Optimized Network Settings

23 09 2013

From RedHat Performance Tuning Guide:

Performance tuning is usually done in a pre-emptive fashion. Often, we adjust known variables before running an application or deploying a system. If the adjustment proves to be ineffective, we try adjusting other variables. The logic behind such thinking is that by default, the system is not operating at an optimal level of performance; as such, we think we need to adjust the system accordingly. In some cases, we do so via calculated guesses.

As mentioned earlier, the network stack is mostly self-optimizing. In addition, effectively tuning the network requires a thorough understanding not just of how the network stack works, but also of the specific system’s network resource requirements. Incorrect network performance configuration can actually lead to degraded performance.

For example, consider the bufferfloat problem. Increasing buffer queue depths results in TCP connections that have congestion windows larger than the link would otherwise allow (due to deep buffering). However, those connections also have huge RTT values since the frames spend so much time in-queue. This, in turn, actually results in sub-optimal output, as it would become impossible to detect congestion.

When it comes to network performance, it is advisable to keep the default settings unless a particular performance issue becomes apparent. Such issues include frame loss, significantly reduced throughput, and the like. Even then, the best solution is often one that results from meticulous study of the problem, rather than simply tuning settings upward (increasing buffer/queue lengths, reducing interrupt latency, etc).

https://access.redhat.com/site/documentation/Red_Hat_Enterprise_Linux/?locale=en-US

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