From 7d466570f47f67819edb556ccd3658b9073ec088 Mon Sep 17 00:00:00 2001
From: Junliang HU <jlhu@cse.cuhk.edu.hk>
Date: Fri, 9 Dec 2022 21:11:46 +0800
Subject: [PATCH 1/2] Add numThreads in config to avoid spawning lots of
 threads every time

---
 crates/rust-analyzer/src/config.rs       | 7 +++++++
 crates/rust-analyzer/src/global_state.rs | 2 +-
 crates/rust-analyzer/src/task_pool.rs    | 3 ++-
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 6c0d712a4f..a90775933c 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -403,6 +403,9 @@ config_data! {
         /// Whether to show `can't find Cargo.toml` error message.
         notifications_cargoTomlNotFound: bool      = "true",
 
+        /// How many worker threads in the main loop. The default `null` means to pick automatically.
+        numThreads: Option<usize> = "null",
+
         /// Expand attribute macros. Requires `#rust-analyzer.procMacro.enable#` to be set.
         procMacro_attributes_enable: bool = "true",
         /// Enable support for procedural macros, implies `#rust-analyzer.cargo.buildScripts.enable#`.
@@ -1454,6 +1457,10 @@ impl Config {
         }
     }
 
+    pub fn main_loop_num_threads(&self) -> usize {
+        self.data.numThreads.unwrap_or(num_cpus::get_physical().try_into().unwrap_or(1))
+    }
+
     pub fn typing_autoclose_angle(&self) -> bool {
         self.data.typing_autoClosingAngleBrackets_enable
     }
diff --git a/crates/rust-analyzer/src/global_state.rs b/crates/rust-analyzer/src/global_state.rs
index 4e8bc8d646..fb9415b5dc 100644
--- a/crates/rust-analyzer/src/global_state.rs
+++ b/crates/rust-analyzer/src/global_state.rs
@@ -134,7 +134,7 @@ impl GlobalState {
 
         let task_pool = {
             let (sender, receiver) = unbounded();
-            let handle = TaskPool::new(sender);
+            let handle = TaskPool::new_with_threads(sender, config.main_loop_num_threads());
             Handle { handle, receiver }
         };
 
diff --git a/crates/rust-analyzer/src/task_pool.rs b/crates/rust-analyzer/src/task_pool.rs
index aeeb3b7c58..616e449984 100644
--- a/crates/rust-analyzer/src/task_pool.rs
+++ b/crates/rust-analyzer/src/task_pool.rs
@@ -8,12 +8,13 @@ pub(crate) struct TaskPool<T> {
 }
 
 impl<T> TaskPool<T> {
-    pub(crate) fn new(sender: Sender<T>) -> TaskPool<T> {
+    pub(crate) fn new_with_threads(sender: Sender<T>, threads: usize) -> TaskPool<T> {
         const STACK_SIZE: usize = 8 * 1024 * 1024;
 
         let inner = threadpool::Builder::new()
             .thread_name("Worker".into())
             .thread_stack_size(STACK_SIZE)
+            .num_threads(threads)
             .build();
         TaskPool { sender, inner }
     }

From 9f5a547b3f91bee46e3015eb11cce8772820398b Mon Sep 17 00:00:00 2001
From: Junliang HU <jlhu@cse.cuhk.edu.hk>
Date: Fri, 9 Dec 2022 21:36:35 +0800
Subject: [PATCH 2/2] Regenerate config

---
 docs/user/generated_config.adoc | 5 +++++
 editors/code/package.json       | 9 +++++++++
 2 files changed, 14 insertions(+)

diff --git a/docs/user/generated_config.adoc b/docs/user/generated_config.adoc
index db41c7bf10..f59a524364 100644
--- a/docs/user/generated_config.adoc
+++ b/docs/user/generated_config.adoc
@@ -604,6 +604,11 @@ Number of syntax trees rust-analyzer keeps in memory. Defaults to 128.
 --
 Whether to show `can't find Cargo.toml` error message.
 --
+[[rust-analyzer.numThreads]]rust-analyzer.numThreads (default: `null`)::
++
+--
+How many worker threads in the main loop. The default `null` means to pick automatically.
+--
 [[rust-analyzer.procMacro.attributes.enable]]rust-analyzer.procMacro.attributes.enable (default: `true`)::
 +
 --
diff --git a/editors/code/package.json b/editors/code/package.json
index ad5f97bb19..26a1e81f13 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -1137,6 +1137,15 @@
                     "default": true,
                     "type": "boolean"
                 },
+                "rust-analyzer.numThreads": {
+                    "markdownDescription": "How many worker threads in the main loop. The default `null` means to pick automatically.",
+                    "default": null,
+                    "type": [
+                        "null",
+                        "integer"
+                    ],
+                    "minimum": 0
+                },
                 "rust-analyzer.procMacro.attributes.enable": {
                     "markdownDescription": "Expand attribute macros. Requires `#rust-analyzer.procMacro.enable#` to be set.",
                     "default": true,