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Comment by phkahler | Hacker News Reader

Right. The whole time I was thinking the hardware change probably exacerbated an existing software issue. Then I saw this:

"The issue has been fixed with .NET Core 2.1 and .NET Framework 4.8 Preview contains also the fixes for it."

And by the end of the article I was thinking their code might just run faster as a single thread on a ~4GHz processor.

Another thought was why do they have so much resource contention in the first place? That seems fishy.

Another thought: Perhaps they should write it in Rust with all of its "fearless concurrency" claims. While I'm skeptical of those claims, The exercise would probably highlight some of the real issues.

Any way I look at it, I keep thinking it's a software design problem.

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Rust doesn't magically fix resources contention. It just provides safe concurrency primitives (and the surrounding language semantics) that make it difficult -to-impossible to misuse in such a way as to cause a deadlock or race condition.

Right, so if the language forces you to eliminate deadlocks and race conditions you may find less need for spinlocks which are the problem here.

Speculation on my part. I'm not actually advocating Rust but I am thinking about a project to give it a try.

if the language forces you to eliminate deadlocks and race conditions

It does not, it only prevents a specific problem known as a data race, which is an issue related to memory/ownership.

There is no deadlock protection. And race conditions are a much broader set of issues than just data races.

I like rust, just want to keep your expectations in check.

If I remember correctly, rust doesn't help with deadlocks - you still have to be careful of them. Though it does have primitives to help significantly with race conditions

The primitives help with taking the same lock around every access to a location. They don't help in finding locations that should use the same lock; you can easily write Rust code that uses too many separate locks and as such can still have race conditions.

> difficult -to-impossible to misuse in such a way as to cause a deadlock or race condition

Rust doesn't solve deadlocks or race conditions. Rust only makes it hard to accidentally share a memory location, but that's only a very small part of the problem, race conditions being a fundamental part of computer science, being baked into any language that supports expressing and joining asynchronous processes.

I would be generous in agreeing with a statement about Rust making it a little more difficult to end up with a deadlock or unwanted race condition, except that's not true when compared with many other high level languages.

Also nothing is impossible until you prove it via formal methods (e.g. TLA+).

> Rust only makes it hard to accidentally share a memory location,

Not just a memory location, any value. You can use the tools Rust gives you on any piece of state you care to manage - a database connection, a remote server, the office coffee machine - represent it as a value and Rust will let you check that it's owned where you want it to be owned, borrowed where you want it to be borrowed and so on.

> Also nothing is impossible until you prove it via formal methods (e.g. TLA+).

What's the distinction you're drawing between something like TLA+ and something like the Rust borrow checker?

> I would be generous in agreeing with a statement about Rust making it a little more difficult to end up with a deadlock or unwanted race condition, except that's not true when compared with many other high level languages.

It is easy to specifically describe what Rust prevents: unsynchronized memory access from multiple threads. What other high-level languages allow read-write shared-memory multithreading and guarantee that?

> Also nothing is impossible until you prove it via formal methods (e.g. TLA+).

The fact that unsynchronized memory access is impossible in safe Rust (modulo compiler bugs, CPU bugs, etc.) is something that nobody seriously doubts. It's obvious. I'm glad people are working on proving it, but the proof is an academic exercise.

> It is easy to specifically describe what Rust prevents: unsynchronized memory access from multiple threads. What other high-level languages allow read-write shared-memory multithreading and guarantee that?

Pony maybe? https://www.ponylang.org/discover/#what-is-pony

At least that's my impression of its reference capabilities.

No, it's something that Pony relatively explicitly doesn't allow: AIUI, iso (non-aliasable, read/write), val (aliasable, read-only, no write) and tag (aliasable, no read or write) are the only things that can be shared between actors/threads.

You're right about deadlocks and general race conditions. I was confused. Rust only (statically) prevents data races (arguably the only form of race condition that is always undesirable). Rust does nothing to prevent deadlocks.

The advantage of Rust over, e.g. Java, then, is that Rust can prevent data races at compile time?

Yup.

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