GSOC_RTA

2020 Google Summer of Code (Non-Preemptive / Limited preemptive in Response Time Analysis)

Readthedocs

[Table of Contents]

1. Milestone with the goal of each phase

2. Intention & contribution to the open source community

3. Contents

4. Instruction

1. Milestone with the goal of each phase

• Response Time Analysis for non-preemptive environment (Phase 1)
• Response Time Analysis for limited-preemptive environment (Phase 2)
• Blocking analysis for non-preemptive and limited-preemptive environment (Phase 3)

2. Intention & contribution to the open source community

There are several paper about response time analysis but not many open source code that developer can use as reference or implementation can be found in the internet. This project is my contribution to the open source community in this matter. In this project, you can find method to calculate response time in different preemptive environment: non-preemptive, cooperative, or a mixed of the above.

3. Contents and how to use

My utlimate target is to implement response time analysis in a mixed environemnt, where task can be surrounded by different tasks with different preemptive type, from preemptive, cooperative to non-preemptive.

My implementation are located in NPandPRta class. Which include several response time analysis methods. Refer to each methods' javadoc for more info, I will only mention here the most important/useful function go to my readthedoc if you want a full documentation

<NPandPRta.java>

There is something need to be mentioned before you try, this class is created based on WATERS2019 model, the functions are tested using that model. But you should be able to ultilize this class without many problem as long as you provided 3 input parameters:

• Amalthea model - The model that you will use to ultilize this method, this should be given when you create the class object
• Integer array (ia) - This is a representation of how task is allocated to cores, the location of each element represent task, and the value represent core. I.e. {0,2,3,1,1,2} : first task is assigned to first core of the model, 2nd task is assigned to 3rd core, 3rd task is assigned to 4th core and so on
• Task - the task you want to calculate its response time

Also additionally there are 3 other parameters:

• executionCase : TimeType.WCET - just put this like this, since you would want to calculate worst case response time most of the time, change to BCET if you want something different.
• pTypeArray: a customized array that you can use to define tasks' preemption type. Leave null if don't use. Check javadoc for more info.
• usePtypeArray: boolean variable to announce whether you want to use pTypeArray or not. Leave false if don't use.

Below are the important functions that you will probably use most of the time. For the list of all function, refer to the javadoc, readthedoc or open the class, I left lots of comment their

getRTAinMixedPreemptiveEnvironment Calculate response time of task in mixed environment. Drop the task, the integer mapping array, and the model (again this class is made mainly for WATERS2019 derived model, but it should work on other as well) and you get your response time. I also opt in an option where you can input your own preemptive type array. Where you can change task‘s preemptive type without changing it in the model. setSchedubilityCheck This function set a boolean variable where you can enable/disable schedubility check. Which means if you set to false. Every RTA functions will return the value without checking whether that response time bigger than task’s period or not. getResponseTimeViaLevelI Calculate resposne time of task in preemptive environment via level-i busy window technique. Pretty vanilla/basic implementation. getResponseTimeViaRecurrenceRelation Calculate resposne time of task in preemptive environment via recurrence relation. Again very basic execution of how response time is calculated Should give the same result as response time level-i. getPureExecutionTime Using the well-known semantics, where task is run as follow: READ -> EXECUTION -> WRITE Calculate all of the element from each step, sum all of them and we have task's execution time.

<Blocking.java>

Blocking analysis, calculate blocking time of semaphore(critical section) when they are exist, or else calculate time other tasks have to wait due to global resource occupancy (task had to wait because other task is reading/writing label) ) Same as the NPandPRta.java, this class also created based on WATER 2019 model.

Again I only listed important/useful function. For more info, please refer functions' javadoc and readthedoc

getGlobalBlockingTime Calculate task's global blocking time ( time blocked by task from other cores) due to semaphore lock. If there is no semaphore, the function will calculate blocking time due to resource being read/write by other task. The blocking policy is Priority Ceiling Protocol FYI getLocalBlockingTime Same with getGlobalBlockingTime, but this time we calculate blocking time due to local task (task within same core)

4. Instruction

First of all, you will need to pull the big repo.

https://git.eclipse.org/c/app4mc/org.eclipse.app4mc.tools.git/

Check out the app4mc0.9.8/gsoc20npRTA. This is the branch that have my implementation

1. Under responseTime-analyzer > plugins > src >...> gsoc_rta folder You will find NPandPRta class. This is the implementation source file. One can calculate task's response time in different environment using this.

2. Under responseTime-analyzer > plugins > src >...> gsoc_rta >‘test’ folder, there is NPandPNumerical class. This is a numerical example on how functions/equations used in ‘NPandPRta’ work.

3. Under responseTime-analyzer > plugins > src >...> gsoc_rta folder Blocking is also located here, using this will allow you to calculate local and global blocking time of task