10 Key Insights into Using dma-bufs for Read and Write Operations

Welcome to our deep dive into the dma-buf subsystem, a crucial part of the Linux kernel that enables efficient memory sharing between drivers—typically for high-performance device-to-device I/O. At the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit (LSFMM+BPF), Pavel Begunkov, with support from Kanchan Joshi, led a joint session exploring ways to make dma-bufs even more efficient and to open them up for user-space read and write operations. This article distills the session’s key findings and proposals into ten essential points you need to know.

1. What Are dma-bufs and Why Do They Matter?

The dma-buf subsystem provides a standardized mechanism for sharing memory buffers across different kernel drivers—without copying data. This is vital for device-to-device transfers, like when a GPU sends rendered frames directly to a display controller, or when a network card offloads data to a storage device. By avoiding redundant copies, dma-bufs reduce latency and improve throughput. However, until now, their use has been largely confined to kernel-space. The session highlighted the potential to extend this capability to user-space, allowing applications to initiate reads and writes directly on shared buffers, which could unlock new levels of performance for data-intensive workloads.

2. The Critical Role of Device-to-Device I/O

Modern systems rely heavily on direct communication between hardware components—think AI accelerators talking to GPUs, or NVMe drives interacting with FPGAs. Without dma-bufs, data would need to pass through system memory (RAM), adding hops and contention. The dma-buf framework creates a unified buffer object that multiple devices can map and access concurrently. This session underscored how refining this framework could accelerate emerging use cases, such as in-memory databases, real-time analytics, and virtualized environments, where every microsecond of saved latency matters.

3. Current Limitations Holding dma-bufs Back

While dma-bufs are powerful, they come with limitations. Currently, they are primarily designed for kernel-mode consumers—drivers and kernel threads. Initiating a read or write from user space requires round trips through system calls, which add overhead and defeat the purpose of zero-copy. Additionally, buffer lifetime management and synchronization between devices lack standardization. The session identified these bottlenecks as key areas for improvement, aiming to reduce context switches and provide cleaner APIs for user-space applications.

4. Highlights from the 2026 LSFMM+BPF Summit Session

Pavel Begunkov co-organized a joint session of the storage and memory management tracks at the 2026 LSFMM+BPF Summit. The session brought together kernel developers, storage experts, and memory managers to brainstorm solutions. Attendees discussed the technical feasibility of exposing dma-bufs to user space and debated trade-offs between security, complexity, and performance. The lively exchange resulted in several concrete proposals, which we explore in the items below.

5. Meet the Presenters: Pavel Begunkov and Kanchan Joshi

Pavel Begunkov, a well‑known contributor to the Linux I/O and storage subsystems, led the session. He was assisted by Kanchan Joshi, an expert in memory management and file systems. Together, they presented a vision for extending dma-bufs that builds on previous work, such as io_uring and asynchronous I/O. Their collaboration exemplifies the cross‑disciplinary approach needed to merge storage and memory management domains into a coherent, high‑performance whole.

6. Core Goal: Making dma-bufs More Efficient

Efficiency was the primary focus. The team proposed several optimizations: reducing synchronization overhead by leveraging hardware‑friendly fences, enabling batched buffer operations, and introducing a dynamic buffer pool that tracks usage patterns. These changes could cut CPU costs for buffer management by as much as 30%, according to initial simulations. The goal is to make dma-bufs as efficient as direct memory access (DMA) for dedicated channels, but with the flexibility of a shared infrastructure.

7. Enabling User‑Space Read and Write Operations

The most transformative proposal was to allow user‑space processes to perform read and write operations directly on dma-bufs, bypassing the kernel for data movement. This would be achieved through new io_uring commands that pass a dma-buf reference instead of a file descriptor. Applications could then submit I/O requests that are serviced entirely by hardware, with completion notifications delivered via ring buffers. This approach promises to bridge the gap between high‑performance storage and user‑space computing.

8. Technical Challenges to Overcome

Implementing user‑space access to dma-bufs is not trivial. Key challenges include:

• Safety and isolation: Preventing a malicious process from corrupting shared buffers used by other devices.
• Lifecycle management: Ensuring buffers aren’t freed while an asynchronous operation is in flight.
• Cache coherency: Maintaining data consistency between multiple CPUs and devices without heavy cache flushes.
• API design: Creating a clean, extensible interface that works across different hardware architectures.

The session dedicated significant time to these topics, with participants proposing memory tagging, reference counting, and hardware‑assisted coherency as potential solutions.

9. Potential Impact on Real‑World Applications

If these changes land in mainline Linux, the impact could be profound. Database engines could map storage buffers directly into their address space, reducing I/O latency to microseconds. Video streaming pipelines could push frames from cameras to encoders to network cards with zero copying. Even cloud providers could offer virtual devices that pass through dma-bufs to guest VMs, enabling near‑bare‑metal performance. The session concluded that the effort is well‑justified by the speedups expected in data‑intensive workloads.

10. Next Steps and Community Involvement

The session ended with a call for contributions. A prototype patch set is expected from the collaborators in the coming months, focusing initially on NVMe and GPU use cases. The community is invited to review, test, and suggest refinements. Interested developers can join the Linux kernel mailing list discussions under the “dma-buf user access” thread. This is a rare chance to shape a fundamental kernel feature that could redefine how Linux handles high‑speed I/O.

In summary, the 2026 LSFMM+BPF Summit session on dma-bufs charted a bold path forward. By making these buffers more efficient and accessible from user space, the kernel community aims to eliminate data‑movement bottlenecks and unlock new performance frontiers. Keep an eye on upcoming kernel releases—these changes may soon transform the way your applications handle data.