BPF and Memory Management: A Q&A on the Future of Controllable Memory Interfaces

At the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit, Roman Gushchin and Shakeel Butt led a discussion on the potential of BPF (Berkeley Packet Filter) for memory management. While many proposals have suggested BPF-based interfaces, none have been merged into the mainline kernel. This session explored why BPF could be transformative, the barriers it faces, and the design requirements for a new BPF-driven memory control group interface. Below, we answer key questions from that discussion.

What role does BPF play in memory management?

BPF, originally a packet filtering tool, has evolved into a general-purpose kernel technology that enables safe, dynamic code execution. In memory management, BPF can be used to create customizable policies for allocating, reclaiming, and controlling memory. It allows developers to write small programs that hook into kernel memory events, such as page faults or memory pressure notifications, and react in real time. This flexibility could replace static kernel logic with user-defined rules, making memory control groups (cgroups) more adaptive. For example, a BPF program could prioritize critical workloads under memory pressure or enforce per-process limits without recompiling the kernel. However, integrating BPF into the memory management path requires careful handling of concurrency, atomicity, and kernel stability concerns.

What obstacles prevent BPF-based memory management from reaching the mainline?

Several technical and design hurdles have blocked BPF-based memory management proposals. First, memory management code runs in performance-sensitive paths where any overhead is unacceptable; BPF programs must be extremely efficient. Second, kernel memory operations often involve complex locking and memory ordering semantics that BPF's verifier cannot fully model. This makes it difficult to ensure that a BPF program doesn't introduce deadlocks or data races. Third, existing BPF helpers lack adequate support for memory-specific operations, such as inspecting page flags or adjusting cgroup counters atomically. Finally, there is no standardized interface for BPF programs to communicate with memory management subsystems like the page allocator or reclaim logic. These obstacles require either extending BPF's capabilities or redesigning how kernel memory functions expose hooks.

What did Roman Gushchin propose for BPF and memory management?

Roman Gushchin, a leading kernel memory management developer, proposed a session to map out how BPF could be practically applied. He highlighted that while many attempts had been submitted, none accounted for the unique constraints of memory management. Gushchin suggested focusing on specific, low-risk use cases first, such as monitoring memory usage patterns or triggering custom actions on memory pressure events. He also advocated for incremental additions rather than a monolithic BPF interface. For instance, adding a BPF hook to the memory reclaim path that could filter which pages to evict based on user-defined policies. Gushchin emphasized the need for a rigorous verifier update to trust BPF programs in safety-critical memory paths.

What are Shakeel Butt's requirements for a new BPF-based memory control group interface?

Shakeel Butt led a follow-up discussion on designing a BPF-driven interface for memory control groups (cgroups). His key requirements included simplicity: the interface must be easy to understand and use, avoiding complex BPF programs for common tasks. Performance: any BPF hook must have minimal overhead, ideally adding less than 1% to memory management operations. Safety: the kernel must ensure that BPF programs cannot crash or hang the system, which means the verifier needs new rules for memory paths. Composability: multiple BPF programs should be able to coexist without interference. Backward compatibility: existing cgroup memory controllers should remain unchanged, with BPF as an optional enhancement. Butt also stressed the importance of thorough testing and a clear documentation of BPF helper functions for memory operations.

What potential use cases could benefit from BPF in memory management?

Multiple use cases were discussed at the summit. One prominent example is dynamic priority management: using BPF to adjust memory limits or reclaim priorities for containers based on real-time metrics like latency or throughput. Another is custom OOM (Out-Of-Memory) handling: instead of the kernel's generic OOM killer, a BPF program could select the best process to terminate based on application-level semantics. Memory accounting enhancements are also possible, allowing BPF to track per-page or per-slab allocations beyond standard cgroup counters. Additionally, BPF could be used for proactive memory defragmentation: triggering compaction when fragmentation crosses a threshold defined by user policies. Finally, debugging and profiling memory behavior becomes easier with BPF programs that log page faults, swap events, or slab allocations without kernel modifications.

What are the next steps for integrating BPF into memory management?

Following the session, the community agreed on several actionable steps. First, a working group will draft a set of BPF helper functions specific to memory management, such as helpers to query page flags or cgroup memory pressure levels. Second, the BPF verifier will be extended to handle memory-related invariants, like ensuring that a BPF program does not hold a spinlock while accessing user memory. Third, a prototype hook in the reclaim path will be implemented to test performance and correctness. Finally, a new BPF program type for memory management (e.g., BPF_PROG_TYPE_MEM_CGROUP) will be proposed to the kernel mailing list. These incremental steps aim to gather real-world feedback before considering a full merge. The goal is to have a minimal but safe BPF interface in mainline within two kernel releases.