Free tools Windows power users keep installed
One-click scans. No signup required.
The proposed vhost zero-copy receive design would let a physical NIC DMA packet data into buffers allocated for a virtio-net guest, avoiding the usual payload copy from a host receive buffer into a guest buffer. It is a specialized architecture—not a generic receive mode you can assume is available on a current Linux installation. Its feasibility depends on the kernel, backend, NIC driver, and distribution.
How the proposed receive path works
The design spans virtio-net, vhost-net, macvtap, and the physical NIC driver. Instead of receiving a packet into an ordinary host buffer and then copying its payload into a guest buffer, it passes guest-backed buffers down to the NIC for DMA.
- virtio-net allocates buffers. The guest receive buffers must be page-size-aligned and suitable for DMA. The proposal adds an
add_recvbuf_full_page()path because the existing virtio-net receive-buffer helpers did not guarantee page alignment. - vhost-net posts the buffers to macvtap. A proposed
MSG_ZCOPY_RX_POSTcontrol flag carries the guest buffers down the receive path. - macvtap connects them to the physical NIC. It maps the buffers into an skb and passes them to the driver using the proposed
ndo_post_rx_buffer()operation. A separate proposedndo_set_zerocopy_rx()callback binds virtual and physical queues. - The NIC DMA-writes the packet into guest memory. The driver places the posted buffers on its receive descriptor ring. When a packet arrives, the NIC writes its data directly into one of those buffers.
- The receive completion returns through the stack. macvtap queues the skb and identifies the completed virtio descriptor; vhost-net updates the virtqueue. The proposed
MSG_ZCOPY_RXflag marks the preallocated buffers on the receive side.
These callback and control-message names describe additions in the proposal; they should not be read as evidence that ordinary Linux kernels expose or enable this path.
What “zero-copy” means here
Zero-copy refers to avoiding the payload memcpy between a host receive buffer and a guest virtio buffer. It does not eliminate buffer allocation, skb tracking, mappings, DMA ownership changes, or virtqueue completion and synchronization. The design document also identifies the absence of a unified receive-memory allocation mechanism as an issue.
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
Is vhost zero-copy receive supported on current systems?
The available status evidence does not establish a generally enabled vhost zero-copy receive mode for current installations. Treat this as a proposed receive architecture unless a specific kernel, backend, driver, and distribution document or implement it.
Do not confuse it with historical vhost-net transmit zero-copy
Linux vhost-net historically included zerocopy TX fields and completion handling. That was a send-side path, not the receive design described above. In a 2025 kernel mailing-list patch, author Jon Kohler proposed removing it: the path had been disabled by default since 2019, skb orphaning could force a copy, its outstanding zerocopy budget was often exhausted, and the patch cited no tangible benefit. The patch removed 398 lines from drivers/vhost/net.c. Red Hat’s RHEL 7 virtualization guide also documented vhost-net zero-copy as disabled by default; that historical statement does not establish the defaults of other distributions or current releases.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
For context only, the historical TX source used a maximum of 128 outstanding pending entries and a 256-byte threshold when selecting zerocopy. Those are implementation constants for that TX code, not limits, thresholds, or performance guarantees for the proposed receive architecture.
How this differs from MSG_ZEROCOPY
| Mechanism | Direction and purpose | What to keep in mind |
|---|---|---|
| Proposed vhost zero-copy receive | Receive: posts guest buffers toward a physical NIC so it can DMA packet data into guest memory. | Requires the proposed receive-path integration across virtio-net, vhost-net, macvtap, and a compatible NIC driver; it is not evidence of a generic enabled mode. |
Linux MSG_ZEROCOPY |
Send: asks socket send calls to avoid copying data. Linux documentation describes support for TCP, UDP, and VSOCK with virtio transport. | Page pinning trades per-byte copy cost for page-accounting and completion-notification overhead. The Linux kernel documentation’s rule of thumb is that it generally becomes effective only for writes over around 10 KB; that is a send-side guideline, not an RX threshold. |
What to verify before evaluating an implementation
A no-copy data path is not, by itself, proof of better throughput or lower CPU use. There is no authoritative receive benchmark established for this proposal, so measure against ordinary copy-based vhost receive on the exact target system.
Recommended Free Tools
Quick Recap
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
- Confirm that the specific kernel and distribution implement the receive design, and that the selected backend and NIC driver support its required callbacks and control path.
- Verify page alignment, DMA suitability, IOMMU and DMA-mapping behavior, and correct ownership transitions for the buffers.
- Check how the implementation handles buffer lifetime, skb management, queue binding, completion signaling, and synchronization under load.
- Compare payload-copy counts, throughput, and CPU cost under the target workload; account for allocation, mapping, and completion overhead rather than inferring a win from the architecture.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
