[Dovecot] Very High Load on Dovecot 2 and Errors in mail.err.

Jesper Dahl Nyerup jesper at dahlnyerup.dk
Tue Jun 12 00:37:13 EEST 2012

On Jun 11  14:51, Timo Sirainen wrote:
> On 11.6.2012, at 11.09, Jesper Dahl Nyerup wrote:
> > In short, as far as we can tell, all the processes in D state appear to
> > be waiting to close the file handle they got from their inotify_init(),
> > and eventually all these close()s go through almost simultaneously.
> Yeah. Looks like a kernel bug. You could try if it goes away by disabling inotify in Dovecot. Either recompile with "configure --with-notify=none" or maybe you can disable inotify globally with:
> echo 0 > /proc/sys/fs/inotify/max_user_watches
> echo 0 > /proc/sys/fs/inotify/max_user_instances

I can confirm that this removes the symptoms, and that it doesn't affect
the service. Obviously IDLEing users are now only notified upon polling
of the file system, but the I/O overhead of doing this seems minimal.

It may be important to note, that even though load on our servers
surpass 2000, both Dovecot and the server as a whole is responsive and
servicing requests, up until the point where Dovecot reaches its
configured maximal number of child processes.

We're still chasing the root cause in the kernel or the VServer patch
set. We'll of course make sure to post our findings here, and I'd very
much appreciate to hear about other people's progress.

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