RHEL-RT HOWTO

From RHEL-RT

RHEL-RT HOWTO Introduction

The HOWTO is the primary documentation for MRG Realtime. Rather than writing an infinitely long documentation manual (that nobody would read anyways), we are instead composing a howto style writeup. It is intended to describe how to do performance monitoring / characterization of realtime systems, as well as specify tuning parameters. We will strive to use illustrative examples throughout.

In its current form, we have focused on content over formatting. So its not too pretty. We'd rather get the info out to interested users rather than sitting on it till its complete. This information is regularly being updated over time. Hence its a "living" document. Input and feedback are also welcome.

The main chore in getting deterministic realtime low-latency performance is proper tuning. There is so much diversity in workloads, that there truly is no one-size-fits-all maximum system tuning. While the Linux kernel strives to automatically perform dynamic tuning, there still remains much manual tuning required.

This HOWTO is organized into several sections which separate the tuning information based on:

• General system tuning - RHEL-RT GeneralSystemTuningHowto - these tunings are equally applicable to standard RHEL5 as they are to RHEL-RT. These same tunings are equally applicable when running the RHEL-RT kernel. Since many customers perform an apples-to-apples comparison of standard RHEL5 vs RHEL-RT the suggested approach is to first perform standard tunings and measure their impact on performance. The reason this is important is because the vast majority of deterministic improvement comes from the generic system tuning. If you don't successfully do this first, then simply dropping in a RHEL-RT kernel on an otherwise untuned RHEL5 system is unlikely to demonstrate realtime performance benefits.

• Realtime specific tuning - RHEL-RT RealtimeSystemTuningHowto - this section describes the new tuning options available in RHEL-RT which are not present in standard RHEL5.

• Application tuning & deployment - RHEL-RT ApplicationTuningHowto - recommendations for application developers to consider to achieve optimal determinism - to best capitalize on realtime features.