[Dovecot] Ongoing performance issues with 2.0.x

[Ralf Hildebrandt]

* Stan Hoeppner <stan at hardwarefreak.com>:

> Hmm.  My Lenny systems have 4.3.2-2.  Are you maybe using Squeeze, not
> Lenny?

Yes, squeeze, sorry

> I'm still using i686 systems, but I wouldn't think that would change
> the version of GCC that gets installed.  I'm not sure if this may be
> playing a role in this problem or not.  What kernel version are you
> running, stock Debian or rolled from source?

2.6.32-23-generic-pae, from Ubuntu

> I'm trying to help you identify what is different on your system from
> other OPs that is causing 2.x to perform so badly vs 1.x.  If sys is
> high but usr and iowait aren't, then I would think the problem is in a
> system library, your kernel, dovecot, or more specifically, the
> interaction among all three.
> 
> You're using maildir correct?  What filesystem are you using?

Maildir on ext4

> Are you doing anything in your Dovecot config, both 1.x and 2.x, that is
> "unique" or non-standards maybe, compared to other OPs?

It's all users from /etc/passwd, but nothing special.

> Is this a virtual machine guest or bare metal host?

virtual machine guest
 
> What do memory and swap usage look like?

Memory usage is identical with 2.0 and 1.2:
total: 8GB
free: 5457MB
cached: 1054MB

The machine has no swap.

> What do you see for %CPU when you watch your kernel threads in top?  Is
> one of then eating lots of CPU time?  If so, which one?

Uhm, for that I'd have to switch back and look at kernel threads
explicitly.

-- 
Ralf Hildebrandt
  Geschäftsbereich IT | Abteilung Netzwerk
  Charité - Universitätsmedizin Berlin
  Campus Benjamin Franklin
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