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Comment by s08148692 | Hacker News Reader

I finally gave in to the rust hype and built a new project in it (or my agent fleet did). Almost instant regret. My poor machine with just 2TB HDD and 24 cores was almost immediately crippled by agents each working in their own sandbox, each one building and compiling

Most projects my fleet works on are in other languages (TS, Go, Elixir) and can comfortably handle 10+ agents working in parallel, but not rust. I had to cap the fleet to 5 workers and build a dedicated resource monitor to step in and tidy up every time the disk almost filled up

That and general progress on building is far slower, with far more time spent building and testing than any other language I use.

Ended up rebuilding in Go, the perf gains weren't worth it

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You should have set up https://github.com/mozilla/sccache at minimum. Setting up compiler caching is routine for people coming from older compiled language backgrounds but it's often missed by people coming from languages like JS/TS who have never been exposed to these ideas.

There's a new project called kache https://github.com/kunobi-ninja/kache that takes this even further and handles more edge cases with worktrees, but it's newer.

If you were pulling the entire project fresh and rebuilding everything in every worktree all the time without any caching then it would be frustrating. You could have asked your agent to set up basic caching and solved most of your problem in minutes.

this is the issue with vibing...you don't know what you don't know

Shouldn’t this be part of cargo and enabled by default then ?

Cargo could definitely improve with some inter-project sharing by default, but simultaneously working with a bunch of workspaces of the same project is a very new phenomena...

Up until now, developers only worked on one thing at a time. Maybe two.

Doing 10 separate clean builds to work on 10 things at the same time wasn’t a consideration until very recently.

You really shouldn't build software with rust if your workflow involves 10+ agents. Why aren't you using Python or Typescript for things like that?

Rust is what you use when you want to maximize on the runtime performance. It will build software that requires significantly less memory and maximize the CPU that will save time and energy. It's a system language for writing software meant to access the hardware.

Why would that imply that you wouldn't use a lot of agents?

A couple recs for sccache, which is great, but I upgraded to mbx (https://github.com/jdx/mr-boxington/) which goes beyond sccache by wrapping cargo to give you better rust-specific management, including incremental compilation.

My harness control plane will autoconfigure mbx across all your machines, if you like. https://github.com/BrokkAi/mjolnir/

Most of that time was probably compiling dependencies. If you give it another go, I would recommend a shared sccache.

https://github.com/mozilla/sccache

Even that doesn't fully avoid recompilation of the same crate, due to features changes across the dependency chain.

Changing features should be happening a lot less than building, you surely would go weeks between those after early dev.

first time i've seen rust's compile performance actually act as a filter haha

Make a cargo wrapper (or ask your clanker) with a global build lock.

Cargo run/test/nextest/run only, check/fmt etc should be excluded.

This avoids contention/oversubscription of the CPU which makes builds up to 300% slower from what I measured.

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