VMA Tuning Parameters
Optimized performance can easily be measured by VMA predefined specification profile for latency:
It may limit the maximum bandwidth.
For blocking sockets only. It controls the number of times the ready packets can be polled on the RX path before they go to sleep (wait for interrupt in blocked mode). The recommended value for best latency is -1 (unlimited).
Controls which CPU core(s) the VMA internal thread is serviced on. The recommended configuration is to run VMA internal thread on a different core than the application but on the same NUMA node.
Binding VMA to the Closest NUMA
Check which NUMA is related to your interface.
The output above shows that your device is installed next to NUMA 1.
Check which CPU is related to the specific NUMA.
The output above shows that:
• CPUs 0-13 & 28-41 are related to NUMA 0• CPUs 14-27 & 42-55 are related to NUMA 1
Since we want to use NUMA 1, one of the following CPUs should be used: 14-27 & 42-55
Use the "taskset" command to run the VMA process on a specific CPU.
• Server side:
• Client side:
In this example, we use CPU 15 that belongs to NUMA 1. You can also use "numactl - -hardware".
Configuring the BIOS
Each machine has its own BIOS parameters. It is important to implement any server manufacturer and Linux distribution tuning recommendations for lowest latency.
When configuring the BIOS, please pay attention to the following:
- Enable Max performance mode.
- Enable Turbo mode.
- Power modes – disable C-states and P-states, do not let the CPU sleep on idle.
- Hyperthreading – there is no right answer if you should have it ON or OFF.
• ON means more CPU to handle kernel tasks, so the amortized cost will be smaller for each CPU
• OFF means do not share cache with other CPUs, so cache utilization is better
If all of your system jitter is under control, it is recommended to turn is OFF, if not keep it ON.
- Disable SMI interrupts.
Look for "Processor Power and Utilization Monitoring" and "Memory Pre-Failure Notification" SMIs.
The OS is not aware of these interrupts, so the only way you might be able to notice them is by reading the CPU msr register.
Please make sure to carefully read your vendor BIOS tuning guide as the configuration options differ per vendor.