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c0m4r 08-19-2010 09:26 AM

Iowait indication

Is this possible to check which process or processess is responsible for high percent of iowait (%wa in top). I mean, I know that iowait measures CPU performance, not I/O but it depends directly on the hdd operations (f.e. copying). In other words I would like to check which process is generating hdd load.

Best regards,

quanta 08-19-2010 10:47 AM

As my understand, it may be:

ps -eo pid,user,state,command | awk '$3 ~ /D/ {print $0}'

c0m4r 08-19-2010 07:51 PM

This is exactly what I looked for and really good lecture to read. Thank you very much quanta.

syg00 08-19-2010 08:33 PM

So long as you only use it as an indication. As you said, this is really looking at things the wrong way around.
It is easy to construct situations where several tasks are "waiting" for I/O, but only one is contributing almost all the load. That can only really be checked by something like blktrace which is at the VFS layer.

Something else you might be interested in is iotop - very nice python script. Seems to be in most distros these days.

c0m4r 08-20-2010 10:24 AM

Yes. I know that what "ps" will show me with state "D" is not really what I am looking for, but it is already much more information than iowait alone gives me. Iotop seems to be exactly what I need, I'll check it. Thanks syg00.

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