open vms buffered I/O and network performance on DS25 vs ES45

[kundu gangadharan]

Thanks for your thoughts. Appreciate your inputs.

Best Regards,
-Ganga

[Jon Pinkley]

kundu gangadharan,

Perhaps this has nothing to do with your issue, but since you specifically called out multicast traffic as being correlated to high processor utilization, I will ask.

Are all of the interfaces on the same network? If so, and each thread is binding to the same multicast group, then each interface will receive a copy of the same message. How does your application then handle duplicate received packets? If the same received packet is processed by multiple listeners, that could be causing contention for the shared memory.

Are the multiple interfaces intended for redundancy or for performance? The title mentions a DS25, but I don't see anything in the text mentioning it. Did you see better performance on the DS25? Were you expecting the application to scale linearly with additional processors?

Sorry that this doesn't answer any of your questions, but as others have stated, this is a reasonably complex problem, and there doesn't seem to be enough information here to diagnose it.

You stated your profiling showed that the time was on the interrupt stack. You may want to try and determine where the cpu time is being spent with something like the SDA PCS or PRF extension. If the time is being spent in the LAN driver's interrupt service routing, NICs that support Interrupt Coalescing (like the 3X-DEGXA-T* GBit NIC) could possibly help in bursty traffic situations.

Jon

[Rob Leadbeater]

Hi,

I can't offer much assistance in terms of the VMS side of things, however I'd also like to suggest that the NICs are likely to be the limiting factor here.

If you look at the supported options for the ES45 here:

http://h18002.www1.hp.com/alphaserver/options/ases45/ases45_options.html

you won't find the DE504. That's not say it doesn't work, but you might hit issues...

The tulip chips on the DE500s probably predate the ES45 by a good 10 years or so, so upgrading to something like the 3X-DEGXA-TR would seem a logical step.

Your original post mentions a DS25. That has a Gigabit interface on board. Does that have the same issue ?

A bit more information on the upstream switch arrangements and the other Linux systems might also be useful. Do the Linux boxes have Gb interfaces ?

Hope this helps,

Regards,

Rob

P.S. Do remember to assign points...