perf(drivers): Use smallvec for AvailBufferToken

src/drivers/fs/virtio_fs.rs

@@ -4,6 +4,7 @@ use alloc::vec::Vec;
 use core::str;
 
 use pci_types::InterruptLine;
+use smallvec::SmallVec;
 use virtio::FeatureBits;
 use virtio::fs::ConfigVolatileFieldAccess;
 use volatile::VolatileRef;
@@ -168,23 +169,26 @@ impl FuseInterface for VirtioFsDriver {
 			payload: cmd_payload_opt,
 		} = cmd;
 		let send = if let Some(cmd_payload) = cmd_payload_opt {
-			vec![
+			SmallVec::from_buf([
 				BufferElem::Sized(cmd_headers),
 				BufferElem::Vector(cmd_payload),
-			]
+			])
 		} else {
-			vec![BufferElem::Sized(cmd_headers)]
+			let mut vec = SmallVec::new();
+			vec.push(BufferElem::Sized(cmd_headers));
+			vec
 		};
 
 		let rsp_headers = Box::<RspHeader<O>, _>::new_uninit_in(DeviceAlloc);
 		let recv = if rsp_payload_len == 0 {
-			vec![BufferElem::Sized(rsp_headers)]
+			let mut vec = SmallVec::new();
+			vec.push(BufferElem::Sized(rsp_headers));
+			vec
 		} else {
-			let rsp_payload = Vec::with_capacity_in(rsp_payload_len as usize, DeviceAlloc);
-			vec![
+			SmallVec::from_buf([
 				BufferElem::Sized(rsp_headers),
-				BufferElem::Vector(rsp_payload),
-			]
+				BufferElem::Vector(Vec::with_capacity_in(rsp_payload_len as usize, DeviceAlloc)),
+			])
 		};
 
 		let buffer_tkn = AvailBufferToken::new(send, recv).unwrap();

src/drivers/net/virtio/mod.rs

@@ -13,6 +13,7 @@ cfg_if::cfg_if! {
 use alloc::boxed::Box;
 use alloc::vec::Vec;
 
+use smallvec::SmallVec;
 use smoltcp::phy::{Checksum, ChecksumCapabilities};
 use smoltcp::wire::{ETHERNET_HEADER_LEN, EthernetFrame, Ipv4Packet, Ipv6Packet};
 use virtio::net::{ConfigVolatileFieldAccess, Hdr, HdrF};
@@ -114,14 +115,14 @@ impl RxQueues {
 fn fill_queue(vq: &mut VirtQueue, num_packets: u16, packet_size: u32) {
 	for _ in 0..num_packets {
 		let buff_tkn = match AvailBufferToken::new(
-			vec![],
-			vec![
+			SmallVec::new(),
+			SmallVec::from_buf([
 				BufferElem::Sized(Box::<Hdr, _>::new_uninit_in(DeviceAlloc)),
 				BufferElem::Vector(Vec::with_capacity_in(
 					packet_size.try_into().unwrap(),
 					DeviceAlloc,
 				)),
-			],
+			]),
 		) {
 			Ok(tkn) => tkn,
 			Err(_vq_err) => {
@@ -292,8 +293,8 @@ impl NetworkDriver for VirtioNetDriver {
 		}
 
 		let buff_tkn = AvailBufferToken::new(
-			vec![BufferElem::Sized(header), BufferElem::Vector(packet)],
-			vec![],
+			SmallVec::from_buf([BufferElem::Sized(header), BufferElem::Vector(packet)]),
+			SmallVec::new(),
 		)
 		.unwrap();
 

src/drivers/virtio/virtqueue/mod.rs

@@ -20,6 +20,7 @@ use core::mem::MaybeUninit;
 use core::{mem, ptr};
 
 use enum_dispatch::enum_dispatch;
+use smallvec::SmallVec;
 use virtio::{le32, le64, pvirtq, virtq};
 
 use self::error::VirtqError;
@@ -396,8 +397,8 @@ impl BufferElem {
 /// respective virtqueue.
 /// The maximum number of descriptors per buffer is bounded by the size of the virtqueue.
 pub struct AvailBufferToken {
-	pub(crate) send_buff: Vec<BufferElem>,
-	pub(crate) recv_buff: Vec<BufferElem>,
+	pub(crate) send_buff: SmallVec<[BufferElem; 2]>,
+	pub(crate) recv_buff: SmallVec<[BufferElem; 2]>,
 }
 
 pub(crate) struct UsedDeviceWritableBuffer {
@@ -450,7 +451,7 @@ impl UsedDeviceWritableBuffer {
 }
 
 pub(crate) struct UsedBufferToken {
-	pub send_buff: Vec<BufferElem>,
+	pub send_buff: SmallVec<[BufferElem; 2]>,
 	pub used_recv_buff: UsedDeviceWritableBuffer,
 }
 
@@ -459,7 +460,7 @@ impl UsedBufferToken {
 		Self {
 			send_buff: tkn.send_buff,
 			used_recv_buff: UsedDeviceWritableBuffer {
-				elems: tkn.recv_buff.into(),
+				elems: tkn.recv_buff.into_vec().into(),
 				remaining_written_len: written_len,
 			},
 		}
@@ -492,7 +493,10 @@ impl AvailBufferToken {
 	/// ```
 	/// they must split the structure after the send part and provide the respective part via the send argument and the respective other
 	/// part via the recv argument.
-	pub fn new(send_buff: Vec<BufferElem>, recv_buff: Vec<BufferElem>) -> Result<Self, VirtqError> {
+	pub fn new(
+		send_buff: SmallVec<[BufferElem; 2]>,
+		recv_buff: SmallVec<[BufferElem; 2]>,
+	) -> Result<Self, VirtqError> {
 		if send_buff.is_empty() && recv_buff.is_empty() {
 			return Err(VirtqError::BufferNotSpecified);
 		}

src/drivers/vsock/mod.rs

@@ -8,6 +8,7 @@ use alloc::vec::Vec;
 use core::mem;
 
 use pci_types::InterruptLine;
+use smallvec::SmallVec;
 use virtio::FeatureBits;
 use virtio::vsock::Hdr;
 
@@ -28,14 +29,14 @@ use crate::mm::device_alloc::DeviceAlloc;
 fn fill_queue(vq: &mut VirtQueue, num_packets: u16, packet_size: u32) {
 	for _ in 0..num_packets {
 		let buff_tkn = match AvailBufferToken::new(
-			vec![],
-			vec![
+			SmallVec::new(),
+			SmallVec::from_buf([
 				BufferElem::Sized(Box::<Hdr, _>::new_uninit_in(DeviceAlloc)),
 				BufferElem::Vector(Vec::with_capacity_in(
 					packet_size.try_into().unwrap(),
 					DeviceAlloc,
 				)),
-			],
+			]),
 		) {
 			Ok(tkn) => tkn,
 			Err(_vq_err) => {
@@ -171,7 +172,15 @@ impl TxQueue {
 				result
 			};
 
-			let buff_tkn = AvailBufferToken::new(vec![BufferElem::Vector(packet)], vec![]).unwrap();
+			let buff_tkn = AvailBufferToken::new(
+				{
+					let mut vec = SmallVec::new();
+					vec.push(BufferElem::Vector(packet));
+					vec
+				},
+				SmallVec::new(),
+			)
+			.unwrap();
 
 			vq.dispatch(buff_tkn, false, BufferType::Direct).unwrap();