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ros2_timer_latency_measurement package from ros2_timer_latency_measurement repo

ros2_timer_latency_measurement

ROS Distro
github

Package Summary

Tags	No category tags.
Version	0.0.0
License	TODO: License declaration
Build type	AMENT_CMAKE
Use	RECOMMENDED

Repository Summary

Description
Checkout URI	https://github.com/hsgwa/ros2_timer_latency_measurement.git
VCS Type	git
VCS Version	master
Last Updated	2020-10-27
Dev Status	UNKNOWN
Released	UNRELEASED
Tags	No category tags.
Contributing	Help Wanted (-) Good First Issues (-) Pull Requests to Review (-)

Package Description

measurement tool for nanosleep latency and timer callback latency.

Additional Links

No additional links.

Maintainers

hasegawa

Authors

No additional authors.

README.md

ros2_timer_latency_measurement

Overview

This measure the accuracy of the timer when the priority of the ROS2-generated child thread change. Following Latencies are measured.

Latency of nanosleep wake-up between child threads policies TS and RR There are two patterns of child threads, as follows
- child threads : rclcpp::init() generated only.
- child threads : rclcpp::init() + node decleration generated
Latency of Timer callback between nanosleep + spin_some vs spin Each measurement point is as follows.
- nanosleep + spin_some : The latency between the time nanosleep expected to wake-up and the callback is actually called.
- spin : The latency between the time callback expected to be called and actually called.

Setup

Environment

The main environment is as follows:

Hardware : Raspberry Pi 3B +
OS : ubuntu 18.04 4.19.55-rt24-v7+
ROS Distro : ROS 2 Eloquent Elusor
DDS : FastRTPS(v1.9.3P1) or CycloneDDS(0.1.0)

For building environment, see setup.md.

Cyclictest results before and after setup.

Build

source ~/ros2_eloquent/install/setup.bash
cd ~/ros2_ws/src
git clone https://github.com/hsgwa/ros2_timer_latency_measurement.git
colcon build --symlink-install

Run

Example

source ~/ros2_eloquent/install/setup.bash
source ~/ros2_ws/install/local_setup.sh
export RMW_IMPLEMENTATION=rmw_fastrtps_cpp

taskset -c 1 ~/ros2_ws/build/ros2_timer_latency_measurement/init_thread \
        --use_realtime_child_thread \
        --timeseries_filename timeseries.csv \
        --hist_filename raw/hist.csv \
        --topn_filename raw/topn.csv \
        --rttest_args -m 200mb -d 200mb -t 98 -s rr -u 10ms -i 720000

Excuetable files

The following is a list of executable files.

executable file	measurement target	conditons
init_thread	nanosleep wake-up latency	rclcpp::init generated thread
init_and_node_thread_thread	nanosleep wake-up latency	rclcpp::init and DDS generated threads
timer_cb_latency_spin_some	callback latency	nanosleep + spin_some executor
timer_cb_latency_spin	callback latency	single thread executor

Comand line options

Each executable can be configured with command line options.

options	descriptions
–use_realtime_child_thread	Set child threads policy. real-time (inherit rttest_args)
–unuse_realtime_child_thread	Set child threads policy. TS
–timeseries_filename	Set filepath to export time-series cav data
–hist_filename	Set filepath to export histgram csv data
–topn_filename	Set filepath to export topN latency data.

The options after –rttest_args will be sent to rttest. The availabile options are as follows. Here, rttest version is tag:0.9.0.

options	descriptions
-m	Set maximum stack prefault size for static stack prefaulting.
-d	Set maximum heap prefault size for dynamic memory prefaulting.
-t	Set the thread priority of all threads launched by the test program.
-s	Set scheduling policy fifo/rr
-u	Specify the update period.
-i	Specify how many iterations to run the real-time loop.

Please see rttest for more information on each option.

Results

Comparison of nanosleep wake-up latency between child threads policies TS and RR

File truncated at 100 lines see the full file

CHANGELOG

No CHANGELOG found.

Package Dependencies

Deps	Name
	ament_cmake
	rclcpp
	rttest
	tlsf_cpp
	rcl
	ament_lint_auto
	ament_lint_common

System Dependencies

No direct system dependencies.

Dependant Packages

No known dependants.

Launch files

No launch files found

Messages

No message files found.

Services

No service files found

Plugins

No plugins found.

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