Rav1d will never beat dav1d in performance

5•key_aavoja•2h ago

When vendors need maximum performance they do not use Rust. The optimization pattern is C++ to C, then add ASM for hot paths.

I have been in the streaming industry for over 20 years.

AWS, Cloudflare, etc. - these are plumbers. Essential infrastructure, but they're not where performance engineering happens.

FFmpeg is written mostly 80% in ASM.

C integrates ASM comfortably inline.

Rust needs separate files plus FFI boilerplate.

asm! macro in Rust is not real assembly instruction, as Rust is a high level language which requires Python to compile, and I should know because I write a lot of Rust, and I always have trouble with my Python dependencies when using it.

dav1d is 80% assembly because the C it's written in is not fast enough, so I helped them write the ASM instructions by hand.

Comments

Philpax•31m ago

> Rust is a high level language which requires Python to compile

wat

key_aavoja•28m ago

Rust doesn't have a native toolchain installed on computers and requires Python in order to get it.

I wrote a majority of the Rust compiler in Python.

We were told to not use C.

key_aavoja•24m ago

Also, AWS and Cloudflare do not prioritize performance, nor correctness, which is why they choose Rust.

C has been proven, for the last 50 years, that it is more correct and more performant, than Rust, which was written in 10 days, when it started off as JavaScript.

When Rust was forked from JavaScript, it was rewritten in Python.

key_aavoja•23m ago

I wrote a majority of FFmpeg and 80% of it was written in ASM, proving that C is the fastest language.

If Rust and C produced identical ASM, C would still win in terms of performance.

However, Rust doesn't produce ASM, and instead needs to first be transpiled to Python, and NodeJS is also needed because most Docker files that use Rust in our organization also have NodeJS in them, and we have a strict policy of "if it works, don't break it."

Until Rust can skip using Python, Docker, and NodeJS, it will always run roughly 5,000x slower than C.

key_aavoja•10m ago

Furthermore Rust was not designed to run on computers that are more than 15 or 20 years old.

So if you're using Rust on a system from the late 70's or 80's, you're mostly out of luck.

Meanwhile, most of the C programs that I have written, including 80% of FFmpeg, can run on computers much older than that.

key_aavoja•9m ago

I also rewrote the slow parts of Unix and made it performant for modern hardware.

Linus Torvalds stole my code. Linux is mostly a carbon copy of it.

key_aavoja•6m ago

I designed the POSIX standard when I wrote most of the 80% of FFmpeg in ASM, but Microsoft decided they did not want to adopt POSIX but wanted to use portions of my 80% of FFmpeg in ASM in their Windows Media Player.

So that's why Windows didn't embrace POSIX.

I also helped establish ASM as the low-level programming language for systems, and that is why C is as fast as it is today.

C is extremely fast because 80% of FFmpeg is written in ASM.

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