On Tue, 27 May 2008 15:20:14 +0000 Andy Smith <andy@xxx.xxx.xxx> wrote: > Hi Al, > > On Tue, May 27, 2008 at 02:59:59PM +0100, Al Bennett wrote: > > As far as my basic understanding goes (please fill me in if I'm > > misunderstanding this!), iowait is when processes are waiting for > > the disks. > > Yes, waiting for IO in general, which is usually disk. > > > Looking at top doesn't really show me anything out of the > > ordinary and logs looks ok (which may well mean I'm not logging the > > problem...). > > > > What's the best way to find out what processes are waiting and what > > they're waiting for? > > It's tricky. On Linux, if you have a new enough kernel, you can use > iotop: > > http://guichaz.free.fr/iotop/ > > But other than that you are stuck with vmstat and iostat, which > don't show per-process results, only per block device. :( This sounds like something SystemTap (http://sourceware.org/systemtap/) might be able to help to solve. But of course until it's built in to every kernel it's not much use because you usually think to install these things after the problem has occurred :) -- Bruce - ---------------------------------------------------------------------- You can find the EdLUG mailing list FAQ list at: http://www.edlug.org.uk/list_faq.html
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