[johnzabroski]

Why is Mozilla Firefox written in Rust, then?

The last time I looked at browser benchmarks was in 2016 when Google released benchmarks to brag about its performance over Firefox and Edge. It appears Webkit has released JetStream2 to benchmark JavaScript, WebAssembly and web workers, among other things. But I can't find data showing Mozilla Firefox is ~20% slower than Chrome/Edge today.

[dthul]

Using Firefox to evaluate Rust performance is probably not a good idea since only parts of it are written in Rust today.

But it's the first time I hear someone say that Rust is supposedly fundamentally slower than C++. I don't believe this to be a statement that can be substantiated, seeing that some of the fastest programs out there (ripgrep and hyper to name just two) are written in Rust.

[The_rationalist]

Facts: On average rust is 10% slower on the banchmarkgame: https://benchmarksgame-team.pages.debian.net/benchmarksgame/...

But they use llvm instead of gcc for c++, and gcc is in average 20% faster than clang. Therefore, rust is 30% slower, at least on heavily optimised programs.

And hyper is not the fastest http server, but the actix one is one of the fastest yes.

[steveklabnik]

> Facts: On average rust is 10% slower on the banchmarkgame

That does not show it's 10% slower on average; it shows that C++ is 0.9917938291x as fast as Rust. They both have some where they win by 30%, most are closer, Rust is just faster on average.

> But they use llvm instead of gcc for c++,

C++ g++ g++ (Ubuntu 9.2.1-9ubuntu2) 9.2.1 20191008

?

> gcc is in average 20% faster than clang.

Extremely citation needed.

[igouy]

> faster on average

What kind-of time measurements? What kind-of average?

This chart shows some time measurements:

https://benchmarksgame-team.pages.debian.net/benchmarksgame/...

:and the geometric mean is faster for the C++ programs, but the median seems faster for the rust programs.

Statistical artifacts?

[steveklabnik]

> What kind-of time measurements? What kind-of average?

I interpreted the parent to mean a simple average, so I did exactly that: calculated the percentage for each, and averaged them. In the colloquial term, "mean".

[igouy]

typo ? "the colloquial term" is "average", the specific term is "mean".

[The_rationalist]

Geometric mean is the implicit default measurement for benchmarking

[igouy]

> On average rust is 10% slower on the banchmarkgame

If that claim was true …

> gcc is in average 20% faster than clang

and if that claim was true …

then we might guess the rust programs average could be 10% faster than the C++ programs average, if both used the same compiler backend

— because those rust programs were compiled with llvm but those c++ programs were compiled with gcc.

[pdimitar]

IMO the jury is still out. I am pretty sure that C++ veterans that can cleverly utilise any and all performance tricks (minus resorting to an assembly language) and can thus beat any other language.

But I -- like yourself -- am much more interested in the applicability of a language in everyday tools, plus in getting the most performance with the least amount of dark magic involved.

BTW, `ripgrep` definitely made me work better and faster.

[The_rationalist]

Firefox is far more than 20% slower than Chrome today but is not strictly a direct cause of using rust. https://www.phoronix.com/scan.php?page=article&item=firefox-...