[Dovecot] Degeneration of CPU Performance

[Thiago Monaco Papageorgiou]

Hello everybody!

    We have a interesting issue about dovecot behavior here. First, the 
scenario:
    We have 2 server running with the same load, one with our old pop3 
solution (out of date) and other with Dovecot. We realized that dovecot 
are comsuming more CPU, and this consumption is growing day by day. When 
we starts dovecot, it runs between 40%-45% of CPU consumption and our 
old solution runs on 30-35%. This is quite acceptable, so no problem 
here. The problem is one day after it jumps to 45%-55% of cpu 
comsunption while the old pop3 solution runs on the same CPU consumption 
of one day before (30%-35). I attached a graph with this information.

In this graph the green line is dovecot CPU consumption and the blue 
line is the old solution.

In this graph we restart dovecot at monday morning. This restart is 
noticed as a big fall of CPU consumption(green line) in the graph. After 
that, it stay between 40%-45%, one day after it runs on 45%-55% and next 
day, it reaches 50%-60%! You can notice that the blue line (old pop3 
solution) runs with the same behavior, so we have the same load. We have 
other monitoring informations that confirm it.

I looked for some bugs about this, but I didn't find anything. The 
question is:
Is there any dovecot problem or wrong configuration that could cause 
this degeneration of CPU performance? Any sugestion about what can be 
the cause of this?

I attached dovecot -n output. Two important information: we store the 
mailboxes in NFS and we are only using pop3 protocol.


Thanks in advance!

-- 
Thiago Monaco Papageorgiou <thiago.monaco at corp.terra.com.br>
________________________
Terra Networks Brasil S/A 
Tel: +55 (51) 3284-4274

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