Use appropriate QoS classes throughout the codebase

crates/flycheck/src/lib.rs

@@ -90,7 +90,7 @@ impl FlycheckHandle {
     ) -> FlycheckHandle {
         let actor = FlycheckActor::new(id, sender, config, workspace_root);
         let (sender, receiver) = unbounded::<StateChange>();
-        let thread = stdx::thread::Builder::new(stdx::thread::QoSClass::Default)
+        let thread = stdx::thread::Builder::new(stdx::thread::QoSClass::Utility)
             .name("Flycheck".to_owned())
             .spawn(move || actor.run(receiver))
             .expect("failed to spawn thread");
@@ -409,7 +409,7 @@ impl CargoHandle {
 
         let (sender, receiver) = unbounded();
         let actor = CargoActor::new(sender, stdout, stderr);
-        let thread = stdx::thread::Builder::new(stdx::thread::QoSClass::Default)
+        let thread = stdx::thread::Builder::new(stdx::thread::QoSClass::Utility)
             .name("CargoHandle".to_owned())
             .spawn(move || actor.run())
             .expect("failed to spawn thread");

crates/ide/src/prime_caches.rs

@@ -81,7 +81,7 @@ pub(crate) fn parallel_prime_caches(
             let worker = prime_caches_worker.clone();
             let db = db.snapshot();
 
-            stdx::thread::Builder::new(stdx::thread::QoSClass::Default)
+            stdx::thread::Builder::new(stdx::thread::QoSClass::Utility)
                 .allow_leak(true)
                 .spawn(move || Cancelled::catch(|| worker(db)))
                 .expect("failed to spawn thread");

crates/rust-analyzer/src/bin/main.rs

@@ -85,7 +85,7 @@ fn try_main(flags: flags::RustAnalyzer) -> Result<()> {
             // will make actions like hitting enter in the editor slow.
             // rust-analyzer does not block the editor’s render loop,
             // so we don’t use User Interactive.
-            with_extra_thread("LspServer", stdx::thread::QoSClass::Default, run_server)?;
+            with_extra_thread("LspServer", stdx::thread::QoSClass::UserInitiated, run_server)?;
         }
         flags::RustAnalyzerCmd::Parse(cmd) => cmd.run()?,
         flags::RustAnalyzerCmd::Symbols(cmd) => cmd.run()?,

crates/rust-analyzer/src/dispatch.rs

@@ -88,7 +88,8 @@ impl<'a> RequestDispatcher<'a> {
         self
     }
 
-    /// Dispatches the request onto thread pool
+    /// Dispatches a non-latency-sensitive request onto the thread pool
+    /// without retrying it if it panics.
     pub(crate) fn on_no_retry<R>(
         &mut self,
         f: fn(GlobalStateSnapshot, R::Params) -> Result<R::Result>,
@@ -103,7 +104,7 @@ impl<'a> RequestDispatcher<'a> {
             None => return self,
         };
 
-        self.global_state.task_pool.handle.spawn(QoSClass::Default, {
+        self.global_state.task_pool.handle.spawn(QoSClass::Utility, {
             let world = self.global_state.snapshot();
             move || {
                 let result = panic::catch_unwind(move || {
@@ -124,7 +125,7 @@ impl<'a> RequestDispatcher<'a> {
         self
     }
 
-    /// Dispatches the request onto thread pool
+    /// Dispatches a non-latency-sensitive request onto the thread pool.
     pub(crate) fn on<R>(
         &mut self,
         f: fn(GlobalStateSnapshot, R::Params) -> Result<R::Result>,
@@ -134,7 +135,7 @@ impl<'a> RequestDispatcher<'a> {
         R::Params: DeserializeOwned + panic::UnwindSafe + Send + fmt::Debug,
         R::Result: Serialize,
     {
-        self.on_with_qos::<R>(QoSClass::Default, f)
+        self.on_with_qos::<R>(QoSClass::Utility, f)
     }
 
     /// Dispatches a latency-sensitive request onto the thread pool.
@@ -147,7 +148,7 @@ impl<'a> RequestDispatcher<'a> {
         R::Params: DeserializeOwned + panic::UnwindSafe + Send + fmt::Debug,
         R::Result: Serialize,
     {
-        self.on_with_qos::<R>(QoSClass::Default, f)
+        self.on_with_qos::<R>(QoSClass::UserInitiated, f)
     }
 
     pub(crate) fn finish(&mut self) {

crates/rust-analyzer/src/handlers/notification.rs

@@ -291,7 +291,7 @@ fn run_flycheck(state: &mut GlobalState, vfs_path: VfsPath) -> bool {
             }
             Ok(())
         };
-        state.task_pool.handle.spawn_with_sender(stdx::thread::QoSClass::Default, move |_| {
+        state.task_pool.handle.spawn_with_sender(stdx::thread::QoSClass::Utility, move |_| {
             if let Err(e) = std::panic::catch_unwind(task) {
                 tracing::error!("flycheck task panicked: {e:?}")
             }

crates/rust-analyzer/src/main_loop.rs

@@ -397,7 +397,7 @@ impl GlobalState {
         tracing::debug!(%cause, "will prime caches");
         let num_worker_threads = self.config.prime_caches_num_threads();
 
