Robert Latham wrote:
On Fri, Mar 24, 2006 at 09:05:24AM +0100, Phil Carns wrote:
I'm not sure exactly which kernels from kernel.org are affected, but we
ran into a serious problem on the 2.6 kernel that we were using in RHEL4
(2.6.9-22.0.1.ELsmp). The symptoms occur during a write-heavy
workloads. From the PVFS2 point of view, write throughput on one or
more servers will slow to just a few KB/s, and the AIO thread will
consume 99% of cpu time.
Ugh. Thanks for tracking this down. I guess the only thing we can do
is add it to the FAQ?
That's all I know to do- I don't think there is any workaround we can
put in the PVFS2 code or anything.
David Metheny and I spent a long time tracking this down. I highly
recommend oprofile for debugging performance bugs like this. That was
what finally clued us in to where the problem was after a variety of
wrong turns :)
Glad to hear oprofile paid off!
I never set up a kernel before with the right modules to try it, but
RedHat is nice enough to put it in there by default on RHEL4.
-Phil
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