mrchrisadams
commented
1 year ago I vaguely remember some of this now, and profiler docs are helpful too.
The output that Firefox Profiler needs is generated by the Gecko Profiler, a piece of c++ code inside Firefox.
If you have the ability to run javascript in the context of driving the browser, there's a profiler object you can interact with.
Here's the code from the corresponding docs profile page:
(() => {
// I think these are the settings telling the profile what to profile, how often to sample, and
// setting a limit of how many samples to create.
const settings = {
entries: 1000000,
interval: 0.4,
features: ["js", "stackwalk", "threads", "leaf"],
threads: ["GeckoMain", "Compositor"]
};
// start the profiler. and recording stuff
Services.profiler.StartProfiler(
settings.entries,
settings.interval,
settings.features,
settings.features.length,
settings.threads,
settings.threads.length
);
// dump the output somewhere, currently to the console I guess?
setTimeout(() => {
Services.profiler.getProfileDataAsync().then(profile => {
for (let i = 0; i < profile.threads.length; i++) {
const thread = profile.threads[i];
}
console.log(profile);
// Stopping the profiler will delete the data in the buffer.
Services.profiler.StopProfiler();
});
}, 500);
})();I can't remember if sitespeed lets you run javascript in this context easily, or how best to write this to a file, but presumably, if you know how to do these two things, then it's not a significant leap to be able to consume them in the Profiler, or even expose some metrics for presentation inside sitespeed.
soulgalore
mgifford
canova
Your question
Hi folks.
I think I asked this in slack aaaaages ago, but I realise it's probably better to ask in a public forum instead.
Is it technically possible to run sitespeed using Firefox, and as part of a test run, generate an output file for the scripted actions taken, that can be consumed by the firefox profiler tool listed below, maaaaaybe a bit a bit like how you can use Sitespeed to create Harfiles for later analysis??
If so, in high level terms how would you do it?
I'm asking in the context of wanting to automate test runs using the Firefox Profiler, but it's beyond my knowledge of both Sitespeed and of Firefox Profiler.
This talk about the power profiling tool for Firefox is quite a good intro https://fosdem.org/2023/schedule/event/energy_power_profiling_firefox/
As is the deck: https://fosdem.org/2023/schedule/event/energy_power_profiling_firefox/attachments/slides/5537/export/events/attachments/energy_power_profiling_firefox/slides/5537/FOSDEM_2023_Power_profiling_with_the_Firefox_Profiler.pdf