delay observed in pam_authenticate when called multiple times.

Hello Sir/Madam,
I am working on a PAM authentication module where i am seeing delay in pam_authenticate when called in sucessive manner.Below is my PAM function call sequence.
pam_start()
...
1. pam_authenticate()
2. pam_authenticate()
3. pam_authenticate()

4. pam_authenticate()

....

1000.pam_authenticate()
....
pam_end()

It is observed that the first pam_authenticate responds with 40 ms. The response time goes up with every subsequent pam_authenticate call. for 1000 the call the response time is observed to be 2 seconds.

Below are my system details:

[myuser@myhost workdir]$ ls -l /lib/libpam*
lrwxrwxrwx. 1 root root    17 Oct 18  2013 /lib/libpamc.so.0 -> libpamc.so.0.82.1
-rwxr-xr-x. 1 root root 13764 Oct 15  2012 /lib/libpamc.so.0.82.1
lrwxrwxrwx. 1 root root    21 Oct 18  2013 /lib/libpam_misc.so.0 -> libpam_misc.so.0.82.0
-rwxr-xr-x. 1 root root 11460 Oct 15  2012 /lib/libpam_misc.so.0.82.0
lrwxrwxrwx. 1 root root    16 Oct 18  2013 /lib/libpam.so.0 -> libpam.so.0.82.2
-rwxr-xr-x. 1 root root 52540 Oct 15  2012 /lib/libpam.so.0.82.2
[myuser@myhost workdir]$ uname -a
Linux myhost 2.6.32-358.18.1.el6.i686 #1 SMP Fri Aug 2 17:10:27 EDT 2013 i686 i686 i386 GNU/Linux
[myuser@myhost workdir]$ cat /etc/redhat-release
Red Hat Enterprise Linux Server release 6.4 (Santiago)

I have observed the same behavior on RHEL 6.2 as well. 
Thanks & Regards, 
MINAL PATIL

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