Merge pull request #1693 from Gelbpunkt/num_buffers_1

perf(virtio-net): Don't copy packets when num_buffers is 1

Author: mkroening

src/drivers/net/gem.rs

@@ -340,7 +340,7 @@ impl NetworkDriver for GEMDriver {
 				};
 				trace!("BUFFER: {buffer:x?}");
 				self.rx_buffer_consumed(index as usize);
-				Some((RxToken::new(buffer.to_vec()), TxToken::new()))
+				Some((RxToken::new(buffer.to_vec_in(DeviceAlloc)), TxToken::new()))
 			}
 			None => None,
 		}

src/drivers/net/rtl8139.rs

@@ -3,6 +3,7 @@
 #![allow(dead_code)]
 
 use alloc::boxed::Box;
+use alloc::vec::Vec;
 use core::mem;
 
 use memory_addresses::VirtAddr;
@@ -17,6 +18,7 @@ use crate::drivers::error::DriverError;
 use crate::drivers::net::NetworkDriver;
 use crate::drivers::pci::PciDevice;
 use crate::executor::device::{RxToken, TxToken};
+use crate::mm::device_alloc::DeviceAlloc;
 
 /// size of the receive buffer
 const RX_BUF_LEN: usize = 8192;
@@ -287,14 +289,18 @@ impl NetworkDriver for RTL8139Driver {
 		let length = self.rx_peek_u16() - 4; // copy packet (but not the CRC)
 		let pos = (self.rxpos + mem::size_of::<u16>()) % RX_BUF_LEN;
 
+		let mut vec_data = Vec::with_capacity_in(length as usize, DeviceAlloc);
+
 		// do we reach the end of the receive buffers?
 		// in this case, we contact the two slices to one vec
-		let vec_data = if pos + length as usize > RX_BUF_LEN {
+		if pos + length as usize > RX_BUF_LEN {
 			let first = &self.rxbuffer[pos..RX_BUF_LEN];
 			let second = &self.rxbuffer[..length as usize - first.len()];
-			[first, second].concat()
+
+			vec_data.extend_from_slice(first);
+			vec_data.extend_from_slice(second);
 		} else {
-			(self.rxbuffer[pos..][..length.into()]).to_vec()
+			vec_data.extend_from_slice(&self.rxbuffer[pos..][..length.into()]);
 		};
 
 		self.consume_current_buffer();

src/drivers/net/virtio/mod.rs

@@ -305,13 +305,17 @@ impl NetworkDriver for VirtioNetDriver {
 	}
 
 	fn receive_packet(&mut self) -> Option<(RxToken, TxToken)> {
-		let mut buffer_tkn = self.recv_vqs.get_next()?;
-		RxQueues::post_processing(&mut buffer_tkn)
-			.inspect_err(|vnet_err| warn!("Post processing failed. Err: {vnet_err:?}"))
-			.ok()?;
-		let first_header = buffer_tkn.used_recv_buff.pop_front_downcast::<Hdr>()?;
-		let first_packet = buffer_tkn.used_recv_buff.pop_front_vec()?;
-		trace!("Header: {first_header:?}");
+		let mut receive_single_packet = || {
+			let mut buffer_tkn = self.recv_vqs.get_next()?;
+			RxQueues::post_processing(&mut buffer_tkn)
+				.inspect_err(|vnet_err| warn!("Post processing failed. Err: {vnet_err:?}"))
+				.ok()?;
+			let header = buffer_tkn.used_recv_buff.pop_front_downcast::<Hdr>()?;
+			let packet = buffer_tkn.used_recv_buff.pop_front_vec()?;
+			Some((header, packet))
+		};
+
+		let (first_header, first_packet) = receive_single_packet()?;
 
 		// According to VIRTIO spec v1.2 sec. 5.1.6.3.2, "num_buffers will always be 1 if VIRTIO_NET_F_MRG_RXBUF is not negotiated."
 		// Unfortunately, NVIDIA MLX5 does not comply with this requirement and we have to manually set the value to the correct one.
@@ -321,17 +325,11 @@ impl NetworkDriver for VirtioNetDriver {
 			1
 		};
 
-		let mut packets = Vec::with_capacity(num_buffers.into());
-		packets.push(first_packet);
+		let mut combined_packets = first_packet;
 
 		for _ in 1..num_buffers {
-			let mut buffer_tkn = self.recv_vqs.get_next().unwrap();
-			RxQueues::post_processing(&mut buffer_tkn)
-				.inspect_err(|vnet_err| warn!("Post processing failed. Err: {vnet_err:?}"))
-				.ok()?;
-			let _header = buffer_tkn.used_recv_buff.pop_front_downcast::<Hdr>()?;
-			let packet = buffer_tkn.used_recv_buff.pop_front_vec()?;
-			packets.push(packet);
+			let (_header, packet) = receive_single_packet()?;
+			combined_packets.extend_from_slice(&packet);
 		}
 
 		fill_queue(
@@ -340,9 +338,7 @@ impl NetworkDriver for VirtioNetDriver {
 			self.recv_vqs.packet_size,
 		);
 
-		let vec_data = packets.into_iter().flatten().collect();
-
-		Some((RxToken::new(vec_data), TxToken::new()))
+		Some((RxToken::new(combined_packets), TxToken::new()))
 	}
 
 	fn set_polling_mode(&mut self, value: bool) {

src/executor/device.rs

@@ -23,6 +23,7 @@ use crate::arch::kernel::mmio as hardware;
 use crate::drivers::net::NetworkDriver;
 #[cfg(feature = "pci")]
 use crate::drivers::pci as hardware;
+use crate::mm::device_alloc::DeviceAlloc;
 
 /// Data type to determine the mac address
 #[derive(Debug, Clone)]
@@ -220,11 +221,11 @@ pub(crate) type RxHandle = usize;
 
 #[doc(hidden)]
 pub(crate) struct RxToken {
-	buffer: Vec<u8>,
+	buffer: Vec<u8, DeviceAlloc>,
 }
 
 impl RxToken {
-	pub(crate) fn new(buffer: Vec<u8>) -> Self {
+	pub(crate) fn new(buffer: Vec<u8, DeviceAlloc>) -> Self {
 		Self { buffer }
 	}
 }