Re: High load average on disk I/O on 2.6.17-rc3
From: Robert Hancock
Date: Sat May 06 2006 - 13:22:14 EST
Jason Schoonover wrote:
There are, this is the relevant output of the process list:
4659 pts/6 Ss 0:00 -bash
4671 pts/5 R+ 0:12 cp -a test-dir/ new-test
4676 ? D 0:00 [pdflush]
4679 ? D 0:00 [pdflush]
4687 pts/4 D+ 0:01 hdparm -t /dev/sda
4688 ? D 0:00 [pdflush]
4690 ? D 0:00 [pdflush]
4692 ? D 0:00 [pdflush]
This was when I was copying a directory and then doing a performance test with
hdparm in a separate shell. The hdparm process was in [D+] state and
basically waited until the cp was finished. During the whole thing there
were up to 5 pdflush processes in [D] state.
The 5 minute load average hit 8.90 during this test.
Does that help?
Well, it obviously explains why the load average is high, those D state
processes all count in the load average. It may be sort of a cosmetic
issue, since they're not actually using any CPU, but it's still a bit
unusual. For one thing, not sure why there are that many of them?
You could try enabling the SysRq triggers (if they're not already in
your kernel/distro) and doing Alt-SysRq-T which will dump the kernel
stack of all processes, that should show where exactly in the kernel
those pdflush processes are blocked..
Robert Hancock Saskatoon, SK, Canada
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