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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
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  • 1
    Are you running a single threaded program which is using that CPU?
    – Hennes
    Dec 2, 2012 at 19:00
  • I'm not sure which one can use a single cpu cure. I have mysql percona, nginx, apache, php
    – teslasimus
    Dec 2, 2012 at 19:06
  • Try top to see if there is a process with 100% CPU time.
    – Hennes
    Dec 2, 2012 at 19:17
  • top process has nothing to do with my question.
    – teslasimus
    Dec 2, 2012 at 19:22
  • What OS/kernel/distro? Do you have the irqbalance daemon running? That may impact this. Is this system physical or virtual?
    – ewwhite
    Dec 2, 2012 at 19:50

3 Answers 3

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.

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  • how can i find what software uses only one cpu?
    – teslasimus
    Dec 2, 2012 at 19:43
  • @teslasimus: That should be the subject of a new question.
    – user9517
    Dec 2, 2012 at 20:13
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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.

1

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

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