[Dovecot] dovecot-auth Temporary But Frequent CPU Spike

[Timo Sirainen]

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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