perf(core): use quanta::Instant for hot-path timing (#2384)

Replace std::time::Instant with quanta::Instant on per-packet, per-RPC,
and per-session paths. TSC-based, ~5ns vs ~25ns per now() call.

Reuses the existing `extern crate self as hotpath` alias so
`use hotpath::instant::Instant;` resolves to the same quanta type with
or without the hotpath feature. Leaves tokio::time::Instant and
smoltcp::time::Instant untouched.

easytier/src/proto/rpc_impl/client.rs

@@ -5,6 +5,7 @@ use std::sync::{Arc, Mutex};
 use bytes::Bytes;
 use dashmap::DashMap;
 use guarden::defer;
+use hotpath::instant::Instant;
 use prost::Message;
 use tokio::sync::mpsc;
 use tokio::task::JoinSet;
@@ -52,7 +53,7 @@ struct InflightRequestKey {
 struct InflightRequest {
     sender: RpcPacketSender,
     merger: PacketMerger,
-    start_time: std::time::Instant,
+    start_time: Instant,
 }
 
 impl std::fmt::Debug for InflightRequest {
@@ -65,14 +66,14 @@ impl std::fmt::Debug for InflightRequest {
 }
 
 #[derive(Debug, Clone, Default)]
-pub struct PeerInfo {
+pub(crate) struct PeerInfo {
     pub peer_id: PeerId,
     pub compression_info: RpcCompressionInfo,
-    pub last_active: Option<std::time::Instant>,
+    pub last_active: Option<Instant>,
 }
 
 type InflightRequestTable = Arc<DashMap<InflightRequestKey, InflightRequest>>;
-pub type PeerInfoTable = Arc<DashMap<PeerId, PeerInfo>>;
+pub(crate) type PeerInfoTable = Arc<DashMap<PeerId, PeerInfo>>;
 
 pub struct Client {
     mpsc: Mutex<MpscTunnel<Box<dyn Tunnel>>>,
@@ -123,7 +124,7 @@ impl Client {
         tasks.spawn(async move {
             loop {
                 tokio::time::sleep(std::time::Duration::from_secs(30)).await;
-                let now = std::time::Instant::now();
+                let now = Instant::now();
                 peer_infos.retain(|_, v| {
                     if let Some(last_active) = v.last_active {
                         return now.duration_since(last_active)
@@ -230,7 +231,7 @@ impl Client {
                 method: <Self::Descriptor as ServiceDescriptor>::Method,
                 input: bytes::Bytes,
             ) -> Result<bytes::Bytes> {
-                let start_time = std::time::Instant::now();
+                let start_time = Instant::now();
                 let transaction_id = CUR_TID.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
                 let (tx, mut rx) = mpsc::unbounded_channel();
                 let key = InflightRequestKey {
@@ -314,7 +315,7 @@ impl Client {
                         PeerInfo {
                             peer_id: self.to_peer_id,
                             compression_info,
-                            last_active: Some(std::time::Instant::now()),
+                            last_active: Some(Instant::now()),
                         },
                     );
 
@@ -385,7 +386,7 @@ impl Client {
         self.inflight_requests.len()
     }
 
-    pub fn peer_info_table(&self) -> PeerInfoTable {
+    pub(crate) fn peer_info_table(&self) -> PeerInfoTable {
         self.peer_info.clone()
     }
 }

easytier/src/proto/rpc_impl/packet.rs

@@ -1,5 +1,7 @@
 use prost::{Message as _, length_delimiter_len};
 
+use hotpath::instant::Instant;
+
 use crate::{
     common::{PeerId, compressor::DefaultCompressor},
     proto::{
@@ -42,10 +44,10 @@ pub async fn decompress_packet(
     Ok(decompressed)
 }
 
-pub struct PacketMerger {
+pub(crate) struct PacketMerger {
     first_piece: Option<RpcPacket>,
     pieces: Vec<RpcPacket>,
-    last_updated: std::time::Instant,
+    last_updated: Instant,
 }
 
 impl Default for PacketMerger {
@@ -59,7 +61,7 @@ impl PacketMerger {
         Self {
             first_piece: None,
             pieces: Vec::new(),
-            last_updated: std::time::Instant::now(),
+            last_updated: Instant::now(),
         }
     }
 
@@ -132,12 +134,12 @@ impl PacketMerger {
             .resize(total_pieces as usize, Default::default());
         self.pieces[piece_idx as usize] = rpc_packet;
 
-        self.last_updated = std::time::Instant::now();
+        self.last_updated = Instant::now();
 
         Ok(self.try_merge_pieces())
     }
 
-    pub fn last_updated(&self) -> std::time::Instant {
+    pub(crate) fn last_updated(&self) -> Instant {
         self.last_updated
     }
 }

easytier/src/proto/rpc_impl/server.rs

@@ -5,6 +5,7 @@ use std::{
 
 use bytes::Bytes;
 use dashmap::DashMap;
+use hotpath::instant::Instant;
 use prost::Message;
 use tokio::{task::JoinSet, time::timeout};
 use tokio_stream::StreamExt;
@@ -233,7 +234,7 @@ impl Server {
         }
 
         let mut resp_msg = RpcResponse::default();
-        let now = std::time::Instant::now();
+        let now = Instant::now();
 
         let compression_info = packet.compression_info;
         let resp_bytes = Self::handle_rpc_request(packet, reg, tunnel_info).await;