rustc-perf VS mold

> 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

I think this is unlikely to gain traction. I say that no to discourage you, just to explain.

- The community has an instinctive distrust of closed source or a compiler from an untrusted source. If you’re familiar with the Trusting Trust attack you’ll understand why.

- Dev tools in every language ecosystem are almost always free, unless they involve some kind of hosting. People aren’t used to opening their wallets. Look the experience of the guy who built the mold linker(https://github.com/rui314/mold). Far superior to the state of art, improves incremental compiles a lot, widely applicable across ecosystems (C, C++, Rust), CPU architectures and Operating Systems. You don’t even have to modify your compiler, just need to point to his linker. He’s even giving it away for free for personal use. But still, almost no one uses it. The inertia of the established options is really high.

- It’s not complex enough. Think about the complexity involved in the cranelift backend. No one can seriously recreate the efforts of bjorn3. If we could have, we would have. But the idea idea here can be recreated, especially by the experts who already built incremental compilation into rustc.

- But if your solution is truly complex, like the parallel frontend, the burden of maintaining a fork would be too high. You’d have to spend all your time rebasing.

Again I’m not trying to discourage you, just stating the difficulties of making a business in the dev tools space. You would be better off contributing this excellent work to the community and trying a different tack.

I initially thought this would be about the mold linker (https://github.com/rui314/mold)

I assume this submission is trying to highlight the specific message (2023-01-24) : https://github.com/rui314/mold/issues/190#issuecomment-14028...

Fyi... the author wrote a more expansive blog post about selling dev tools a few months later (2023-06-06) and there was a related HN thread about it: https://news.ycombinator.com/item?id=36225016

Loongson's LoongArch CPU has been supported. (03b1a1c)

I'm amazed at how quickly the author responds to requests: https://github.com/rui314/mold/issues/1057

From the report to the fix in less than two days.

I'm not sure how competitive it will be with lld, especially if we consider ThinLTO (which takes multiple minutes on 64-core machine) - it can make the advantages of mold insignificant.

What other solutions have you tried for the problem of slow linking? You haven't even said which linker and what flags you're using. I haven't actually tried it, but the author of gold has an even faster linker called mold: https://github.com/rui314/mold

> Mold did it first, though: https://github.com/rui314/mold

Before LLD?