Reducing hot-path allocs + duplicate telemetry touchs

Signed-off-by: Alexey <247128645+axkurcom@users.noreply.github.com>

src/proxy/relay.rs

@@ -550,9 +550,7 @@ impl<S: AsyncRead + Unpin> AsyncRead for StatsIo<S> {
                     this.counters.touch(Instant::now(), this.epoch);
 
                     this.stats
-                        .add_user_octets_from_handle(this.user_stats.as_ref(), n_to_charge);
-                    this.stats
-                        .increment_user_msgs_from_handle(this.user_stats.as_ref());
+                        .add_user_traffic_from_handle(this.user_stats.as_ref(), n_to_charge);
                     if this.traffic_lease.is_some() {
                         this.c2s_rate_debt_bytes =
                             this.c2s_rate_debt_bytes.saturating_add(n_to_charge);
@@ -718,9 +716,7 @@ impl<S: AsyncWrite + Unpin> AsyncWrite for StatsIo<S> {
                     this.counters.touch(Instant::now(), this.epoch);
 
                     this.stats
-                        .add_user_octets_to_handle(this.user_stats.as_ref(), n_to_charge);
-                    this.stats
-                        .increment_user_msgs_to_handle(this.user_stats.as_ref());
+                        .add_user_traffic_to_handle(this.user_stats.as_ref(), n_to_charge);
 
                     if let (Some(limit), Some(remaining)) = (this.quota_limit, remaining_before) {
                         if should_immediate_quota_check(remaining, n_to_charge) {

src/stats/mod.rs

@@ -474,6 +474,30 @@ impl Stats {
             .fetch_add(bytes, Ordering::Relaxed);
     }
 
+    #[inline]
+    pub(crate) fn add_user_traffic_from_handle(&self, user_stats: &UserStats, bytes: u64) {
+        if !self.telemetry_user_enabled() {
+            return;
+        }
+        self.touch_user_stats(user_stats);
+        user_stats
+            .octets_from_client
+            .fetch_add(bytes, Ordering::Relaxed);
+        user_stats.msgs_from_client.fetch_add(1, Ordering::Relaxed);
+    }
+
+    #[inline]
+    pub(crate) fn add_user_traffic_to_handle(&self, user_stats: &UserStats, bytes: u64) {
+        if !self.telemetry_user_enabled() {
+            return;
+        }
+        self.touch_user_stats(user_stats);
+        user_stats
+            .octets_to_client
+            .fetch_add(bytes, Ordering::Relaxed);
+        user_stats.msgs_to_client.fetch_add(1, Ordering::Relaxed);
+    }
+
     #[inline]
     pub(crate) fn increment_user_msgs_from_handle(&self, user_stats: &UserStats) {
         if !self.telemetry_user_enabled() {

src/transport/middle_proxy/codec.rs

@@ -5,6 +5,9 @@ use crate::crypto::{AesCbc, crc32, crc32c};
 use crate::error::{ProxyError, Result};
 use crate::protocol::constants::*;
 
+const RPC_WRITER_FRAME_BUF_SHRINK_THRESHOLD: usize = 256 * 1024;
+const RPC_WRITER_FRAME_BUF_RETAIN: usize = 64 * 1024;
+
 /// Commands sent to dedicated writer tasks to avoid mutex contention on TCP writes.
 pub(crate) enum WriterCommand {
     Data(Bytes),
@@ -43,6 +46,7 @@ pub(crate) fn rpc_crc(mode: RpcChecksumMode, data: &[u8]) -> u32 {
     }
 }
 
+/// Builds a fixed-size control payload without heap allocation.
 pub(crate) fn build_control_payload(tag: u32, value: u64) -> [u8; 12] {
     let mut payload = [0u8; 12];
     payload[..4].copy_from_slice(&tag.to_le_bytes());
@@ -51,14 +55,26 @@ pub(crate) fn build_control_payload(tag: u32, value: u64) -> [u8; 12] {
 }
 
 pub(crate) fn build_rpc_frame(seq_no: i32, payload: &[u8], crc_mode: RpcChecksumMode) -> Vec<u8> {
-    let total_len = (4 + 4 + payload.len() + 4) as u32;
-    let mut frame = Vec::with_capacity(total_len as usize);
+    let mut frame = Vec::new();
+    build_rpc_frame_into(&mut frame, seq_no, payload, crc_mode);
+    frame
+}
+
+fn build_rpc_frame_into(
+    frame: &mut Vec<u8>,
+    seq_no: i32,
+    payload: &[u8],
+    crc_mode: RpcChecksumMode,
+) {
+    let total_len = 4 + 4 + payload.len() + 4;
+    frame.clear();
+    frame.reserve(total_len + 15);
+    let total_len = total_len as u32;
     frame.extend_from_slice(&total_len.to_le_bytes());
     frame.extend_from_slice(&seq_no.to_le_bytes());
     frame.extend_from_slice(payload);
     let c = rpc_crc(crc_mode, &frame);
     frame.extend_from_slice(&c.to_le_bytes());
-    frame
 }
 
 pub(crate) async fn read_rpc_frame_plaintext(
@@ -226,29 +242,35 @@ pub(crate) struct RpcWriter {
     pub(crate) iv: [u8; 16],
     pub(crate) seq_no: i32,
     pub(crate) crc_mode: RpcChecksumMode,
+    pub(crate) frame_buf: Vec<u8>,
 }
 
 impl RpcWriter {
     pub(crate) async fn send(&mut self, payload: &[u8]) -> Result<()> {
-        let frame = build_rpc_frame(self.seq_no, payload, self.crc_mode);
+        build_rpc_frame_into(&mut self.frame_buf, self.seq_no, payload, self.crc_mode);
         self.seq_no = self.seq_no.wrapping_add(1);
 
