[Dovecot] Dovecot waking every 50ms when doing nothing

[Ross Burton]

Hi,

My laptop runs a local IMAP server so that I'm immune from breaking my
mail client, and when playing around with powertop I discovered that
Dovecot (in particular imap-login) wakes up every 1000ms and then every
50ms even when no clients are connected.  A bit of stracing shows this:

gettimeofday({1180875699, 667917}, NULL) = 0 <0.000010>
poll([{fd=7, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=10, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=3, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=0, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=1, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}], 5, 999) = 0 <0.999595>
gettimeofday({1180875700, 667627}, {4294967236, 0}) = 0 <0.000007>
gettimeofday({1180875700, 667670}, NULL) = 0 <0.000007>
poll([{fd=7, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=10, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=3, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=0, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=1, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}], 5, 0) = 0 <0.000006>
gettimeofday({1180875700, 667762}, {4294967236, 0}) = 0 <0.000007>
gettimeofday({1180875700, 667801}, NULL) = 0 <0.000006>
poll([{fd=7, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=10, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=3, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=0, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=1, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}], 5, 999) = 0 <0.999699>
gettimeofday({1180875701, 667638}, {4294967236, 0}) = 0 <0.000010>

Is there any reason why dovecot wakes up so frequently even when there
is apparently nothing to do?  If it is to perform some routine task, can
this timeout be extended?  There are many daemons on my machine
(lighttpd is another) that are waking up every second when nothing is
happening, and each of these is contributing to waking the CPU from
sleep.

Cheers,
Ross
-- 
Ross Burton                                 mail: ross at burtonini.com
                                          jabber: ross at burtonini.com
                                     www: http://www.burtonini.com./
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