Why am I experience slow launch times with cargo?

[douglaslassance]

It takes about 30 seconds versus 3 with a simple cargo run.

Configuration

• Windows 11 Pro 10.0.26200 Build 26200
• Visual Studio Code 1.105.1
• CodeLLDB 1.11.7

rustup show

installed toolchains
--------------------
stable-x86_64-pc-windows-msvc (active, default)
1.77.2-x86_64-pc-windows-msvc
1.85.0-x86_64-pc-windows-msvc

active toolchain
----------------
name: stable-x86_64-pc-windows-msvc
active because: it's the default toolchain
installed targets:
  x86_64-pc-windows-msvc

rustc --version

rustc 1.90.0 (1159e78c4 2025-09-14)

Terminal

warning: unused manifest key: target.x86_64-pc-windows-msvc.linker
Finished `dev` profile [optimized + debuginfo] target(s) in 0.40s

2025-10-18T08:56:35.134850Z  INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "Windows 11 Pro", kernel: "26200", cpu: "AMD Ryzen 9 7940HS w/ Radeon 780M Graphics", core_count: "8", memory: "31.2 GiB" }
2025-10-18T08:56:37.181583Z  INFO bevy_render::renderer: AdapterInfo { name: "NVIDIA GeForce RTX 4070 Laptop GPU", vendor: 4318, device: 10272, device_type: DiscreteGpu, driver: "NVIDIA", driver_info: "581.42", backend: Vulkan }
2025-10-18T08:56:38.772590Z  INFO bevy_render::batching::gpu_preprocessing: GPU preprocessing is fully supported on this device.
2025-10-18T08:56:38.784080Z  INFO bevy_winit::system: Creating new window project (0v0)

Debug console

Console is in 'commands' mode, prefix expressions with '?'.
Loading Rust formatters from C:\Users\user\.rustup\toolchains\stable-x86_64-pc-windows-msvc\lib/rustlib/etc
Launching: c:\Users\user\Projects\project\target\debug\project.exe
Launched process 17496 from 'c:\Users\user\Projects\project\target\debug\project.exe'

Launch JSON

{
    "version": "0.2.0",
    "configurations": [
        {
            "type": "lldb",
            "request": "launch",
            "name": "Run project",
            "cargo": {
                "args": ["build"],
            },
        }
    ]
}

[vadimcn]

LLDB's PDB debug info reader is pretty slow, so for large projects it may take a while.
Can you use x86_64-pc-windows-gnu toolchain? (see https://github.com/vadimcn/codelldb/wiki/Windows)

Otherwise, I wonder if "initCommands": ["settings set symbols.load-on-demand true"] would help?
Another thing you can try is "lldb.useNativePDBReader": true (this one goes into settings.json), though it'll probably mess up visualization of std types.

[douglaslassance]

For context, this is my Cargo.toml.

[package]
name = "project"
version = "0.1.0"
edition = "2024"

[dependencies]
bevy = "0.17.2"
log = { version = "*", features = [
    "max_level_debug",
    "release_max_level_warn",
] }

[features]
default = []
fast_compile = ["bevy/dynamic_linking"]

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

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

I am not sure how to set up the x86_64-pc-windows-gnu toolchain but will read and figure it out.

Adding "initCommands": ["settings set symbols.load-on-demand true"] to launch.json exits with code 3221225477.

Verbose logging: off  (Use "lldb.verboseLogging" setting to change)
Platform: win32 x64
Initial debug configuration: {
  type: 'lldb',
  request: 'launch',
  name: 'Run project',
  cargo: { args: [ 'build' ] },
  initCommands: [ 'settings set symbols.load-on-demand true' ],
  __configurationTarget: 6
}
Running: cargo build --message-format=json --color=always --config=target.'cfg(all())'.runner='c:\Users\user\.vscode\extensions\vadimcn.vscode-lldb-1.11.7\bin\codelldb-launch'
Cargo exited with code 0 
Raw artifacts:
{
  fileName: 'c:\\Users\\user\\Projects\\project\\target\\debug\\project.exe',
  name: 'project',
  kind: 'bin'
}
Filtered artifacts: 
{
  fileName: 'c:\\Users\\user\\Projects\\project\\target\\debug\\project.exe',
  name: 'project',
  kind: 'bin'
}
Resolved debug configuration: {
  type: 'lldb',
  request: 'launch',
  name: 'Run project',
  initCommands: [ 'settings set symbols.load-on-demand true' ],
  __configurationTarget: 6,
  relativePathBase: 'c:\\Users\\user\\Projects\\project',
  _adapterSettings: {
    displayFormat: 'auto',
    showDisassembly: 'auto',
    dereferencePointers: true,
    suppressMissingSourceFiles: true,
    evaluationTimeout: 5,
    consoleMode: 'commands',
    sourceLanguages: null,
    scriptConfig: {},
    evaluateForHovers: true,
    commandCompletions: true
  },
  program: 'c:\\Users\\user\\Projects\\project\\target\\debug\\project.exe',
  sourceLanguages: [ 'rust' ]
}
Launching adapter
liblldb: c:\Users\user\.vscode\extensions\vadimcn.vscode-lldb-1.11.7\lldb\bin\liblldb.dll
environment: {}
settings: {
  evaluateForHovers: true,
  commandCompletions: true,
  sourceLanguages: [ 'rust' ]
}
Debug adapter exit code=3221225477, signal=null.

Adding "lldb.useNativePDBReader": true to settings.json seems to make no difference.

[douglaslassance]

Might be also useful to add that I tried running the project on macOS, and I'm getting about 20 seconds launch times.