mailboxes.db locking problem after updating from 2.4 to 2.5.9

[Wolfgang Breyha]

On 18/11/16 01:07, Bron Gondwana via Info-cyrus wrote:
> On Fri, 18 Nov 2016, at 10:51, Wolfgang Breyha via Info-cyrus wrote:
>> I already filed a bug https://github.com/cyrusimap/cyrus-imapd/issues/43 
>> but no response so far. I directly asked Bron, but no response as well.
> 
> Sorry, I really don't have a clue.  2.5 does have a different mailboxes.db
> format, so it's a bit more CPU intensive.  The real massive win for CPU
> usage is going to come with reverse ACLs:

Thanks for the response in the first place! I'm sorry to push this topic
continuously because I appreciate all your hard work (and Ellies as well) on
cyrus very much!

We had a quite hard time keeping our infrastructure operational after doing
the final step upgrading our frontends to 2.5. Seeing others having the same
stress should be quite a warning for people thinking about an upgrade.

Since Deniss has these troubles with skiplist as well on 2.5 it looks like the
size
triggers it. twoskip seems to perform even worse if mailboxes.db reaches a
certain size,
or it's only the size penalty which hits twoskip earlier.
150-200 MB seems critical for locking issues.

> https://blog.fastmail.com/2015/12/05/reverse-acls-making-imap-list-fast/

I read about them some time ago in the 3.0.0-beta changelog. Hopefully we're
on a stable cyrus release supporting it before reaching the critical size for
skiplist;-)

> But to get there, we need to solve reverse ACLs for groups.  I did ask about it here:
> 
> https://lists.andrew.cmu.edu/pipermail/info-cyrus/2015-November/038628.html

Sorry, we don't use groups.

> But then didn't follow up to add group reverse ACL support in Cyrus, so reverse ACLs are broken if you're using groups.

So, 2.5 wont get them anyway I guess;-)

Greetings, Wolfgang
-- 
Wolfgang Breyha <wbreyha at gmx.net> | http://www.blafasel.at/
Vienna University Computer Center | Austria