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This benchmarks serves as a case study on RT.js, a practical real-time scheduler for web applications. It shows, that the standard JavaScript run-to-completion semantics hit their limits, when there are compute intensive operations. Also its First-Come-First-Served (FCFS) scheduling policy does not allow prioritizing jobs over other ones, for example making jobs, which respond to user input, more important than ones, which do background computation.

RT.js solves that, by introducing Preemption Points ahead-of-time into existing JavaScript code, and scheduling the jobs with its own scheduler. Therefore no modification of the JavaScript engine is necessary.

Links

• RT.js Project Website
• RT.js on GitHub
• Published Paper on RT.js

Task Types

This benchmark consists of four tasks:

Box Task

Invoked every frame, moves the box, Deadline: 10ms

Input Task

Invoked on every ENTER stroke, creates an AES-task, sporadic, Deadline: 100ms

AES Task

Encrypts the input 250 times and decrypts it again; posts the results in the console, sporadic, Deadline: 500ms

SchedCAT Task Set

A generated set of tasks (n=15); the jobs buisy wait for their WCET; combined utilization: 0.75; Period in [1,52]s, Deadline = Period, WCET in [15,1815]ms

Options

Step Length

Denotes the amount of seconds each subtest runs, i.e. how long only the box animation is active, then the box+input, box+schedcat, box+schedcat+input; rt.js+box,...

Run Benchmark

Run automatic tests, switching every permutation of the options on; running with JavaScript semantics (every job will run-to-completion, without any preemption, in a strict first-come-first-served manner. Data will be automatically input for the input-task to process.

Enable RT.js Scheduler

Switch between the JavaScript scheduling scheme (run-to-completion, with a first-come-first served policy) and our RT.js scheduler (pseudo-preemption between jobs with an earliest deadline first polcy).

Enable SchedCAT load

Introduce the generated task set into the system

Encrypt Input

Enable the Input and AES Tasks; every input (entered with ENTER), will be encrypted and descrypted 250 times, and the result will be posted to the console.

Animate Box

Enables or disables the box-animation, i.e. stops the box from moving