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System mode CPU time in Linux

Posted on 2009-07-09
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Last Modified: 2012-05-07
Hello Experts,
I am analyzing performance on a linux server and have noticed that a majority of the CPU time is allocated to system mode execution.  Normally (ie, in Windows for me), I would start to look at whether drivers are up to date, fragmentation was an issue, etc.   My question is - is there anything to tune on a Linux system that shows a high system to user mode execution ratio?  Or, is that just the way it is and I should look elsewhere for problems?
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Question by:markdolar
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by:mrjoltcola
ID: 24819686
system time represents time spent in system calls (kernel space) and/or IO.
user time represents time spent in actual user code.

Could be your system is doing a lot of IO.
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by:markdolar
ID: 24824378
Thank you for the comment.

Certainly high I/O is suspected, but the relatively low I/O wait time makes me suspect other contributors.  I'd like to follow the trail directly into system calls for some of the peaks, but I don't know how to make that connection.   Any assistance appreciated.
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mrjoltcola earned 500 total points
ID: 24824473
I would agree, there are other things besides IO that can register as system.

You can use strace to trace a given program / process.

You can also turn on system call auditing (google linux system auditing)


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