perf(pm): TTY-gate progress + cooperative yield in spawn loop

crates/pm/src/service/install.rs

@@ -21,7 +21,8 @@ use crate::util::downloader::download_stats;
 use crate::util::json::load_package_lock_json_from_path;
 use crate::util::linker::link;
 use crate::util::logger::{
-    PROGRESS_BAR, finish_progress_bar, log_progress, print_install_counts, start_progress_bar,
+    finish_progress_bar, log_progress, print_install_counts, progress_inc, progress_set_length,
+    start_progress_bar,
 };
 use utoo_ruborist::compat::{is_cpu_compatible, is_os_compatible};
 
@@ -87,9 +88,24 @@ pub async fn install_packages(
 
         if let Some(packages) = groups.get(depth) {
             for (path, package) in packages.iter() {
+                // Cooperative scheduling hint: tells the runtime "I did
+                // a tick of work" and yields when the per-task budget
+                // (default 128) exhausts. Before #2903's TTY-gate the
+                // implicit yield came from indicatif's mutex acquire on
+                // every progress_inc call; on non-TTY (CI, piped output)
+                // that's now a no-op and the synchronous loop body runs
+                // ~2000 packages back-to-back without giving the runtime
+                // a window to drain socket reads on in-flight tarball
+                // downloads. Pcap measured `tcp.analysis.zero_window`
+                // events climb 0 → 14-16 without this hint; with it,
+                // back to 0. Cost is ~5ns when budget isn't exhausted
+                // (the common case — JoinHandle.await downstream resets
+                // budget naturally).
+                tokio::task::consume_budget().await;
+
                 // Skip packages based on omit config
                 if should_omit_package(package, omit) {
-                    PROGRESS_BAR.inc(1);
+                    progress_inc(1);
                     continue;
                 }
                 let path = path.clone();
@@ -108,28 +124,28 @@ pub async fn install_packages(
                     if package.link.is_some() {
                         let link_name = extract_package_name(&path);
                         if link_name.is_empty() {
-                            PROGRESS_BAR.inc(1);
+                            progress_inc(1);
                             continue;
                         }
                         link(Path::new(&resolved), Path::new(&path))
                             .await
                             .with_context(|| format!("Link failed: {resolved} -> {path}"))?;
-                        PROGRESS_BAR.inc(1);
+                        progress_inc(1);
                         continue;
                     }
 
                     // skip when cpu or os is not compatible
                     if let Some(ref cpu) = package.cpu
                         && !is_cpu_compatible(cpu)
                     {
-                        PROGRESS_BAR.inc(1);
+                        progress_inc(1);
                         continue;
                     }
 
                     if let Some(ref os) = package.os
                         && !is_os_compatible(os)
                     {
-                        PROGRESS_BAR.inc(1);
+                        progress_inc(1);
                         continue;
                     }
 
@@ -153,18 +169,18 @@ pub async fn install_packages(
                                 tracing::warn!(
                                     "Optional dependency {name} failed (ignored): {e:#}"
                                 );
-                                PROGRESS_BAR.inc(1);
+                                progress_inc(1);
                                 return Ok(());
                             }
                             return Err(e);
                         }
-                        PROGRESS_BAR.inc(1);
+                        progress_inc(1);
                         log_progress(&format!("{name} resolved"));
                         update_package_binary(&target_path, &name).await
                     });
                     clone_tasks.push(task);
                 } else {
-                    PROGRESS_BAR.inc(1);
+                    progress_inc(1);
                 }
             }
         }
@@ -260,7 +276,7 @@ impl InstallService {
 
         if !package_lock.packages.is_empty() {
             start_progress_bar();
-            PROGRESS_BAR.set_length(package_lock.packages.len() as u64);
+            progress_set_length(package_lock.packages.len() as u64);
         }
 
         let link_start = Instant::now();

crates/pm/src/util/logger.rs

@@ -161,6 +161,27 @@ pub fn log_progress(text: &str) {
     PROGRESS_BAR.set_message(text.to_string());
 }
 
+/// TTY-gated `PROGRESS_BAR.inc(1)`. Non-TTY callers pay no Mutex cost —
+/// indicatif's `inc` always takes the internal `Mutex<ProgressState>`
+/// write-lock even with a hidden draw target, which contends across the
+/// install loop's spawned tasks.
+#[inline]
+pub fn progress_inc(n: u64) {
+    if !*IS_TTY {
+        return;
+    }
+    PROGRESS_BAR.inc(n);
+}
+
+/// TTY-gated `PROGRESS_BAR.set_length`. Same rationale as [`progress_inc`].
+#[inline]
+pub fn progress_set_length(len: u64) {
+    if !*IS_TTY {
+        return;
+    }
+    PROGRESS_BAR.set_length(len);
+}
+
 // Global timer for log_time/log_time_end
 static START_TIME: OnceCell<Instant> = OnceCell::new();