CVSROOT: /cvs/directfb
Module name: linux-fusion
Changes by: dok 20030130 23:24:35
Added files:
tests : .cvsignore latency.c
Log message:
Wrote small test program that stops time of travel of a message.
It creates a new thread for receiving messages (generic receiver code
doing a blocking read and decoding the message headers). The main
thread will send ten messages with a random pause between.
One time stamp is taken just before the message gets sent. The other
time stamp is taken after the receiver decoded the message header.
This piece of code is also the first stand alone example of using the device.
The output (PIII 800, 2.4.20-rc2 preemptive):
Got message with 0.019 ms latency.
Got message with 0.008 ms latency.
Got message with 0.009 ms latency.
Got message with 0.009 ms latency.
Got message with 0.008 ms latency.
Got message with 0.008 ms latency.
Got message with 0.011 ms latency.
Got message with 0.007 ms latency.
Got message with 0.007 ms latency.
Got message with 0.011 ms latency.
These values would be the same if the sender and receiver wouldn't be
two threads but two distinct processes. This also doesn't say anything
sure about the throughput yet, though 1000/0.007 gives a quite sane
value of about 143 thousand messages per second.
I'm not sure if the preemptive kernel patch influences this latency,
but I guess the throughput would be affected.
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