Re: can I measure IO per process?

On 02/14/2006 10:43:45 AM, Henry Poras wrote:
> > I'm currently running on RedHat AS3. On one of our boxes I noticed the CPU
> > was spending most of its time with 'wait io' (wa column in vmstat was
> > 85%-95%). The servicetime as seen from iostat -dk -x was also high, so
> > this was a problem. What I couldn't figure out, and what would be very
> > useful, was how to associate the io with specific processes. Is there a
> > way to do this?

Henry, Linux in general cannot do I/O request accounting. Linux is not a real Unix and lacks many good features and capabilities that are part of jAiX, HP-UX or Slowaris. One among them is the detailed I/O accounting. It can be done through a kernel patch. The tool that does it is called atop: http://www.atcomputing.nl/Tools/atop Of course, if you patch your RH kernel with anythig that doesn't come from Red Hat, your kernel is no longer supported. Linux is, actually, a fairly poor Unix with scheduler that is nowhere near as configurable as the one on SVR4, which doesn't have cfsadmin or anything similar to that for client side caching of the NFS file systems, doesn't have I/O accounting, it doesn't have many options to control virtual memory available to the users of real Unix systems and it has a bloated and enormous windowing environment called GNOME.

-- 
Mladen Gogala
http://www.mgogala.com



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