OK; so we've got to be careful to keep the debug together; I think you really
have two separate things going on:
a) Slow when transferring lots of stuff (as per your vmstat in #9)
b) 'hang up's
Is that perf report from the 'hang up' state - it doesn't seem to have
much system/kernel CPU usage - so I'm assuming that perf report (#13)
corresponds to the vmstat in #12 - is that correct? (That perf doesn't
seem to show much doing anything - which again if it's that hang up
state when it's mostly idle/wait makes sense)
OK, so for (b) - have you got a dmesg from the server after a hangup?
The other thing I can suggest for (b) is to try reducing the 'dirty_ratio', it
causes the kernel to start to write out to disk sooner;
try (as root):
echo 2 > /proc/sys/vm/dirty_ratio
and see if that makes any difference to the hang up case.
Now, I think it's still worth investigating the (a) case - i.e. the high
cpu load when transferring a lot; if you can get a perf report for that
case it would be interesting to tie up.
Dave
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https://bugs.launchpad.net/bugs/1071978
Title:
nfs kernel server is very slow and causing high cpu load
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