That CPU isn't idle, if that's what you're thinking.

100.0%si shows that it's spending its time on handling interrupts.

answered Dec 02 '12 at 19:29

Shane Madden

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score 1 · Answer 3 · answered Feb 22 '14 at 14:00

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I know this is a old thread or this will answer your question but you can use

ps mo comm,psr

this will help you to find out in which processor the process is currently assigned to

answered Feb 22 '14 at 14:00

Prashant Lakhera

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Linux: One cpu core is always in 0 use

3 Answers3