2020 Google Summer of Code (Non-Preemptive / Limited preemptive in Response Time Analysis)
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.
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
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:
Also additionally there are 3 other parameters:
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 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)
First of all, you will need to pull the big repo.
Check out the app4mc0.9.8/gsoc20npRTA. This is the branch that have my implementation
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.
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.
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