On Tue, 2 Dec 2008, Daniel Pittman wrote:

> [EMAIL PROTECTED] writes:
>> On Mon, 1 Dec 2008, Aleksey Tsalolikhin wrote:
>>
>>> Hi.  I've got a Linux system that is spending more CPU time in system
>>> than in user.  sometimes more than double.
>>>
>>> I'd like to see what is the system call(s) that is chewing up the CPU.
>>>
>>> Is there any way to do that in Linux out of the box?   I am afraid the
>>> answer is no but I am hoping it's just a gap in my knowledge.   Are
>>> people using SystemTap?  I really don't want to install some
>>> expiremental kernel module...
>>
>> OProfile is one way to tell what system calls are being made. it's
>> part of the standard kernel (although your distro may or may not have
>> enabled it by default)
>
> I have, previously, found this very valuable.  It takes a bit of setup
> effort, but can apply across more or less anything, and gives good
> performance details.
>
> To my surprise, I have also found the 'powertop' tool to be valuable in
> finding out what is causing activity on the system, and reasoning from
> that about where that causes load.
>
> [...]
>
>> what's your disk activity like? that can eat a _lot_ of CPU time.
>
> My first guess was a PIO disk or similar, also.

software raid can also surprise you (especially if your distro is like 
debian and does a full raid re-sync at the beginning of the month)

David Lang
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