HP B- Accelerators Linux manual Setting Numa affinity, Setting the interrupt handler affinity

Setting NUMA affinity

Servers with a NUMA (Non-Uniform Memory Access) architecture require special installation instructions in order to maximize ioMemory device performance. These servers include the HP ProLiant DL580 and HP DL980 Servers.

On servers with NUMA architecture, during system boot, the BIOS on some systems will not distribute PCIe slots evenly among the NUMA nodes. Each NUMA node contains multiple CPUs. This imbalanced distribution means that, during high workloads, half or more of the CPUs might remain idle while the rest are 100% utilized. To prevent this imbalance, you must manually assign IO Accelerator devices equally among the available NUMA nodes.

For information on setting NUMA affinity, see "NUMA configuration (on page 57)."

Setting the interrupt handler affinity

Device latency can be affected by placement of interrupts on NUMA systems. HP recommends placing interrupts for a given device on the same NUMA socket that the application is issuing I/O from. If the CPUs on this socket are overwhelmed with user application tasks, in some cases it might benefit performance to move the interrupts to a remote socket to help load balance the system.

Many operating systems will attempt to dynamically place interrupts for you and generally make good decisions. Hand tuning interrupt placement is an advanced option that requires profiling of application performance on any given hardware. For information on how to pin interrupts for a given device to specific CPUs, see your operating system documentation.

Performance and tuning 56