3 files changed, 34 insertions, 18 deletions

diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index 7822be2e2..15bf519c9 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -29,9 +29,6 @@ use crate::{
     Result, ServerConfig,
 };
 
-const THREADPOOL_SIZE: usize = 8;
-const MAX_IN_FLIGHT_LIBS: usize = THREADPOOL_SIZE - 3;
-
 #[derive(Debug)]
 pub struct LspError {
     pub code: i32,
@@ -60,6 +57,25 @@ pub fn main_loop(
 ) -> Result<()> {
     log::info!("server_config: {:#?}", config);
 
+    // Windows scheduler implements priority boosts: if thread waits for an
+    // event (like a condvar), and event fires, priority of the thread is
+    // temporary bumped. This optimization backfires in our case: each time the
+    // `main_loop` schedules a task to run on a threadpool, the worker threads
+    // gets a higher priority, and (on a machine with fewer cores) displaces the
+    // main loop! We work-around this by marking the main loop as a
+    // higher-priority thread.
+    //
+    // https://docs.microsoft.com/en-us/windows/win32/procthread/scheduling-priorities
+    // https://docs.microsoft.com/en-us/windows/win32/procthread/priority-boosts
+    // https://github.com/rust-analyzer/rust-analyzer/issues/2835
+    #[cfg(windows)]
+    unsafe {
+        use winapi::um::processthreadsapi::*;
+        let thread = GetCurrentThread();
+        let thread_priority_above_normal = 1;
+        SetThreadPriority(thread, thread_priority_above_normal);
+    }
+
     let mut loop_state = LoopState::default();
     let mut world_state = {
         let feature_flags = {
@@ -168,7 +184,7 @@ pub fn main_loop(
         )
     };
 
-    let pool = ThreadPool::new(THREADPOOL_SIZE);
+    let pool = ThreadPool::default();
     let (task_sender, task_receiver) = unbounded::<Task>();
     let (libdata_sender, libdata_receiver) = unbounded::<LibraryData>();
 
@@ -210,7 +226,7 @@ pub fn main_loop(
             )?;
         }
     }
-
+    world_state.analysis_host.request_cancellation();
     log::info!("waiting for tasks to finish...");
     task_receiver.into_iter().for_each(|task| {
         on_task(task, &connection.sender, &mut loop_state.pending_requests, &mut world_state)
@@ -371,7 +387,8 @@ fn loop_turn(
         loop_state.pending_libraries.extend(changes);
     }
 
-    while loop_state.in_flight_libraries < MAX_IN_FLIGHT_LIBS
+    let max_in_flight_libs = pool.max_count().saturating_sub(2).max(1);
+    while loop_state.in_flight_libraries < max_in_flight_libs
         && !loop_state.pending_libraries.is_empty()
     {
         let (root, files) = loop_state.pending_libraries.pop().unwrap();
@@ -586,12 +603,14 @@ fn on_notification(
 
 fn on_check_task(
     task: CheckTask,
-    world_state: &WorldState,
+    world_state: &mut WorldState,
     task_sender: &Sender<Task>,
 ) -> Result<()> {
     match task {
         CheckTask::ClearDiagnostics => {
-            let cleared_files = world_state.check_watcher.state.write().clear();
+            let state = Arc::get_mut(&mut world_state.check_watcher.state)
+                .expect("couldn't get check watcher state as mutable");
+            let cleared_files = state.clear();
 
             // Send updated diagnostics for each cleared file
             for url in cleared_files {
@@ -600,11 +619,9 @@ fn on_check_task(
         }
 
         CheckTask::AddDiagnostic(url, diagnostic) => {
-            world_state
-                .check_watcher
-                .state
-                .write()
-                .add_diagnostic_with_fixes(url.clone(), diagnostic);
+            let state = Arc::get_mut(&mut world_state.check_watcher.state)
+                .expect("couldn't get check watcher state as mutable");
+            state.add_diagnostic_with_fixes(url.clone(), diagnostic);
 
             // We manually send a diagnostic update when the watcher asks
             // us to, to avoid the issue of having to change the file to
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 8e43f0575..666f2ee29 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -674,8 +674,7 @@ pub fn handle_code_action(
         res.push(action.into());
     }
 
-    for fix in world.check_watcher.read().fixes_for(&params.text_document.uri).into_iter().flatten()
-    {
+    for fix in world.check_watcher.fixes_for(&params.text_document.uri).into_iter().flatten() {
         let fix_range = fix.location.range.conv_with(&line_index);
         if fix_range.intersection(&range).is_none() {
             continue;
@@ -895,7 +894,7 @@ pub fn publish_diagnostics(
             tags: None,
         })
         .collect();
-    if let Some(check_diags) = world.check_watcher.read().diagnostics_for(&uri) {
+    if let Some(check_diags) = world.check_watcher.diagnostics_for(&uri) {
         diagnostics.extend(check_diags.iter().cloned());
     }
     Ok(req::PublishDiagnosticsParams { uri, diagnostics, version: None })
diff --git a/crates/ra_lsp_server/src/world.rs b/crates/ra_lsp_server/src/world.rs
index e7a0acfc7..3059ef9ec 100644
--- a/crates/ra_lsp_server/src/world.rs
+++ b/crates/ra_lsp_server/src/world.rs
@@ -63,7 +63,7 @@ pub struct WorldSnapshot {
     pub workspaces: Arc<Vec<ProjectWorkspace>>,
     pub analysis: Analysis,
     pub latest_requests: Arc<RwLock<LatestRequests>>,
-    pub check_watcher: Arc<RwLock<CheckState>>,
+    pub check_watcher: CheckState,
     vfs: Arc<RwLock<Vfs>>,
 }
 
@@ -220,7 +220,7 @@ impl WorldState {
             analysis: self.analysis_host.analysis(),
             vfs: Arc::clone(&self.vfs),
             latest_requests: Arc::clone(&self.latest_requests),
-            check_watcher: self.check_watcher.state.clone(),
+            check_watcher: (*self.check_watcher.state).clone(),
         }
     }