-        let pad = (16 - (frame.len() % 16)) % 16;
-        let mut buf = frame;
+        let pad = (16 - (self.frame_buf.len() % 16)) % 16;
         let pad_pattern: [u8; 4] = [0x04, 0x00, 0x00, 0x00];
         for i in 0..pad {
-            buf.push(pad_pattern[i % 4]);
+            self.frame_buf.push(pad_pattern[i % 4]);
         }
 
         let cipher = AesCbc::new(self.key, self.iv);
         cipher
-            .encrypt_in_place(&mut buf)
+            .encrypt_in_place(&mut self.frame_buf)
             .map_err(|e| ProxyError::Crypto(format!("{e}")))?;
 
-        if buf.len() >= 16 {
-            self.iv.copy_from_slice(&buf[buf.len() - 16..]);
+        if self.frame_buf.len() >= 16 {
+            self.iv
+                .copy_from_slice(&self.frame_buf[self.frame_buf.len() - 16..]);
         }
-        self.writer.write_all(&buf).await.map_err(ProxyError::Io)
+        let write_result = self.writer.write_all(&self.frame_buf).await;
+        if self.frame_buf.capacity() > RPC_WRITER_FRAME_BUF_SHRINK_THRESHOLD {
+            self.frame_buf.clear();
+            self.frame_buf.shrink_to(RPC_WRITER_FRAME_BUF_RETAIN);
+        }
+        write_result.map_err(ProxyError::Io)
     }
 
     pub(crate) async fn send_and_flush(&mut self, payload: &[u8]) -> Result<()> {

src/transport/middle_proxy/pool_writer.rs

@@ -378,6 +378,7 @@ impl MePool {
             iv: hs.write_iv,
             seq_no: 0,
             crc_mode: hs.crc_mode,
+            frame_buf: Vec::new(),
         };
         let writer = MeWriter {
             id: writer_id,

src/transport/middle_proxy/registry.rs

@@ -567,6 +567,29 @@ impl ConnRegistry {
         })
     }
 
+    /// Returns the active writer and routing metadata from one hot-binding lookup.
+    pub async fn get_writer_with_meta(&self, conn_id: u64) -> Option<(ConnWriter, ConnMeta)> {
+        if !self.routing.map.contains_key(&conn_id) {
+            return None;
+        }
+
+        let hot = self.hot_binding.map.get(&conn_id)?;
+        let writer_id = hot.writer_id;
+        let meta = hot.meta.clone();
+        let writer = self
+            .writers
+            .map
+            .get(&writer_id)
+            .map(|entry| entry.value().clone())?;
+        Some((
+            ConnWriter {
+                writer_id,
+                tx: writer,
+            },
+            meta,
+        ))
+    }
+
     pub async fn active_conn_ids(&self) -> Vec<u64> {
         let binding = self.binding.inner.lock().await;
         binding.writer_for_conn.keys().copied().collect()

src/transport/middle_proxy/send.rs

@@ -46,12 +46,6 @@ impl MePool {
         tag_override: Option<&[u8]>,
     ) -> Result<()> {
         let tag = tag_override.or(self.proxy_tag.as_deref());
-        let fallback_meta = ConnMeta {
-            target_dc,
-            client_addr,
-            our_addr,
-            proto_flags,
-        };
         let build_routed_payload = |effective_our_addr: SocketAddr| {
             (
                 build_proxy_req_payload(
@@ -90,16 +84,13 @@ impl MePool {
         let mut hybrid_wait_current = hybrid_wait_step;
 
         loop {
-            let current_meta = self
-                .registry
-                .get_meta(conn_id)
-                .await
-                .unwrap_or_else(|| fallback_meta.clone());
+            if let Some((current, current_meta)) =
+                self.registry.get_writer_with_meta(conn_id).await
+            {
                 let (current_payload, _) = build_routed_payload(current_meta.our_addr);
-            if let Some(current) = self.registry.get_writer(conn_id).await {
                 match current
                     .tx
-                    .try_send(WriterCommand::Data(current_payload.clone()))
+                    .try_send(WriterCommand::Data(current_payload))
                 {
                     Ok(()) => {
                         self.note_hybrid_route_success();
@@ -451,7 +442,7 @@ impl MePool {
                             self.remove_writer_and_close_clients(w.id).await;
                             continue;
                         }
-                        permit.send(WriterCommand::Data(payload.clone()));
+                        permit.send(WriterCommand::Data(payload));
                         self.stats
                             .increment_me_writer_pick_success_try_total(pick_mode);
                         if w.generation < self.current_generation() {
@@ -519,7 +510,7 @@ impl MePool {
                         self.remove_writer_and_close_clients(w.id).await;
                         continue;
                     }
-                    permit.send(WriterCommand::Data(payload.clone()));
+                    permit.send(WriterCommand::Data(payload));
                     self.stats
                         .increment_me_writer_pick_success_fallback_total(pick_mode);
                     if w.generation < self.current_generation() {