[Dovecot] Problems with the pop3 part of dovecot

[Timo Sirainen]

On Sun, 2008-10-26 at 09:57 -0700, Brandon Lamb wrote:
> basically I need to find out where to start looking to find out what
> is the problem with my dovecot pop3 setup. I switched from courier
> imap/pop3 to dovecot imap/pop3. I have had super high loads (40+ and
> overnight one server went to 511) and its been a nightmare fighting
> with this new setup for the last two weeks.
> 
> I did manage to narrow the problem down to it being with the pop3 part
> of dovecot. I am not sure why the load keeps going so high. 

Usually this is because Dovecot wants to calculate the messages' virtual
sizes. See maildir performance in http://wiki.dovecot.org/POP3Server.
There were also some issues with this where Dovecot didn't always add
the virtual size to dovecot-uidlist, but they were fixed in v1.1.5.

So the initial high loads are expected if your file names don't
contain ,W=size in them, but after that it should slow down. Of course
if your new messages don't contain ,W= in them either, the load is still
higher than it could be (but then again, Courier does the same thing so
it shouldn't be higher than with Courier).

One possibility would be to just make Dovecot violate POP3 spec and
return file sizes as message sizes. Some servers like qmail-pop3d do
that and they apparently work well enough.. This could be done by
changing mail_get_virtual_size to mail_get_physical_size in
src/pop3/client.c

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