-        self.task_pool.handle.spawn_with_sender(stdx::thread::QoSClass::Default, {
+        self.task_pool.handle.spawn_with_sender(stdx::thread::QoSClass::Utility, {
             let analysis = self.snapshot().analysis;
             move |sender| {
                 sender.send(Task::PrimeCaches(PrimeCachesProgress::Begin)).unwrap();
@@ -787,7 +787,10 @@ impl GlobalState {
         tracing::trace!("updating notifications for {:?}", subscriptions);
 
         let snapshot = self.snapshot();
-        self.task_pool.handle.spawn(stdx::thread::QoSClass::Default, move || {
+
+        // Diagnostics are triggered by the user typing
+        // so we want computing them to run at the User Initiated QoS.
+        self.task_pool.handle.spawn(stdx::thread::QoSClass::UserInitiated, move || {
             let _p = profile::span("publish_diagnostics");
             let diagnostics = subscriptions
                 .into_iter()

crates/rust-analyzer/src/reload.rs

@@ -185,7 +185,7 @@ impl GlobalState {
     pub(crate) fn fetch_workspaces(&mut self, cause: Cause) {
         tracing::info!(%cause, "will fetch workspaces");
 
-        self.task_pool.handle.spawn_with_sender(stdx::thread::QoSClass::Default, {
+        self.task_pool.handle.spawn_with_sender(stdx::thread::QoSClass::Utility, {
             let linked_projects = self.config.linked_projects();
             let detached_files = self.config.detached_files().to_vec();
             let cargo_config = self.config.cargo();
@@ -260,7 +260,7 @@ impl GlobalState {
         tracing::info!(%cause, "will fetch build data");
         let workspaces = Arc::clone(&self.workspaces);
         let config = self.config.cargo();
-        self.task_pool.handle.spawn_with_sender(stdx::thread::QoSClass::Default, move |sender| {
+        self.task_pool.handle.spawn_with_sender(stdx::thread::QoSClass::Utility, move |sender| {
             sender.send(Task::FetchBuildData(BuildDataProgress::Begin)).unwrap();
 
             let progress = {
@@ -280,7 +280,7 @@ impl GlobalState {
         let dummy_replacements = self.config.dummy_replacements().clone();
         let proc_macro_clients = self.proc_macro_clients.clone();
 
-        self.task_pool.handle.spawn_with_sender(stdx::thread::QoSClass::Default, move |sender| {
+        self.task_pool.handle.spawn_with_sender(stdx::thread::QoSClass::Utility, move |sender| {
             sender.send(Task::LoadProcMacros(ProcMacroProgress::Begin)).unwrap();
 
             let dummy_replacements = &dummy_replacements;

crates/stdx/src/thread.rs

@@ -155,8 +155,6 @@ pub enum QoSClass {
     /// performance, responsiveness and efficiency.
     Utility,
 
-    Default,
-
     /// TLDR: tasks that block using your app
     ///
     /// Contract:
@@ -234,7 +232,6 @@ mod imp {
         let c = match class {
             QoSClass::UserInteractive => libc::qos_class_t::QOS_CLASS_USER_INTERACTIVE,
             QoSClass::UserInitiated => libc::qos_class_t::QOS_CLASS_USER_INITIATED,
-            QoSClass::Default => libc::qos_class_t::QOS_CLASS_DEFAULT,
             QoSClass::Utility => libc::qos_class_t::QOS_CLASS_UTILITY,
             QoSClass::Background => libc::qos_class_t::QOS_CLASS_BACKGROUND,
         };

crates/vfs-notify/src/lib.rs

@@ -34,7 +34,7 @@ impl loader::Handle for NotifyHandle {
     fn spawn(sender: loader::Sender) -> NotifyHandle {
         let actor = NotifyActor::new(sender);
         let (sender, receiver) = unbounded::<Message>();
-        let thread = stdx::thread::Builder::new(stdx::thread::QoSClass::Default)
+        let thread = stdx::thread::Builder::new(stdx::thread::QoSClass::Utility)
             .name("VfsLoader".to_owned())
             .spawn(move || actor.run(receiver))
             .expect("failed to spawn thread");