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Resources for “Real-Time and Performance Improvements in the 2.6 Linux Kernel”

Issue 134

From Issue #134
June 2005

Apr 25, 2005  By William von Hagen
 in
Resources for the print article.

“Realfeel Test of the Preemptible Kernel Patch” by Andrew Webber: www.linuxjournal.com/article/6405

Real-Time Patches and Projects

2.4 Pre-emptible Linux Kernel Patch: kpreempt.sourceforge.net

2.6 Real-Time and Preemption Patch from Ingo Molnar: redhat.com/~mingo/realtime-preempt

MontaVista Real-Time Project: source.mvista.com/linux_2_6_RT.html

RTAI Project: www.rtai.org

DIAMPM RTAI (Real-Time Application Interface): www.aero.polimi.it/~rtai

Benchmarks

realfeel Benchmark: brain.mcmaster.ca/~hahn/realfeel.c

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Time interval

Anonymous's picture
Submitted by Anonymous (not verified) on Thu, 06/02/2005 - 17:28.

Figure 3 is reported as a 1 min. run time.

The end of the test period, around 3500, shows a increase in jitter. Has a longer than 1 min. run been tested? What do the results above 1 min. show?

Am I seeing a bug?

John Major's picture
Submitted by John Major (not verified) on Tue, 05/17/2005 - 00:59.

Great article. Clears up that nagging "I know this is good but how does it help?" I had about preemtable kernel. When I look at the jitter results in figure three I have two related questions. Why is the distribution so balanced in the vertical direction (rather than skewed mostly to the positive), and why are almost all the positive data points balanced almost exactly by a negative point. Could this be a bug in Realfeel where a 'delayed' interrupt incorrectly causes a successive accurate interrupt to be reported as 'early' by the same amount? You can also see a few points in figures one and two where they exceed the general noise.