OPFS concurrency tester using multiple independent Workers. Disclaimer: concurrency in OPFS is currently a pain point and timing/concurrency mitigation in this environment is highly unpredictable!

URL flags: pass a number of workers using the workers=N URL flag. Set the time between each workload with interval=N (milliseconds). Set the number of worker iterations with iterations=N. Enable OPFS VFS verbosity with verbose=1-3 (output goes to the dev console). Enable/disable "unlock ASAP" mode (higher concurrency, lower speed) with unlock-asap=0-1.

Achtung: if it does not start to do anything within a couple of seconds, check the dev console: Chrome often fails with "cannot allocate WasmMemory" at startup. Closing and re-opening the tab usually resolves it.