Linking taking a very long time?

[catbrained]

Hey, I'm sometimes seeing very long compile times even on simple projects and as far as I can tell it seems to be because of linking.
I'm talking upwards of 10 minutes.

Bevy version 0.16.1
I am using Rust 1.90.0, which uses lld by default.
CPU: AMD Ryzen 7 5800H
I have 16 GB of RAM on this machine, and during the build I consistently had about 2.1 GB of available memory according to btop. (Most of the memory was used by rust-analyzer and Firefox running in the background). I don't have swap enabled.
All data is on an NVME drive.

The build first showed a very large CPU usage, which then quickly dropped down to medium to low usage.

This issue is present even with incremental compilations on seemingly simple changes. For example, in the code below I removed the FpsOverlayPlugin, setup_system, set_overlay_color_system, OverlayColor, and the associated use statements that are no longer needed. The cargo build --timings then took 10m 04s. (See the timings report gist)

Am I doing something wrong?

The `Cargo.toml` for this project

[package]
name = "game-of-life"
version = "0.1.0"
edition = "2024"
license = "AGPL-3.0-only"
authors = ["Linda Siemons <[email protected]>"]

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
bevy = { version = "0.16.1", features = ["bevy_dev_tools", "wayland"] }

[profile.dev]
# Enable a small amount of optimization in the dev profile.
opt-level = 1

[profile.dev.package."*"]
# Enable a large amount of optimization in the dev profile for dependencies.
opt-level = 3

[profile.release]
# Enable more optimization in the release profile at the cost of compile time.
# Compile the entire crate as one unit.
# Slows compile times, marginal improvements.
codegen-units = 1
# Do a second optimization pass over the entire program, including dependencies.
# Slows compile times, marginal improvements.
lto = "thin"

The code for this project

use bevy::{
    dev_tools::fps_overlay::{FpsOverlayConfig, FpsOverlayPlugin},
    diagnostic::{DiagnosticsStore, FrameTimeDiagnosticsPlugin},
    prelude::*,
};

const WINDOW_START_WIDTH: f32 = 800.0;
const WINDOW_START_HEIGHT: f32 = 800.0;

struct OverlayColor;

impl OverlayColor {
    const GREEN: Color = Color::srgb(0.0, 1.0, 0.0);
    const YELLOW: Color = Color::srgb(0.0, 0.5, 0.5);
    const RED: Color = Color::srgb(1.0, 0.0, 0.0);
}

fn main() {
    App::new()
        .add_plugins((
            DefaultPlugins.set(WindowPlugin {
                primary_window: Some(Window {
                    name: Some("bevy app".to_string()),
                    resolution: (WINDOW_START_WIDTH, WINDOW_START_HEIGHT).into(),
                    ..default()
                }),
                ..default()
            }),
            FpsOverlayPlugin {
                config: FpsOverlayConfig {
                    text_config: TextFont {
                        font_size: 42.0,
                        ..default()
                    },
                    text_color: OverlayColor::GREEN,
                    refresh_interval: std::time::Duration::from_millis(100),
                    enabled: true,
                },
            },
        ))
        .add_systems(Startup, setup_system)
        .add_systems(Update, set_overlay_color_system)
        .run();
}

fn setup_system(mut commands: Commands) {
    commands.spawn(Camera2d);
}

fn set_overlay_color_system(
    mut overlay: ResMut<FpsOverlayConfig>,
    diagnostics: Res<DiagnosticsStore>,
) {
    if let Some(fps) = diagnostics.get(&FrameTimeDiagnosticsPlugin::FPS)
        && let Some(value) = fps.value()
    {
        if value < 15.0 {
            overlay.text_color = OverlayColor::RED;
        } else if (15.0..30.0).contains(&value) {
            overlay.text_color = OverlayColor::YELLOW;
        } else {
            overlay.text_color = OverlayColor::GREEN;
        }
    }
}

