quic: use smallvec to aggregate chunks, save 1 alloc per packet (#735)

quic: use smallvec, save one allocation per packet

Use smallvec to hold chunks. Streams are packet-sized so we don't expect
them to have many chunks. This saves us an allocation for each packet.

Cargo.lock

@@ -5257,9 +5257,9 @@ checksum = "9def91fd1e018fe007022791f865d0ccc9b3a0d5001e01aabb8b40e46000afb5"
 
 [[package]]
 name = "smallvec"
-version = "1.13.1"
+version = "1.13.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e6ecd384b10a64542d77071bd64bd7b231f4ed5940fba55e98c3de13824cf3d7"
+checksum = "3c5e1a9a646d36c3599cd173a41282daf47c44583ad367b8e6837255952e5c67"
 
 [[package]]
 name = "smpl_jwt"
@@ -7288,6 +7288,7 @@ dependencies = [
  "quinn-proto",
  "rand 0.8.5",
  "rustls",
+ "smallvec",
  "solana-logger",
  "solana-measure",
  "solana-metrics",

Cargo.toml

@@ -304,7 +304,7 @@ sha2 = "0.10.8"
 sha3 = "0.10.8"
 signal-hook = "0.3.17"
 siphasher = "0.3.11"
-smallvec = "1.13.1"
+smallvec = "1.13.2"
 smpl_jwt = "0.7.1"
 socket2 = "0.5.6"
 soketto = "0.7"

programs/sbf/Cargo.lock

@@ -4548,9 +4548,9 @@ checksum = "c111b5bd5695e56cffe5129854aa230b39c93a305372fdbb2668ca2394eea9f8"
 
 [[package]]
 name = "smallvec"
-version = "1.13.1"
+version = "1.13.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e6ecd384b10a64542d77071bd64bd7b231f4ed5940fba55e98c3de13824cf3d7"
+checksum = "3c5e1a9a646d36c3599cd173a41282daf47c44583ad367b8e6837255952e5c67"
 
 [[package]]
 name = "smpl_jwt"
@@ -6331,6 +6331,7 @@ dependencies = [
  "quinn-proto",
  "rand 0.8.5",
  "rustls",
+ "smallvec",
  "solana-measure",
  "solana-metrics",
  "solana-perf",

streamer/Cargo.toml

@@ -26,6 +26,7 @@ quinn = { workspace = true }
 quinn-proto = { workspace = true }
 rand = { workspace = true }
 rustls = { workspace = true, features = ["dangerous_configuration"] }
+smallvec = { workspace = true }
 solana-measure = { workspace = true }
 solana-metrics = { workspace = true }
 solana-perf = { workspace = true }

streamer/src/nonblocking/quic.rs

@@ -18,6 +18,7 @@ use {
     quinn::{Connecting, Connection, Endpoint, EndpointConfig, TokioRuntime, VarInt},
     quinn_proto::VarIntBoundsExceeded,
     rand::{thread_rng, Rng},
+    smallvec::SmallVec,
     solana_measure::measure::Measure,
     solana_perf::packet::{PacketBatch, PACKETS_PER_BATCH},
     solana_sdk::{
@@ -96,7 +97,7 @@ struct PacketChunk {
 // the Packet and then when copying the Packet into a PacketBatch)
 struct PacketAccumulator {
     pub meta: Meta,
-    pub chunks: Vec<PacketChunk>,
+    pub chunks: SmallVec<[PacketChunk; 2]>,
     pub start_time: Instant,
 }
 
@@ -934,7 +935,7 @@ async fn handle_chunk(
                     meta.set_from_staked_node(matches!(peer_type, ConnectionPeerType::Staked(_)));
                     *packet_accum = Some(PacketAccumulator {
                         meta,
-                        chunks: Vec::new(),
+                        chunks: SmallVec::new(),
                         start_time: Instant::now(),
                     });
                 }
@@ -1543,7 +1544,7 @@ pub mod test {
             meta.size = size;
             let packet_accum = PacketAccumulator {
                 meta,
-                chunks: vec![PacketChunk {
+                chunks: smallvec::smallvec![PacketChunk {
                     bytes,
                     offset,
                     end_of_chunk: size,