Linux-SRT

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Linux-SRT is no longer being actively maintained, sorry!

The project was very successful but is too complex to keep up to date, due to the time involved tracking the modified kernel, X-server and window manager.

I will leave these web pages up for reference though.

Linux-SRT is an extension to the Linux kernel which improves the way Real Time (RT) applications are run. Standard Linux isn't designed to be a "Media OS" and cannot guarantee that audio, visual or other critical processes run at a fixed rate. With RT tasks, predictability is even more important than simply running quickly.

Scheduling

This package helps solve the problem by letting you specify a desired Quality of Service (QOS) for real time applications. You can assign a certain percentage of the CPU to each task. This is more precise than the standard scheduler (which makes no guarantees) and more flexible than the all-or-nothing POSIX real time priorities.

Linux-SRT uses this rate-based control to ensure that multimedia applications run consistently without interruption. You can burn CDs and play mp3's without fear of glitches, regardless of the total load on the machine. You can also use it to put limits on the CPU consumed by particular processes, or to place background jobs in an "IDLE" scheduling class which defers to all others.

Graphics

The CPU assigned to a task is not the only factor affecting the speed of the application; in particular much depends on the shared X server process (for graphical applications). Linux-SRT overcomes this limitation with a simple extension to XFree86. This allows the X server to prioritize graphics rendering based on the scheduling parameters of each client.

User interface

Another practical problem with existing operating systems is that they lack convenient user-level tools for specifying scheduling parameters. Linux-SRT addresses this thoroughly with a GUI and automatic QOS management. These can be used to configure the normal Linux scheduling classes as well as the QOS extension.

In case you were wondering, the "SRT" moniker stands for "Soft Real Time". This basically means it's used for controlling multimedia applications and not for Space Shuttles or Nuclear Reactors (that would be Hard Real Time!)

Maintained by David Ingram (last updated 11 May 2000)
Send comments to dmi@uk.research.att.com