kqueue is BSD-specific feature, so you can't use it with Linux.
Ah, I see now.
But I'd like to know what exactly does "stale processes" mean: Do you use SSL and they're all SSL connections?
Yes, they could all be SSL connections. Many certainly are, not sure if -all- of the stale ones are yet.
Are they eating any CPU at all?
top reports 0% CPU.
If you strace them, does it show if they're doing anything?
Just polling...
gettimeofday({1154640050, 545868}, {300, 0}) = 0 gettimeofday({1154640050, 546099}, NULL) = 0 poll([{fd=6, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=2, events=POLLERR|POLLHUP|POLLNVAL}, {fd=5, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=0, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}], 4, 0) = 0 gettimeofday({1154640050, 546512}, {300, 0}) = 0 gettimeofday({1154640050, 546725}, NULL) = 0 poll([{fd=6, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=2, events=POLLERR|POLLHUP|POLLNVAL}, {fd=5, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=0, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}], 4, 531) = 0
...and so on.
How long are they stuck, or don't they ever die?
Until I kill them manually.
How exactly do you know they are stale?
Because the clients have been closed and the user owning the process does not have any mail applications open.
Are you sure there aren't any clients that still have active connections to it?
Pretty sure - of course it could be the client shutting down uncleanly. Mostly 1.5.0.x of Thunderbird and squirrelmail-1.4.6-5.fc5 with an occasional pine user.
The symptom for me is either user's IMAP operation times out or just user slowdown. The resolution is that once I kill the old processes owned by that user, their performance immediately improves. Typical example is that user is trying to delete a message from the INBOX (i.e. move a message from INBOX to Trash in our Maildir environment). Thunderbird will just hang on it, or take 1 minute+ to move the message. If I kill the old imap processes, it seems that the move happens very quickly (~ 1 second) if the user tries again immediately thereafter.
-Fran
-- Fran Fabrizio Senior Systems Analyst Department of Computer and Information Sciences University of Alabama at Birmingham http://www.cis.uab.edu/ 205.934.0653