[Dovecot] What is normal CPU usage of dovecot imap?

[Mikko Lampikoski]

On 3.1.2012, at 17.12, Timo Sirainen wrote:

> On 3.1.2012, at 16.54, Mikko Lampikoski wrote:
> 
>> I got Dual Core Intel Xeon CPU 3.00GHz, over 1000 mailbox and almost 1 dovecot login / second (peak time).
>> Server stats says that load is continually over 2 and cpu usage is 60%. top says that imap is making this load.
> 
> You mean an actual "imap" process? Or more than one imap processes? Or something else, e.g. "imap-login" process? If there's one long running IMAP process eating CPU, it might have simply gone to an infinite loop, and upgrading could help.

It is "imap" process and process takes cpu like 10-30 seconds and then PID changes to another imap process (process also takes 10% of memory = 150MB).
Restarting dovecot does not help.

>> virtual users are in mysql database and mysqld is running on another server (this server is ok).
>> Do I need better CPU or is there something going on that I do not understand?
> 
> Your CPU usage should probably be closer to 0%.

I think so too, but I ran out of good ideas. If someone have lots of mails in mailbox can it make effect like this?

>> login_process_size: 128
>> login_processes_count: 10
>> login_max_processes_count: 2048
> 
> Switching to http://wiki2.dovecot.org/LoginProcess#High-performance_mode may be helpful.

This loses much of the security benefits, no thanks.

>> mail_nfs_storage: yes
> 
> Do you have more than one Dovecot server? This setting doesn't anyway work reliably. If you've only one server accessing mails, you can set this to "no".

Trying this too, but I think its not going to help..