[Dovecot] Login process connection routing

[Timo Sirainen]

On Tue, 2010-07-20 at 09:57 -0700, Brandon Davidson wrote:
> Timo,
> 
> Just out of curiosity, how are incoming connections routed to login
> processes when run with:
> service imap-login { service_count = 0 }
> 
> I've been playing with this on our test director, and the process connection
> counts look somewhat unbalanced. I'm wondering if there are any performance
> issues with having a single process handle so many connections. It seems
> fine (system load is actually lower than with service_count = 1), but I
> thought I'd ask.

Dovecot lets kernel assign it. Whichever process grabs it first, handles
it.

> /usr/sbin/dovecot
>  \_ dovecot/imap-login
>  \_ dovecot/imap-login [1 connections (1 TLS)]
>  \_ dovecot/imap-login
>  \_ dovecot/imap-login [5 connections (5 TLS)]
>  \_ dovecot/imap-login [1 connections (1 TLS)]
>  \_ dovecot/imap-login [4 connections (4 TLS)]
>  \_ dovecot/imap-login [1 connections (1 TLS)]
>  \_ dovecot/imap-login [1 connections (1 TLS)]
>  \_ dovecot/imap-login [315 connections (315 TLS)]
>  \_ dovecot/imap-login [63 connections (63 TLS)]
>  \_ dovecot/imap-login [12 connections (12 TLS)]
>  \_ dovecot/imap-login
>  \_ dovecot/imap-login [10 connections (10 TLS)]
>  \_ dovecot/imap-login [2 connections (2 TLS)]
>  \_ dovecot/imap-login [370 connections (370 TLS)]
>  \_ dovecot/imap-login [24 connections (24 TLS)]

You probably have too many login processes. process_min_avail should be
set to about the same as the number of CPU cores. Since there are two
processes handling most of the connections, do you also happen to have 2
cores? :)