Use install concurrency for bytecode compilation too (#11615)

Instead of always using all available threads for bytecode compilation,
respect `UV_CONCURRENT_INSTALLS`, so the parallelism is configurable
instead of hardcoded. We reuse the install limit since bytecode
compilation only runs after install.

Cargo.lock

@@ -4928,6 +4928,7 @@ dependencies = [
  "uv-cache",
  "uv-cli",
  "uv-client",
+ "uv-configuration",
  "uv-distribution-filename",
  "uv-distribution-types",
  "uv-extract",

crates/uv-dev/Cargo.toml

@@ -19,6 +19,7 @@ workspace = true
 uv-cache = { workspace = true, features = ["clap"] }
 uv-cli = { workspace = true }
 uv-client = { workspace = true }
+uv-configuration = { workspace = true }
 uv-distribution-filename = { workspace = true }
 uv-distribution-types = { workspace = true }
 uv-extract = { workspace = true, optional = true }

crates/uv-dev/src/compile.rs

@@ -4,6 +4,7 @@ use clap::Parser;
 use tracing::info;
 
 use uv_cache::{Cache, CacheArgs};
+use uv_configuration::Concurrency;
 use uv_python::{EnvironmentPreference, PythonEnvironment, PythonRequest};
 
 #[derive(Parser)]
@@ -33,6 +34,7 @@ pub(crate) async fn compile(args: CompileArgs) -> anyhow::Result<()> {
     let files = uv_installer::compile_tree(
         &fs_err::canonicalize(args.root)?,
         &interpreter,
+        &Concurrency::default(),
         cache.root(),
     )
     .await?;

crates/uv-installer/src/compile.rs

@@ -1,4 +1,3 @@
-use std::num::NonZeroUsize;
 use std::panic::AssertUnwindSafe;
 use std::path::{Path, PathBuf};
 use std::process::Stdio;
@@ -14,6 +13,7 @@ use tokio::sync::oneshot;
 use tracing::{debug, instrument};
 use walkdir::WalkDir;
 
+use uv_configuration::Concurrency;
 use uv_fs::Simplified;
 use uv_static::EnvVars;
 use uv_warnings::warn_user;
@@ -71,6 +71,7 @@ pub enum CompileError {
 pub async fn compile_tree(
     dir: &Path,
     python_executable: &Path,
+    concurrency: &Concurrency,
     cache: &Path,
 ) -> Result<usize, CompileError> {
     debug_assert!(
@@ -78,13 +79,10 @@ pub async fn compile_tree(
         "compileall doesn't work with relative paths: `{}`",
         dir.display()
     );
-    let worker_count = std::thread::available_parallelism().unwrap_or_else(|err| {
-        warn_user!("Couldn't determine number of cores, compiling with a single thread: {err}");
-        NonZeroUsize::MIN
-    });
+    let worker_count = concurrency.installs;
 
     // A larger buffer is significantly faster than just 1 or the worker count.
-    let (sender, receiver) = async_channel::bounded::<PathBuf>(worker_count.get() * 10);
+    let (sender, receiver) = async_channel::bounded::<PathBuf>(worker_count * 10);
 
     // Running Python with an actual file will produce better error messages.
     let tempdir = tempdir_in(cache).map_err(CompileError::TempFile)?;
@@ -92,7 +90,7 @@ pub async fn compile_tree(
 
     debug!("Starting {} bytecode compilation workers", worker_count);
     let mut worker_handles = Vec::new();
-    for _ in 0..worker_count.get() {
+    for _ in 0..worker_count {
         let (tx, rx) = oneshot::channel();
 
         let worker = worker(

crates/uv/src/commands/mod.rs

@@ -47,6 +47,7 @@ pub(crate) use tool::uninstall::uninstall as tool_uninstall;
 pub(crate) use tool::update_shell::update_shell as tool_update_shell;
 pub(crate) use tool::upgrade::upgrade as tool_upgrade;
 use uv_cache::Cache;
+use uv_configuration::Concurrency;
 use uv_distribution_types::InstalledMetadata;
 use uv_fs::{Simplified, CWD};
 use uv_installer::compile_tree;
@@ -147,6 +148,7 @@ pub(super) struct DryRunEvent<T: Display> {
 /// See the `--compile` option on `pip sync` and `pip install`.
 pub(super) async fn compile_bytecode(
     venv: &PythonEnvironment,
+    concurrency: &Concurrency,
     cache: &Cache,
     printer: Printer,
 ) -> anyhow::Result<()> {
@@ -154,7 +156,12 @@ pub(super) async fn compile_bytecode(
     let mut files = 0;
     for site_packages in venv.site_packages() {
         let site_packages = CWD.join(site_packages);
-        files += compile_tree(&site_packages, venv.python_executable(), cache.root())
+        files += compile_tree(
+            &site_packages,
+            venv.python_executable(),
+            concurrency,
+            cache.root(),
+        )
         .await
         .with_context(|| {
             format!(

crates/uv/src/commands/pip/operations.rs

@@ -554,7 +554,7 @@ pub(crate) async fn install(
     }
 
     if compile {
-        compile_bytecode(venv, cache, printer).await?;
+        compile_bytecode(venv, &concurrency, cache, printer).await?;
     }
 
     // Construct a summary of the changes made to the environment.