[Dovecot] Ongoing performance issues with 2.0.x

Stan Hoeppner stan at hardwarefreak.com
Sat Nov 6 17:28:06 EET 2010

Ralf Hildebrandt put forth on 11/6/2010 9:15 AM:
> * Stan Hoeppner <stan at hardwarefreak.com>:
>> What hardware platform? (AMD/Intel/SPARC/PPC, generation/freq)
> Intel(R) Xeon(R) CPU           L5335  @ 2.00GHz
>> What OS platform?
> Debian lenny 
>> What compiler/version?
> gcc version 4.4.5 (Debian 4.4.5-2) 

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

>> What threading library?
> ? how do I find out?

I was mainly asking that in case your platform was something other than
x86.  With Linux you should be using NPTL for threading.  This shouldn't
be a problem.

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?

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?

Is this a virtual machine guest or bare metal host?

What do memory and swap usage look like?

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?


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