[Dovecot] load increase after upgrade to 2.0.8

[Timo Sirainen]

On Thu, 2010-12-09 at 10:18 -0800, Mark Moseley wrote:

> Upping the client_limit actually results in less processes, since a
> single process can service up to #client_limit connections. When I
> bumped up the client_limit for imap, my context switches plummeted.
> Though as Timo pointed out on another thread the other day when I was
> asking about this, when that proc blocks on I/O, it's blocking all the
> connections that the process is servicing.

Yeah. And it's even worse if it's blocking on waiting for a lock.

BTW. Do you have these kind of error messages in your log:

net_connect_unix(pop3) failed: Resource temporarily unavailable
net_connect_unix(imap) failed: Resource temporarily unavailable

I think those are sometimes happening when not using client_limit=1,
because all the processes are busy at that time and can't accept a new
connection (while with client_limit=1 a new process would be created to
handle it).