prioritize event handing over indexing

If we index gazillion libraries simultaneously, we fill the threadpool
and so the main loop fails to turn, although there isn't really any
significant blocking inside the loop itself.

1 files changed, 15 insertions, 4 deletions

diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index 7fc0b8f50..c43637351 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -47,6 +47,8 @@ enum Task {
     Notify(RawNotification),
 }
 
+const THREADPOOL_SIZE: usize = 8;
+
 pub fn main_loop(
     internal_mode: bool,
     ws_root: PathBuf,
@@ -54,7 +56,7 @@ pub fn main_loop(
     msg_receiver: &Receiver<RawMessage>,
     msg_sender: &Sender<RawMessage>,
 ) -> Result<()> {
-    let pool = ThreadPool::new(8);
+    let pool = ThreadPool::new(THREADPOOL_SIZE);
     let (task_sender, task_receiver) = unbounded::<Task>();
     let (ws_worker, ws_watcher) = workspace_loader();
 
@@ -164,6 +166,11 @@ fn main_loop_inner(
     pending_requests: &mut FxHashSet<u64>,
     subs: &mut Subscriptions,
 ) -> Result<()> {
+    // We try not to index more than THREADPOOL_SIZE - 3 libraries at the same
+    // time to always have a thread ready to react to input.
+    let mut in_flight_libraries = 0;
+    let mut pending_libraries = Vec::new();
+
     let (libdata_sender, libdata_receiver) = unbounded();
     loop {
         log::trace!("selecting");
@@ -191,6 +198,7 @@ fn main_loop_inner(
             Event::Lib(lib) => {
                 feedback(internal_mode, "library loaded", msg_sender);
                 state.add_lib(lib);
+                in_flight_libraries -= 1;
             }
             Event::Msg(msg) => match msg {
                 RawMessage::Request(req) => {
@@ -219,8 +227,10 @@ fn main_loop_inner(
             },
         };
 
-        for lib in state.process_changes() {
-            let (root, files) = lib;
+        pending_libraries.extend(state.process_changes());
+        while in_flight_libraries < THREADPOOL_SIZE - 3 && !pending_libraries.is_empty() {
+            let (root, files) = pending_libraries.pop().unwrap();
+            in_flight_libraries += 1;
             let sender = libdata_sender.clone();
             pool.execute(move || {
                 let start = ::std::time::Instant::now();
@@ -230,7 +240,8 @@ fn main_loop_inner(
                 sender.send(data).unwrap();
             });
         }
-        if state.roots_to_scan == 0 {
+
+        if state.roots_to_scan == 0 && pending_libraries.is_empty() && in_flight_libraries == 0 {
             feedback(internal_mode, "workspace loaded", msg_sender);
         }