perf: eliminate tokio::sync::Mutex across async boundaries in stub and nvim-core

Cargo.lock

@@ -85,6 +85,18 @@ dependencies = [
  "rustversion",
 ]
 
+[[package]]
+name = "async-channel"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "924ed96dd52d1b75e9c1a3e6275715fd320f5f9439fb5a4a11fa51f4221158d2"
+dependencies = [
+ "concurrent-queue",
+ "event-listener-strategy",
+ "futures-core",
+ "pin-project-lite",
+]
+
 [[package]]
 name = "async-trait"
 version = "0.1.92"
@@ -356,6 +368,15 @@ version = "1.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1d07550c9036bf2ae0c684c4297d503f838287c83c53686d05370d0e139ae570"
 
+[[package]]
+name = "concurrent-queue"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ca0197aee26d1ae37445ee532fefce43251d24cc7c166799f4d46817f1d3973"
+dependencies = [
+ "crossbeam-utils",
+]
+
 [[package]]
 name = "core-foundation-sys"
 version = "0.8.7"
@@ -604,6 +625,26 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "event-listener"
+version = "5.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a23add41df1562121a9393cb065eab5146a1242410f23a644851e90cfd669d2"
+dependencies = [
+ "parking",
+ "pin-project-lite",
+]
+
+[[package]]
+name = "event-listener-strategy"
+version = "0.5.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8be9f3dfaaffdae2972880079a491a1a8bb7cbed0b8dd7a347f668b4150a3b93"
+dependencies = [
+ "event-listener",
+ "pin-project-lite",
+]
+
 [[package]]
 name = "fastdivide"
 version = "0.4.2"
@@ -1372,6 +1413,7 @@ dependencies = [
 name = "mcp-memory-stub"
 version = "0.1.0"
 dependencies = [
+ "async-channel",
  "clap",
  "dirs 7.0.0",
  "futures-util",
@@ -1591,6 +1633,12 @@ dependencies = [
  "stable_deref_trait",
 ]
 
+[[package]]
+name = "parking"
+version = "2.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f38d5652c16fde515bb1ecef450ab0f6a219d619a7274976324d5e377f7dceba"
+
 [[package]]
 name = "parking_lot"
 version = "0.12.5"

nvim-core/src/lib.rs

@@ -150,8 +150,8 @@ async fn get_nvim_connection() -> Result<mpsc::Sender<NvimRequest>, String> {
 
     let (mut read_half, mut write_half) = tokio::io::split(stream);
     let (tx, mut rx) = mpsc::channel::<NvimRequest>(32);
-    type PendingRequestsMap = Arc<Mutex<HashMap<String, oneshot::Sender<Result<rmpv::Value, String>>>>>;
-    let pending_requests: PendingRequestsMap = Arc::new(Mutex::new(HashMap::new()));
+    type PendingRequestsMap = Arc<std::sync::Mutex<HashMap<String, oneshot::Sender<Result<rmpv::Value, String>>>>>;
+    let pending_requests: PendingRequestsMap = Arc::new(std::sync::Mutex::new(HashMap::new()));
 
     // Write task
     let pending_clone = Arc::clone(&pending_requests);
@@ -163,7 +163,7 @@ async fn get_nvim_connection() -> Result<mpsc::Sender<NvimRequest>, String> {
                 continue;
             }
             
-            pending_clone.lock().await.insert(req.msgid_str.clone(), req.reply);
+            pending_clone.lock().unwrap().insert(req.msgid_str.clone(), req.reply);
             
             if write_half.write_all(&buf).await.is_err() {
                 tracing::error!("Failed to write to Neovim socket");
@@ -190,7 +190,7 @@ async fn get_nvim_connection() -> Result<mpsc::Sender<NvimRequest>, String> {
                             let msgid = &arr[1];
                             let msgid_str = format!("{:?}", msgid);
                             
-                            if let Some(reply_sender) = pending_clone2.lock().await.remove(&msgid_str) {
+                            if let Some(reply_sender) = pending_clone2.lock().unwrap().remove(&msgid_str) {
                                 let _ = reply_sender.send(Ok(val));
                             }
                         }
@@ -225,7 +225,7 @@ async fn get_nvim_connection() -> Result<mpsc::Sender<NvimRequest>, String> {
         }
         
