Saslauthd constantly increasing memory use, solved by enabling caching. Why?

[Mark London]

ktm at rice.edu wrote:
> On Tue, Nov 01, 2011 at 11:57:57AM -0400, Mark London wrote:
>   
>> Hi - On RHEL 6, with the latest updates, I have SASLAUTHD configured
>> to use PAM authentication.  I'm also running SSSD. U sing this
>> configuration, the SASLAUTHD processes would gradually increase
>> memory usage.  After running for several days, each process was
>> using up about 680M.  Are there any known memory leaks when using
>> PAM?  I've found posts on the web from people complaining about PAM
>> memory leaks, but am not sure they still exists.  In any event, I'm
>> also experiencing that about once a week, SASLAUTHD starts recording
>> time out errors when trying to contact SSSD, i.e.
>> "pam_sss(imap:auth): Request to sssd failed. Timer expired."   I
>> decided to enable SASLAUTHD caching with the -c flag, and was
>> surprised to discover that the SASLAUTHD processes no longer use up
>> significant memory (i.e. they are now using < 10M)!  Can anyone
>> explain this behavior?  Thanks. - Mark
>>     
> Each trip through the PAM stack loses some memory. When you turn on
> caching, you make a single trip for each authentication via SASL
> and then it uses the cached copy from then on. This bounds your
> memory use to N x num-users. Without caching, the growth as you
> found is unbounded.
>   

Thanks for the info!  But without caching, does the Mailman related 
memory use, eventually get freed up?

Also, are there any bad side effects from turning on caching?  If not, 
why isn't it the default?

- Mark