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Comment by mumblemumble | Hacker News Reader

One important difference in all of those is that they are decisions made by the user of the programming language, not the author.

Sub-optimal performance decisions made by the user are their own business (and, perhaps, their customers'), and not really the language authors' concern. The converse is not true. Sub-optimal performance decisions made by the language authors end up affecting everybody.

I agree that saying a 1% difference would disqualify it as a systems language is hyperbolic. I disagree with the assertion that it's not a big deal. Having a core development team that considers 1% to be a big deal is a very desirable trait in a systems language. Achieving very high performance goals often comes through an accretion of many such 1% (and sub-1%) decisions.

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The difference in performance between existing systems languages is greater than 1%. This is just not a big deal. People will not choose their systems language based on a 1% performance difference. It's so far down the list of considerations that it's a total non-issue.

Would Linus accept a language for core Linux work that came with a 1% penalty?

He just did, it's called Rust. And if someone invented a language 5% faster than C. He'd still use C. If someone had invented a language faster than C when he started working on Linux, he would still have chosen C. He didn't pick it because it was the fastest (and it likely wasn't back then - C compilers have come a long way.)

The whole point of Rust is to not require runtime checks by pushing safety to the type system; why would it be slower than C?

Because practice is not the same as theory. It's both faster and slower than C, depending on the program, but overall slower. The answer to why is deeply complex and varies on a case-by-case basis. Rust is far more complex than C, so some language features compile down to a LOT more IR (intermediate representation) than C, and LLVM is left to try and make the best of it. Many problems in compilers are NP-complete, and the compiler will use heuristics and other techniques to get an approximately good enough answer. Like register allocation. The more complex the starting state, the less well that tends to work out. But there's other things too, Rust has bounds checks for example, while C often does not. C has null-terminated strings, while Rust strings store a length. Rust doesn't have aliasing, but doesn't yet (last I checked anyway) optimize for that. It will one day though. This is just touching on an extremely nuanced and complex subject. But C is typically faster than Rust, and will likely stay that way.

This question is impossible to answer in a vacuum. What if the language made developers 90% more productive or 90% less likely to introduce a memory bug or offered 3x faster compiler times? A 1% runtime performance hit would be well worth it if that were the case. Perhaps with the extra time available, developers could find better algorithms/ways of expressing their programs that would ultimately lead to faster runtime performance on average even with the 1% hit in certain microbenchmarks.

He certainly hasn't accepted D as a language for core Linux work, despite the benefits without any supposed performance tradeoffs. And he uses GCC for compilation, despite the existence of specialized compilers that offer better runtime performance.

Would Linus accept a C compiler that replaced malloc/free with a GC? It's only 1%.

No, but not because of performance. Malloc/free is required for deterministic runtime behavior. A GC would take that away.

Would Linus accept a language that is more than 1% slower than optimal? Yes, he already does. It's called C. C is slower than optimal assembly.

He chose C because it is easier to write large systems in a higher level language, and it is far easier to write cross platform code in.

That is a common mistake, malloc()/free() aren't deterministic, specially in threaded code, heaviliy loaded system, ISO C doesn't even provide guarantees of how deterministic they should come back to the caller across C implementations.

Sure but you control when you call them.

If you call them explicitly, you control the call.

There is no control over the duration, or what third party code is doing with them.

In D you also control when to call the GC.

I think the larger issue for Linux would be lack of determinism and memory bloat due to the presence of a collector.

I agree that it is not the 1% that matters but rather the 10% hit that comes from multiple failures to see a 1% hit as material.

I would argue that 10% still doesn't matter as much as other things. But it's starting to matter.

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