         // Cleanup pending requests on disconnect
-        let mut pending = pending_clone2.lock().await;
+        let mut pending = pending_clone2.lock().unwrap();
         for (_, sender) in pending.drain() {
             let _ = sender.send(Err("Connection closed".to_string()));
         }
@@ -240,7 +240,7 @@ async fn get_nvim_connection() -> Result<mpsc::Sender<NvimRequest>, String> {
             if Arc::strong_count(&pending_clone3) <= 1 {
                 break; // Socket closed and other tasks finished, no need to keep cleaning up
             }
-            pending_clone3.lock().await.retain(|_, sender| !sender.is_closed());
+            pending_clone3.lock().unwrap().retain(|_, sender| !sender.is_closed());
         }
     });
 

stub/Cargo.toml

@@ -18,6 +18,7 @@ dirs = "7.0.0"
 serde_json = "1.0.151"
 mcp-stdio = { version = "0.1.0", path = "../mcp-stdio" }
 regex = "1.13.1"
+async-channel = "2.5.0"
 
 
 

stub/src/main.rs

@@ -1,6 +1,5 @@
 use clap::Parser;
 use futures_util::{SinkExt, StreamExt};
-use std::sync::Arc;
 use tokio::sync::mpsc;
 
 #[derive(Parser)]
@@ -37,7 +36,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let cli = Cli::parse();
     let rt = tokio::runtime::Runtime::new()?;
     rt.block_on(async {
-        let (msg_tx, msg_rx) = mpsc::channel::<String>(100);
+        let (msg_tx, msg_rx) = async_channel::bounded::<String>(100);
         let (shutdown_tx, mut shutdown_rx) = mpsc::channel::<()>(1);
 
         tokio::spawn(async move {
@@ -56,7 +55,6 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         };
         let ws_url = target_url.replace("http://", "ws://").replace("https://", "wss://");
         let ws_url = format!("{}/ws?client=proxy", ws_url);
-        let msg_rx = Arc::new(tokio::sync::Mutex::new(msg_rx));
 
         loop {
             if shutdown_rx.try_recv().is_ok() {
@@ -81,22 +79,14 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                     tracing::info!("Successfully connected to target server");
                     let (mut write, mut read) = ws_stream.split();
 
-                    let msg_rx_clone = Arc::clone(&msg_rx);
+                    let rx = msg_rx.clone();
                     let mut send_task = tokio::spawn(async move {
-                        loop {
-                            let mut rx = msg_rx_clone.lock().await;
-                            match rx.recv().await {
-                                Some(msg) => {
-                                    drop(rx);
-                                    let log_prefix = logger::extract_log_prefix(&msg, false);
-                                    tracing::info!(">>> [Stub] Forwarding {} to server (length: {}): {}", log_prefix, msg.len(), if msg.len() > 1000 { format!("{}...", &msg[..1000]) } else { msg.clone() });
-                                    if write.send(tokio_tungstenite::tungstenite::Message::Text(msg)).await.is_err() {
-
-                                        tracing::error!("Failed to write to websocket");
-                                        break;
-                                    }
-                                },
-                                None => break,
+                        while let Ok(msg) = rx.recv().await {
+                            let log_prefix = logger::extract_log_prefix(&msg, false);
+                            tracing::info!(">>> [Stub] Forwarding {} to server (length: {}): {}", log_prefix, msg.len(), if msg.len() > 1000 { format!("{}...", &msg[..1000]) } else { msg.clone() });
+                            if write.send(tokio_tungstenite::tungstenite::Message::Text(msg)).await.is_err() {
+                                tracing::error!("Failed to write to websocket");
+                                break;
                             }
                         }
                     });

stub/tests/e2e.rs

@@ -61,7 +61,7 @@ async fn test_full_system_e2e_performance() {
     assert!(stub_exe.exists(), "Stub not found at {:?}", stub_exe);
 
     // 1. Start Server
-    let mut server = ChildGuard(Command::new(&server_exe)
+    let _server = ChildGuard(Command::new(&server_exe)
         .arg("--daemon")
         .env("MCP_PORT", test_port)
         .env("RUST_LOG", "debug")