VILLASnode/doc/Tuning.md

Tuning

Operating System and Kernel

For minimum latency several kernel and driver settings can be optimized. A PREEMPT_RT patched Linux kernel is recommended. Precompiled kernels for Fedora can be found here: http://ccrma.stanford.edu/planetccrma/software/

1. Important: Tune overall system performance for real-time:

$ dnf install tuned-profiles-realtime
$ echo "realtime" > /etc/tuned/active_profile
$ echo "isolated_cpucores=6-7" >> /etc/tuned/realtime-variables.conf
$ systemctl enable tuned && systemctl start tuned

This enables the following tuned profiles: - latency-performance - network-latency - realtime

2. Map NIC IRQs => see setting affinity

3. Map Tasks => see setting affinity

4. Increase priority of server task (nice(2)) => see setting priority

5. Increase BSD socket priority => see setting priority and node-type socket

6. Configure NIC interrupt coalescence with ethtool:

$ ethtool -C|--coalesce devname [adaptive-rx on|off] [adaptive-tx on|off] ...

7. Configure NIC kernel driver in /etc/modprobe.d/e1000e.conf:

# More conservative interrupt throttling for better latency
# https://www.kernel.org/doc/Documentation/networking/e1000e.txt
option e1000e InterruptThrottleRate=

Hardware

This are some proposals for the selection of appropriate server hardware:

• Server-grade CPU: Intel Xeon

  • A multi-core systems allows parallization of send/receive paths.

• Server-grade network cards: Intel PRO/1000

  • These allow offloading of UDP checksumming to the hardware