[Dovecot] 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>
participants (2)
-
Joe Clark
-
Timo Sirainen