Re: sys cpu usage

[Michael Loftis <mloftis@modwest.com>]

--On August 26, 2008 6:48:35 PM +0300 blorb <shaharf@gmail.com> wrote:

> well, if it's within the mysql, try mytop but if it's something within
> the apahce or php i'm not sure myself...
> but try logging while working
>
> tail -f /var/log/whatever.log (change whatever to stuff you think making
> the troubles)

%sys is kernel CPU usage though.  mytop/etc can identify within that 
specific userspace app.  One can use strace and profiling utilities to 
profile userspace code runtime and the interface into the kernel, which can 
give you a better idea, but I don't know of any way to get function level 
profiling (time spent information) inside the kernel, just the strace 
information which shows you as you transition to/from kernel space for eg 
open, read, write, close, select, etc.

> Shahar Fermon.
>
>
>
> On Tue, Aug 26, 2008 at 6:18 PM, Michael Loftis <mloftis@modwest.com>
> wrote:
>
> It really depends on what you're doing and how.  Specifics about your
> configuration can make a world of difference.  On our web servers, where
> their primary filesystem is on NFS, the NICs do UDP/TCP checksum
> offloading, and they mostly push large packets I see up to about 15% or
> so on dual core 2Ghz processors (Xeon 5130s not hyperthreaded, so four
> CPUs). But that's peak, average is more like 7-8% at around 70
> hits/second, and we've a pretty high overhead too.  So 25%+ sounds off.
>
> As far as finding out where it's spending time, well, there aren't many
> options there with Linux.  Solaris has dtrace, and with that you can do
> profiling. OS/X has Shark and a couple others (and they're dtrace under
> the hood).  But I've never found a good way of profiling the Linux kernel.
>
> --On August 26, 2008 4:45:38 PM +0200 Marek Podmaka
> <marki@marki-online.net> wrote:
>
>
> Hello all,
>
> What is normal sys CPU usage in %? I have DualCore Xeon with
> hyperthreading, so 4 logical CPUs as reported by kernel (2.6.24.3),
> but the "sys" usage is about 25% (or 97% on scale when max is 400%).
> It grows proportionally with normal (user and nice) cpu usage, but
> seems too high for me. Server is running etch with php+mysql.
>
> Or is it normal? How can I see what causes it?
>
> Here is graph from munin: http://92.240.244.190/cpu-week.png
>
>
> --
>   bYE, Marki
>
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> Michael Loftis
> Modwest Operations Manager
> Powerful, Affordable Web Hosting
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Michael Loftis
Modwest Operations Manager
Powerful, Affordable Web Hosting