Help on tuning the Linux kernel for soft real-time requiremen ts

Zajac Adam-AAZ004 Adam.Zajac at
Tue Oct 19 08:44:52 EST 2004


It sounds like you're doing exactly what we've been trying to achieve.
We're trying to meet soft real-time deadlines that are in order of seconds
The only differences between our systems are:
- kernel 2.4.20
- HZ = 100
- Compact Flash

We tried to do a similar thing to the scenario you described where we were
running all other threads with SCHED_OTHER, and the thread with real-time
priority with RoundRobin scheduler policy. We keep experiencing the greatest
slips for such file system intensive operations like gzip and tar.
Also, for an experiment, we tried to turn disk caching off, which helped
meeting the deadlines a little but slowed down all file transfers
To eliminate the question on the compact flash performance we tried using
NFS. Using NFS  yielded similar results (missed deadlines) to performing the
transfers with the cflash card.

Did you have to set anything special at your kernel config file (.config)?
Did you need to apply low-latency patch separately or the MV kernel you have
came pre-patched?

Adam Zajac

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