Dovecot unresponsive at about 10,000 process

luck

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May 24, 2011
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Hello,
dovecot version 2.1, Freebsd.
At about 10000 process in the system it starts to beeing unresponsive all the operations takes forver with load getting >8.
- the CPU is 30% iddle, 25% free RAM,
- i do not connect this problem with NFS - no correlation between i/o and the slow down,
- indexes are on local SSDs
- no process limits has been hit - not in dovecot nor in the system itself

After a dovecot restart the problems are gone immediatelly - by the time the process number grow back to 10000 again which usually takes place quite fast in rush hours.

Any advice?

Thank you!
 
Well, it does hit a limit somewhere or you wouldn't ask the question :)

I would guess the slowing down is IO bound. The processes normally don't use much resources, but do use a lot of disk io. So you might benefit from some tips over here: http://wiki.dovecot.org/PerformanceTuning
 
Well, it does hit a limit somewhere or you wouldn't ask the question :)

I would guess the slowing down is IO bound. The processes normally don't use much resources, but do use a lot of disk io. So you might benefit from some tips over here: http://wiki.dovecot.org/PerformanceTuning


I've considered that but wouldnt the IO be the bottlenect all the same, after the dovecot restart? Like I mentioned - after the restart it works fine with the very same traffic.
 
I've considered that but wouldnt the IO be the bottlenect all the same, after the dovecot restart? Like I mentioned - after the restart it works fine with the very same traffic.

If you restart dovecot it has only a few processes running. But within a minute most of the disconnected clients start reconnecting automatically and dovecot will need increasingly more resources after a while.
 
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