Improving `codegen_crate` and `link` Steps Compilation Performance in Rust

[vincent-herlemont]

I've been experiencing performance issues with my Rust compilation times and I'm looking for some advice on how to optimize it. Here's my current situation:

• The most time-consuming steps in my compilation process are codegen_crate (~5s) and link (~10s).
• The total compilation time is ~20 seconds.
• I've used the -Z self-profile option to gather this information.

[profile.dev]
incremental = true

[lib]
path = "src/lib.rs"
crate-type = ["lib", "staticlib", "cdylib"]

[dependencies]
flutter_rust_bridge = { version = "=1.67.0", features = ["uuid"] }
indexmap = "1.7"
thiserror = "1.0"
anyhow = "1.0"
walkdir = "2.3.2"
sled = "0.34.7"
parking_lot = { version = "=0.11.2", features = ["deadlock_detection"] } # Use to detect deadlocks for sled.
serde_json = "1.0"
serde = { version = "1.0", features = ["derive"] }
bincode = { version = "2.0.0-rc.2", features = ["serde"] }
chrono = { version = "0.4", features = ["serde"] }
once_cell = "1.17"
strum_macros = "0.24"
sentry = { version = "0.30", features = ["anyhow"] }
tracing = "0.1"
tracing-subscriber = { version = "0.3", features = ["env-filter"] }
sentry-tracing = "0.30"
sentry-backtrace = "0.30"
openssl = { version = "0.10", features = ["vendored"] }
enum_dispatch = "0.3"
crossbeam = "0.8"
heck = "0.4"
itertools = "0.10"
notify = "5.1"
notify-debouncer-mini = "0.2"
blake3 = "1.3"
camino = "1.1"

# Tools
regex = "1.7"

# Analyse
rake = "0.3.3"
lingua = { version = "1.4.0", default-features = false, features = ["english", "french", "italian", "spanish", "dutch"] }
infer = "0.13"
stop-words = "0.7.0"

## Search
milli = { git = "https://github.com/meilisearch/meilisearch.git", rev="9882029", default-features = false }
either = "1.8"

[dependencies.uuid]
version = "1.3"
features = [
    "v4",                # Lets you generate random UUIDs
    "fast-rng",          # Use a faster (but still sufficiently random) RNG
    "macro-diagnostics", # Enable better diagnostics for compile-time UUIDs
]

[dev-dependencies]
assert_fs = "1.0"
serial_test = "1.0"
include_dir = "0.7"
filetime = "0.2"

[features]
test = []

What are the improvements, in order of the best ways to improve build performance, for now I'm guessing to do:

• Split the project into a sub-crate.
• Change the linker used. Try mold

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Related interesting topics about compilation performance:

• Tips for Faster Rust Compile Times | Matthias Endler
• Why is my Rust build so slow?

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I'd appreciate any suggestions on how to improve the performance of these steps, or any other general advice for speeding up the compilation process. Thanks in advance for your help!

[kpreid]

There might be some useful advice here:

Fast Rust Builds

A lot of the article is about CI more than interactive builds, but some is relevant. In particular, if you can reduce the amount of monomorphization, that will reduce the total code size that the codegen and link steps have to process.