dovecot - Dec 2008 - dovecot-auth Temporary But Frequent CPU Spike

Hi.. I am setting up a new server (2GHz CPU, Ubuntu 8.10) and am using 
dovecot for an IMAP server.  I have installed dovecot 1.1.4 and 
Squirrelmail 1.4.15.  sudo dovecot -n shows this:

# 1.1.4: /etc/dovecot/dovecot.conf
log_timestamp: %Y-%m-%d %H:%M:%S
protocols: imap
login_dir: /var/run/dovecot/login
login_executable: /usr/lib/dovecot/imap-login
login_process_per_connection: no
mail_privileged_group: mail
auth default:
  passdb:
    driver: pam
  userdb:
    driver: passwd

The problem I'm noticing is that if I do top -d 1 while clicking links 
in Squirrelmail (e.g., logging in, the Inbox link, opening a message), I 
see that a "dovecot-auth" process maximizes the CPU for about a
second.
While this is not a huge amount, it seems like with multiple users it 
could quickly bog down a server .

Are there any recommendations or thoughts on what might cause the 
one-second CPU spike?  -- or is that just normal operation?  Thanks for 
your thoughts.
- Joe Clark

On Tue, 2008-12-23 at 23:40 -0600, Joe Clark wrote:
> auth default:
>   passdb:
>     driver: pam
>   userdb:
>     driver: passwd
> 
> The problem I'm noticing is that if I do top -d 1 while clicking links 
> in Squirrelmail (e.g., logging in, the Inbox link, opening a message), I 
> see that a "dovecot-auth" process maximizes the CPU for about a
second.
"dovecot-auth", not "dovecot-auth -w"?
> Are there any recommendations or thoughts on what might cause the 
> one-second CPU spike?  -- or is that just normal operation?  Thanks for 
> your thoughts.
Probably the most helpful thing would be if you could hook gdb into the
dovecot-auth process:

gdb -p <pid>
cont

Then wait until the CPU hits high and then immediately get gdb
backtrace:

ctrl-c
bt full

Do this a couple of times and send the backtraces. They'll hopefully
show where it's waiting. Although if you see at the top that it's
waiting on poll() or epoll_wait(), then that doesn't really help. If you
can't get anything but those, try instead straceing the process and see
if it logs something useful:

strace -tt -p <pid>
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