Messages in this thread | | | Date | Mon, 02 Jul 2007 15:18:12 +0200 | From | John Sigler <> | Subject | [CONFIG_PREEMPT_RT] High frequency periodic timer |
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Hello everyone,
I have been experimenting with the CONFIG_PREEMPT_RT patch for a few months. Specifically kernel 2.6.20.7-rt8.
http://rt.wiki.kernel.org/index.php/Main_Page
I've been running into some unexpected problems, so I wanted to ask those who have some experience with this patch what they thought.
Here's a brief description of my application:
System A periodically sends timestamped packets. These packets travel over a network, or through a network emulator, and get randomly dropped or delayed by a random amount of time. These packets reach system B at some point. System B uses the timestamp to re-send the packets smoothly, as if they had been produced on B, with only a constant time-shift. Basically, B acts as a "dejittering" router.
I have implemented this with high-resolution timers. Every time the timer fires, I send one packet. In "parallel", I buffer incoming packets that arrive from system A.
Consider 1316-byte packets and a 80 Mbit/s stream bit rate.
This means the timer period is 1316*8 / 80 = 131.6 µs
I've been wondering whether having such a small period (high frequency) might be a problem / challenge for the real-time kernel (scheduler, IRQ handler, other component).
The CPU used is mid-range (i.e. 1.5 GHz Celeron M) single core, and it easily copes with just the receiving part.
But I have seen some odd behavior (random crashes in my program) that must mean I have made some incorrect assumptions.
What do you all think?
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