objdump output

objdump -j .comment -s target/debug/game-of-life

target/debug/game-of-life:     file format elf64-x86-64

Contents of section .comment:
 0000 72757374 63207665 7273696f 6e20312e  rustc version 1.
 0010 39302e30 20283131 35396537 38633420  90.0 (1159e78c4 
 0020 32303235 2d30392d 31342900 4743433a  2025-09-14).GCC:
 0030 2028474e 55292031 342e332e 3000004c   (GNU) 14.3.0..L
 0040 696e6b65 723a204c 4c442032 302e312e  inker: LLD 20.1.
 0050 3820282f 63686563 6b6f7574 2f737263  8 (/checkout/src
 0060 2f6c6c76 6d2d7072 6f6a6563 742f6c6c  /llvm-project/ll
 0070 766d2065 38613266 66636633 32326634  vm e8a2ffcf322f4
 0080 35623864 63653832 63363561 62323761  5b8dce82c65ab27a
 0090 33653234 33306136 62353129 00        3e2430a6b51).

[MushineLament]

https://bevy.org/learn/quick-start/getting-started/setup/#enable-fast-compiles-optional

[catbrained]

I'm aware of that guide. So I guess linking times this long are just to be expected even with lld?
I'm going to enable dynamic linking for development purposes either way, but I'm just trying to figure out if what I'm seeing is normal or due to some mistake on my part.

[MushineLament]

This is my build log,
Windows,
rust version : rustc 1.88.0 (6b00bc388 2025-06-23)

first build:

   Compiling bevy v0.16.1
   Compiling game-of-life v0.1.0 (D:\Mushine\VScode\testbevy)
    Finished `dev` profile [optimized + debuginfo] target(s) in 6m 43s
     Running `target\debug\game-of-life.exe`
2025-09-28T05:14:57.698886Z  INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "Windows 11 Home China", kernel: "26100", cpu: "13th Gen Intel(R) Core(TM) i7-13650HX", core_count: "14", memory: "15.6 GiB" }
2025-09-28T05:14:58.542419Z  INFO bevy_render::renderer: AdapterInfo { name: "NVIDIA GeForce RTX 4050 Laptop GPU", vendor: 4318, device: 10465, device_type: DiscreteGpu, driver: "NVIDIA", driver_info: "566.07", backend: Vulkan }
2025-09-28T05:14:58.872196Z  INFO bevy_render::batching::gpu_preprocessing: GPU preprocessing is fully supported on this device.
2025-09-28T05:14:58.890365Z  INFO bevy_winit::system: Creating new window App (0v1)
2025-09-28T05:15:05.444034Z  INFO bevy_window::system: No windows are open, exiting
2025-09-28T05:15:05.444589Z  INFO bevy_winit::system: Closing window 0v1

second build:

Compiling game-of-life v0.1.0 (D:\Mushine\VScode\testbevy)
  Finished `dev` profile [optimized + debuginfo] target(s) in 15.64s
   Running `target\debug\game-of-life.exe`
2025-09-28T05:18:18.188948Z  INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "Windows 11 Home China", kernel: "26100", cpu: "13th Gen Intel(R) Core(TM) i7-13650HX", core_count: "14", memory: "15.6 GiB" }
2025-09-28T05:18:18.707875Z  INFO bevy_render::renderer: AdapterInfo { name: "NVIDIA GeForce RTX 4050 Laptop GPU", vendor: 4318, device: 10465, device_type: DiscreteGpu, driver: "NVIDIA", driver_info: "566.07", backend: Vulkan }
2025-09-28T05:18:18.963163Z  INFO bevy_render::batching::gpu_preprocessing: GPU preprocessing is fully supported on this device.
2025-09-28T05:18:18.982870Z  INFO bevy_winit::system: Creating new window App (0v1)
2025-09-28T05:18:19.045952Z  INFO game_of_life: start second build

This may seem like a bug