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

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On 01/11/11 11:19 -0500, ktm@xxxxxxxx wrote:
On Tue, Nov 01, 2011 at 12:14:28PM -0400, Mark London wrote:
ktm@xxxxxxxx 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?

Do not quote me, but there is a problem with the SASL spec and the
needs of the PAM stack that cause the leak and the only way to free the
space is to restart saslauthd.

More than likely a memory leak in saslauthd, when using the pam backend, is
caused by a bug in one of the pam modules being used. At least that's been
my experience.

Dan White

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