CPU Dependencies

[svilen888]

We have Superdome /PA-RISK/. Because of
bad application we need to upgrade CPU-cells.
At the beginning we have 16 CPUs, then we
upgrade to 20, now to 28 CPUs. But the improvement is not linear. So could anyone
explain the dependency between the CPUs /cells/ and the performance of the mashine.

[Karthik S S]

Refer to page no:2 - Cell population,

http://www.docs.hp.com/hpux/onlinedocs/2488/addon.pdf

Also,

http://www.docs.hp.com/hpux/onlinedocs/2489/upgradeguide.pdf

Hope this helps,

-Karthik S S

[Sanjiv Sharma_1]

Hi,

To achieve the best performance refer the Configuration Guidelines on page 149 of the Superdome Upgrade Guide.

http://docs.hp.com/hpux/onlinedocs/2489/upgradeguide.pdf

hth.

[Ted Buis]

In all multiprocessor systems performance doesn't scale linearily, but it depends on the application and configuration, particularily how much the CPUs are a factor in the application performance at all. Check your CPU utilization. If you are I/O bound then adding CPUs doesn't help. Superdome has even more concerns with scalability, since cell local memory is faster to access than memory in another cell. Memory access isn't uniform on Superdome. HP-UX 11i version 2 adds to HP-UX the ability to manage local memory usage versus off cell memory usuage, but that is only available for Integrity servers at this time. It may come out in a future release, but it may or may not help your application performance. I suggest that you really try to identify the bottlenecks in your system performance. You may find tine faster CPU would do better for you than more CPUs. You didn't mention your current clock rate, but there are new pa-8800 processor with dual cores, so you can get 8 CPUs per cell up to 1GHz. Again, these won't help if your fundamental bottleneck is I/O. As you add cells in Superdome you can add more I/O card cages which increase I/O bandwidth if needed.