sched-sim

sched-sim

A browser simulator for LLM serving schedulers with an animated Gantt chart that compares continuous batching, chunked prefill, shortest-job-first and disaggregated serving. For engineers and students.

Made by prajwalpujari16 on Hugging Face. These notes are Mindket's, written from its Space page and README; the app's own files and license are on Hugging Face.

About

What it is: sched-sim is a browser simulator for how LLM serving schedulers order work. Behind the page is an event-by-event simulation of three ideas: batching that never pauses, prefill split into pieces, and a long prefill that holds up the requests queued behind it. The result plays as an animated Gantt chart. It is a static page, so nothing runs on a server.

Who it suits: It suits people who want to see why scheduling choices change how long requests wait.

Title: Who might use this simulator
Industry | Who uses it | How they use it | Example
ML infrastructure | Serving engineers | Compare scheduling policies before changing a system | Play the blocking case and the chunked case one after the other
Education | Students | Learn how a serving scheduler works | Watch the Gantt player step through requests
AI research | Researchers | Reason about latency effects of scheduling | Try the shortest-job-first policy

If you need to tune a live serving stack with real traffic, you can skip it, since this is a simulation.

Where to use it: You can use it online or open its files on your own computer.

• Web browser: the Space's page on Hugging Face, with nothing to install
• Windows, macOS or Linux: the downloaded files, opened in a browser
• Python: a PyPI package of the same name, named in the readme

Title: What the simulator is good for
Use case | Who | What they get back
See prefill blocking | Students | An animation of one long prompt holding up shorter ones
Compare policies | Engineers | Gantt views for chunked prefill, shortest-job-first and disaggregated serving
Teach scheduling | Instructors | A visual to walk a class through

How to set it up: The hosted page needs nothing. To get the files you need Python and pip.

• Python, with pip
• Any web browser

1. Install the huggingface_hub package.
2. Download the Space's files into a folder.
3. Move into that folder.
4. Open index.html in a web browser.

pip install -U huggingface_hub
hf download prajwalpujari16/sched-sim --repo-type space --local-dir sched-sim
cd sched-sim

The readme also names a PyPI package, which installs with this command.

pip install sched-sim

How to use it: Open the Space online, or open index.html from your downloaded folder. Then press play on the Gantt player and compare the policies it demonstrates.

Title: What the Gantt player demonstrates
Tool | What it does
Head-of-Line prefill blocking | Shows how a long prefill delays the requests behind it
Chunked prefill | Splits prefill into chunks of 512 tokens, the Sarathi approach
Shortest-job-first | Orders requests so the shortest run first
Disaggregated serving | Separates the stages of serving across resources

Example: You play the Head-of-Line blocking scene and watch short requests queue behind a long prefill. Then you play the chunked prefill scene and compare how the same requests line up on the Gantt chart.

For newcomers and experts: If you are new to this, start with the blocking scene. Prefill is the step where the model reads the prompt, and a long one can hold up everything behind it.

If you know the field, the page runs a discrete-event simulation and compares Head-of-Line blocking against Sarathi-style chunked prefill with a 512-token chunk, shortest-job-first and disaggregated serving. It names a serving traces dataset.

Open the simulator
Pick a scheduling policy
The simulation runs the requests
The Gantt player animates the result

Good to know: This is a simulation of scheduling, not a live serving engine.

• Static page: plain HTML and CSS, with no server code
• Dataset: the Space names a serving traces dataset
• License: apache-2
• Cost to run: none named
• Data it reaches: nothing beyond its own files is named in the notes
• Not for: tuning a live serving system with real traffic

On Hugging Face, 13 November 2026

• Likes: 1
• Built with: static
• License: apache-2.0

Links

• Space: https://huggingface.co/spaces/prajwalpujari16/sched-sim
• Files: https://huggingface.co/spaces/prajwalpujari16/sched-sim/tree/main

Try it

Open the Space in your browser, or copy it to your own Hugging Face account from its page. Nothing in this kit runs by itself.