Memory leak or misconfiguration: Repeated allocation of very large block

[Timo Sirainen]

On 24 Oct 2015, at 14:59, Sebastian Wolfgarten <sebastian at wolfgarten.com> wrote:
> 
> Dear all,
> 
> I am using Dovecot 2.2.19 and I keep on getting the following warnings in my mail.log file on FreeBSD 10:
> 
> Oct 24 10:45:28 server1 dovecot: imap: Error: GC Warning: Repeated allocation of very large block (appr. size 20480):
> Oct 24 10:45:28 server1 dovecot: imap: Error: 	May lead to memory leak and poor performance.
> 
> I am wondering whether this is a configuration issue (i.e. a mistake in my current config) or whether I am hitting a bug. What’s the best way of figuring this one out? I tried increasing the verbosity of the logs but it did not really provide me with further information.

I guess you have configured Dovecot --with-gc? I guess it's possible this is a bug, but it could just as well be a false alarm. In general I don't recommend/support --with-gc option (and I should probably just remove it altogether). The easiest and the most usable way of finding memory leaks is to run with valgrind (which must be done without-gc):

service imap {
  executable = /usr/bin/valgrind -q --show-reachable=yes --leak-check=full /usr/libexec/dovecot/imap
}

I'm not aware of any memory leaks right now.