[AGENT++] SNMP v3 get performance

[Frank Fock]

Hi John,

I think adding localized users only will provide
best performance. As you know the user/passphrase
combination for all agents, you can localize them
with the agent's engine IDs and add them all to
the USM before you start polling. After that, you
do not need to modify the USM anymore.

Best regards,
Frank

John McCaskey wrote:
> Everyone,
> 
> Using the patch I previously provided for per session v3MP objects I have my
> polling engine running and stable using SNMP++ for all of our SNMP
> requests.  I have 80 threads that get spawned, each create's it's own v3MP
> object, and each checks a global queue for devices that need SNMP polling.
> Each thread then once it has a device sets up a new snmp session, which
> includes doing a usm->add_usm_user() call if the device is using v3, and
> then issues SNMP get requests on groups of OIDs until it has gathered all
> the data needed for the device.
> 
> This works well, but the performance when polling a large number of v3
> devices is pretty bad.  For v1 I can poll several thousand devices in a
> matter of a minute or two and performance is quite good on par with Net-SNMP
> which we used previously.  However, if I have just a couple hundred v3
> devices the performance starts to crawl.  Under my linux build I've been
> using oprofile to gather some performance data and it seems that the bulk of
> the time is being spent in the MD5 routines, I'm testing with a security
> level of authPriv using MD5/DES.  Here is the output from oprofile:
> 
> CPU: P4 / Xeon with 2 hyper-threads, speed 2592.35 MHz (estimated)
> Counted GLOBAL_POWER_EVENTS events (time during which processor is not
> stopped) with a unit mask of 0x01 (mandatory) count 100000
> samples % linenr info symbol name
> 9306146 64.4420 md5c.cpp:220 MD5Transform
> 3414196 23.6422 auth_priv.cpp:1040 AuthMD5::password_to_key(unsigned char
> const*, unsigned int, unsigned char const*, un
> signed int, unsigned char*, unsigned int*)
> 821898 5.6914 md5c.cpp:332 Decode
> 
> I'm interested in any suggestions on cutting down this time.  I know Jochen
> already mentioned that I shouldn't keep calling add_usm_user if the user has
> already been added previously, but given that each device may have any
> user/password combination and I have no way of knowing whether a device may
> use the same username as another, but have a different password I don't see
> how I can avoid that.  It seems like maybe what I need is for the table of
> added users inside snmp++ to be a little smarter and not lookup by just
> username but also by password so that whenever I add it will reuse if an
> exact match exists otherwise add the user again and perform the MD5
> computations again.  Does that seem like the best approach to improving
> performance?
> 
> John McCaskey
> Klir Technologies, Inc.
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