Dovecot unresponsive at about 10,000 process

luck

Verified User
Joined
May 24, 2011
Messages
30
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!
 

sysdev

Verified User
Joined
Jul 16, 2007
Messages
178
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
 

luck

Verified User
Joined
May 24, 2011
Messages
30
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.
 

sysdev

Verified User
Joined
Jul 16, 2007
Messages
178
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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