Messages in this thread | | | Date | Wed, 16 Jun 2004 17:45:51 +1000 | From | Nick Piggin <> | Subject | Re: PROBLEM: Heavy iowait on 2.6 kernels |
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Guy Van Sanden wrote: > My machine is heavily used for all kinds of file serving (mainly nfs), > but also samba. > Next to that, it is my home-server, so it runs apache2 (tuned to server > only few clients), imap (cyrus), postfix, bugzilla (mysql) and distcc > (used only a few times a week). > It replaces a FreeBSD system (PII-333) running the same except distcc. > Under > > The disk system is just a regular IDE disk (udma5) (60GB) and one > external drive over USB2 (160 GB). The external drive is rather slow > (20-30 MB/sec), so I disabled it during the tests. > > The weird thing is that I see this problem too when only running bonnie. > A friend of mine tried that too under 2.6.6, his iowait went up to > 0.15%, mine to 99%. >
The CPU can very easily max out the disks of course. If bonnie is doing IO to files much larger than memory, it wouldn't be surprising for io-wait to get close to 100%. Possibly your friend was doing all IO out of cache?
If you definitely have a performance problem, set "Kernel Debugging" on in the "Kernel Hacking" menu, then set "Magic SysRq key" on. When your system hits this iowait problem, press Alt+SysRq+T a couple of times over a few seconds.
Then post the output of `dmesg -s 1000000`.
We'll see what is waiting where. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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