Tips to Reduce Processor Latency
For some of financial and data-acquisition applications, it's more important to finish one calculation super-fast than a bunch of calculations slightly slower. There's a group of HPC apps with a similar requirement: two identical instructions need to have precisely the same latency, every time they're executed.
Real-Time Operating Systems (RTOS) can help address these two scenarios. These OSes address latency in a number of ways; for example, by ditching device-polling and background cleanup tasks that that standard OS's normally do.
However, some features of modern industry-standard servers can hurt low- and consistant-latency computing. For example, low-power processor modes might save power, but any such processor throttling can increase latency. Another example would be management routines that consume CPU cycles, such as routines built into the BIOS of ProLiant server blades that occasionally use CPU cycles to track resource utilization and monitor correctable memory errors in the memory controller.
If you face these situations and have already gone with an RTOS, HP's got some settings in our RBSU (ROM BIOS Setup Utility) that can offer additional help.
Load up RBSU (accessed by pressing F9 while the system is booting), and change the following settings:
1) Set "ProLiant Power Regulator Mode" to "Static High Mode".
2) Disable processor c-state support.
3) If you are running an application that is single-threaded, set "Processor Core Disable" to "One Core Enabled".
4) On Intel Xeon 5500-based servers (like the BL460c G6), disable "QPI Power Management", and ensure "Intel Turbo Boost Technology" is set to "Enabled".
If you want to go even further, there's a way to disable some of those periodic BIOS checks on processor utilization and correctable errors. For most G5 and G6 server blades, HP has a tool called conrep (provided with the Smart Start Scripting Tool Kit) that let you control these settings.
In the BL280c G6, BL460c G6, and BL490c G6, you can also disable those things straight from RBSU. Hit "Control-A" within the RBSU, and some additional options will appear in the
"Service Options" menu.
