Gutsy Gibbon's "-rt" kernel


EMC2's Latency-test on 2.6.22-12-rt
There's a new kind of realtime on the block, called 'CONFIG_PREEMPT_RT'. Gutsy Gibbon beta includes a version of this kernel, 2.6.22-12-rt. I decided to give it a try.

The "port" consists of changing sim_rtapi to use a mostly-pthreads API instead of pth, making it setuid, and making it able to do I/O.

latency-test 500us - reports latencies of up to about 32uS on a period of 500uS, and a scope on the parport confirms it.

This is promising for machines with only a servo-thread, but discouraging for software step generation.

To try it out, install gutsy beta and kernel 2.6.22-12-rt. Patch the TRUNK of emc with the patches below, and configure with --enable-simulator --enable-run-in-place. The "sudo make setuid" step is now required, and the "sim" name becomes increasingly inaccurate.

Since rtai offers a "mostly posix API" called lxrt, these changes also offer a way forward if the kernel-mode rtai APIs start to bitrot.

Files currently attached to this page:

0002-userspace-realtime-on-my-test-system-with-gutsy-k.patch22.0kB
0005-make-hal_parport-able-to-run.patch11.3kB
0006-make-most-drivers-compile-but-they-may-not-load.patch16.3kB


(originally posted on the AXIS blog)

Entry first conceived on 27 September 2007, 17:02 UTC, last modified on 15 January 2012, 3:46 UTC
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