Memory leak & poor performance when using Rust Language Server on Linux

[alexheretic]

I've traced a atom memory & performance issue when using RLS (Rust Language Server) to this project.

When watching a rust project directory with nsfw and running RLS, nsfw will leak memory and consume cpu.

Downstream: rust-lang/atom-ide-rust#104

Steps to reproduce

• Install node & rustup latest stable (see https://rustup.rs)
• Install rls rustup component add rls
• Checkout a rust project that isn't tiny, say regex d4b9419

git clone https://github.com/rust-lang/regex
cd regex
git checkout d4b9419

• Construct a minimal node project with nsfw in another directory

{
  "name": "ntmp",
  "version": "1.0.0",
  "dependencies": {
    "@atom/nsfw": "1.0.23"
  }
}

• Watch the rust project

node                                                                                                                              
> require('@atom/nsfw')('/home/alex/project/regex', events => {}).then(w => w.start())

• Run RLS in the rust project

cd regex
rls --cli

• Restart RLS & re-run to see further leakage.

With these steps it's easy enough to see nsfw consume several GB of ram & lots of CPU as RLS is running. This memory usage/leakage is worse on larger rust projects.

RLS uses cargo/rustc to compile code and generates lots of data in the ./target directory in the project which is what triggers this issue. Strangely though running cargo directly doesn't cause this memory issue. I not sure why this is RLS specific.