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

[ktm at rice.edu]

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.

Regards,
Ken