profiler VS rustc-perf

Probably your best bet is to use the Firefox Profiler once it starts hogging the CPU to try to see what it's doing. I'd be happy to take a look at the result although I don't have a lot of experience at diagnosing performance problems; hopefully the profile will make it obvious what's going on.

I tried using the https://profiler.firefox.com/ and running with:

You can try to reproduce while taking a profile using the Firefox profiler, then share it in the #perf:mozilla.org room on Mozilla's Matrix instance.

Run a profiling session for ~30 sec when you notice something is running slower than you expect, see https://profiler.firefox.com/. Share results here if you want help interpreting them.

Next time, send a SIGABRT to the main process (kill -6 $(pidof firefox)) and use the resulting backtrace (you will find a link to the crash report in about:crashes) to file a bug. A performance profile could be useful, but you'll need to know first what to capture. This seems like a graphics issue, so try the Graphics preset. Share a link to your report.

https://profiler.firefox.com will be useful if you can capture and share it to developers.

If you can reproduce it in safe mode and a clean profile, capture a performance profile using the clean profile while trying to load a problematic webpage, don't remove any information from it, and share it here (although it's typically not easy for users to analyse them), or file a bug with it attached.

Next time, capture a performance profile using the Graphics preset, and kill the browser by entering kill -6 $(pidof firefox) in a shell. This will create a bug report (unless debian disables the crash reporter) that would indicate where Firefox is stuck at. You might need to use an official build to get useful results.

> what do people use to run benchmarks on CI?

Typically, you purchase/rent a server that does nothing but sequentially run queued benchmarks (and the size/performance of this server doesn't really matter, as long as the performance is consistent), then sends the report somewhere for hosting and processing. Of course, this could be triggered by something running in CI, and the CI job could wait for the results, if benchmarking is an important part of your workflow.

But CI and benchmarks really shouldn't be run on the same host.

> What does the rust project use?

It's not clear exactly where the Rust benchmark "perf-runner" is hosted, but here are the specifications of the machine at least: https://github.com/rust-lang/rustc-perf/blob/414230abc695bd7...

> What do other projects use?

Essentially what I described above, a dedicated machine that runs benchmarks. The Rust project seems to do it via GitHub comments (as I understand https://github.com/rust-lang/rustc-perf/tree/master/collecto...), others have API servers that respond to HTTP requests done from CI/chat, others have remote GUIs that triggers the runs. I don't think there is a single solution that everyone/most are using.

A lot of effort is spent to reduce the size of structs in the Rust compiler

https://nnethercote.github.io/2023/03/24/how-to-speed-up-the...

3% and 6% of improvement doesn't seem like much, but at the level of rustc those big wins

Performance of Rustc must be continously tracked (here https://perf.rust-lang.org/) because if you don't proactively fight against bloat, the tendency is that the code will become slower over time (due to new features etc)

hmm really really hard to answer :'), it's tradeoffs I think, no matter what you think Rust (cmiiw, I'm not qualified to say this) has (and probably in the future will adds more with guards on compiler metrics https://perf.rust-lang.org/) several phases that given the diffs to other language, might not available to any language compiler out there, if it's available I think rustc already did their best in here (some already being parallized etc etc, might be wrong since I can't refs any reference MRs, but it does exists though labels regarding this)

About a year ago I was looking for a tool like Rust perf for my application code. I did some research and found a lot of prior art. However, nothing checked all the boxes I was looking for, so I built Bencher!

https://www.pingcap.com/blog/rust-compilation-model-calamity... is a good overview. In general it varies depending on the crate but we track the performance at https://perf.rust-lang.org/ - if you look at cargo, for example, over 60% of the time is spent in codegen through LLVM: https://perf.rust-lang.org/detailed-query.html?commit=222d1f...

Something like https://perf.rust-lang.org/?

The performance full-report link is dead: https://github.com/rust-lang/rustc-perf/blob/master/triage/2022-10-04.md