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2017-04-29 - 05:38
OSADL HOWTOs

HOWTO: Latency Generator (used for calibration purposes)

Quick HOWTO

Download the file archive blocksys-0.4.tgz and type:

tar -zxvf blocksys-0.4.tgz
cd blocksys-0.4
make
modprobe blocksys

Then run the application

./mklatency

or, alternatively, a shell script with the same functionality

./mklatency.sh

Check out the generated latency:

tail /var/log/messages
[..]
[..] kernel: blocksys: CPU #0 will be blocked for 2000000 nops
[..] kernel: blocksys: CPU #0 blocked about 1270 us

You may then wish to check and to calibrate latency analysis tools such as cyclictest or the OSADL Latency Measurement Box by executing mklatency or mklatency.sh while these tools are running. The CYCLES constant in the mklatency.c source file and the $nops shell variable in mklatency.sh define the duration of the latency.