Linux 7.3 Boosts FUSE Performance with Buffer Groups and Zero-Copy

**FUSE, the technology that allows file systems to be executed from user space, may incorporate buffer groups for IO_uring and zero-copy capabilities in Linux 7.3. The changes aim to enhance performance, reduce memory consumption, and avoid unnecessary data movements.

• The development of Linux 7.3 adds buffer groups for IO_uring in FUSE.
• Zero-copy aims to avoid copies between the kernel and user space; its implementation requires buffer groups and may depend on specific privileges.
• Tests cited in the patch series report performance improvements, although the results do not represent all FUSE workloads.

FUSE, the Linux kernel component that allows building and executing file systems from user space, is heading towards a significant performance improvement with Linux 7.3. The version is still under development and incorporates advancements for IO_uring transport that aim to reduce memory consumption and accelerate data exchange between the kernel and FUSE servers.

A report from Phoronix published on August 26, 2026, indicates that the main optimizations are compatibility with IO_uring buffer groups and the incorporation of zero-copy mechanisms. The work also includes bug fixes and other adjustments. The documentation and available patch series describe these functions as part of the FUSE development, so their details may still change before a stable version.

A More Flexible Buffer Management

The previous architecture of FUSE maintained a close relationship between each request entry and its payload buffer. In practice, this could require independent buffers and sufficient capacity for the maximum possible payload size, even when requests used far fewer bytes.

The patch series attributed to Joanne Koong suggests that this design is suboptimal because some classes of requests require little data, while others do not need any payload buffer. The scheme could reserve memory above the actual needs of each operation, a limitation especially important in scenarios with numerous simultaneous requests.

Buffer groups change that relationship by allowing the server to pre-register buffers and for the kernel to use them according to the needs of the entries and requests. Thus, entries are no longer tied to a dedicated buffer, and the kernel gains greater freedom to distribute payload memory among active operations.

This decoupling can reduce the memory requirements needed to use FUSE over IO_uring and opens the door to new optimizations in resource allocation. The advantage lies not only in reserving less space but also in allowing memory usage to adapt to the specific nature of each request.

Zero-Copy Avoids Intermediate Steps

The same line of work adds zero-copy support to the IO_uring transport of FUSE. With this mechanism, the server can directly access pages from the client or pages from the page cache, without first transferring the data to an intermediate buffer.

Eliminating that copy can reduce the work associated with data movement and improve the efficiency of input and output operations. The benefit is particularly attractive for workloads that handle large volumes of information, although the available tests do not establish a universal performance figure applicable to all systems or applications.

The function will not be available without restrictions: the documentation related to FUSE passthrough indicates that certain modes require the CAP_SYS_ADMIN privilege, while the zero-copy series requires enabling kernel-managed buffer groups. These security and configuration conditions must be evaluated before considering the mechanism for production environments.

Operationally, the combination of buffer groups and zero-copy provides the kernel with more control over memory and reduces the number of steps needed to handle certain requests. However, the final outcome will depend on the implementation of the FUSE server, the data access pattern, and the system privilege configuration.

Tests Show Improvements in FUSE

Joanne Koong conducted benchmark tests to measure the effect of the proposed changes. According to the results cited in the patch series and by Phoronix, some direct random reads recorded an approximate 20% increase in performance, from around 2,100 MB/s. This figure corresponds to a specific test and does not necessarily represent the behavior of all FUSE modes.

The interest in these results lies in the fact that FUSE is used to implement file systems without placing all its logic within the kernel. This flexibility facilitates the development and integration of services, but it can also introduce costs arising from communication between user space, the kernel, and the memory areas involved in each operation.

By addressing buffer allocation and data copies, Linux 7.3 aims to reduce two potential sources of overhead in that path. The improvement may translate into a more efficient response for applications that rely on FUSE file systems, although developers and administrators will need to check the impact on their own workflows.

In addition to these IO_uring optimizations, the development includes bug fixes and other changes to the FUSE code. The available information does not detail each adjustment but presents them as part of the set of modifications accompanying the evolution of this functionality.

Support for Large Pages Still Pending

The work on FUSE also includes preparations to support large pages, an evolution related to how the kernel manages memory pages. However, this capability is still not finished and is not part of a complete implementation ready for general use.

The distinction is important because preparations do not equate to a finalized function. For now, the described progress focuses on IO_uring buffer groups, zero-copy, bug fixes, and complementary changes included in the FUSE development.

Thus, Linux 7.3 continues as an evolving platform, and its details may change before the final version. Users interested in adopting the new features should follow the kernel development and validate the compatibility of their FUSE servers, especially when relying on CAP_SYS_ADMIN or specific IO_uring configurations.

The project's direction is to make FUSE use memory more rationally and to require less additional work for data exchange. If the improvements observed in the tests hold, the update could provide a faster and more efficient foundation for file systems implemented in user space.