BPF in Memory Management: Challenges and Pathways to Integration

At the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit, Roman Gushchin initiated a discussion on why numerous proposals to integrate BPF (Berkeley Packet Filter) into memory management have not been accepted into the mainline kernel. Despite the potential benefits, these proposals face significant obstacles. The session, followed by a talk from Shakeel Butt, aimed to identify the core requirements for a new BPF-based interface for memory control groups. This Q&A explores the key questions raised during these discussions.

1. What specific BPF-based memory management proposals have been made, and why have none been merged?

Several proposals have emerged over the years, each attempting to leverage BPF's flexibility for fine-grained memory control. For example, some suggested using BPF programs to dynamically adjust memory allocation policies or to monitor and throttle memory usage in real time. Others aimed to replace traditional cgroup memory controllers with BPF-based hooks. However, none have made it into the mainline kernel. The primary reason is the complexity of memory management itself—unlike networking, where BPF excels, memory operations are deeply integrated with kernel internals and involve locking, page reclaim, and direct memory access. Any BPF program injected here could cause subtle bugs or performance regressions. Additionally, the kernel maintainers have concerns about security and maintainability; a faulty BPF program in the memory path could crash the system or corrupt data. The lack of a clear, stable API for memory-controlling BPF also remains a barrier.

BPF in Memory Management: Challenges and Pathways to Integration

2. How could BPF potentially improve memory management if the obstacles were overcome?

BPF's programmability offers a unique opportunity for dynamic and user-defined memory policies. For instance, administrators could write BPF programs to fine-tune memory pressure thresholds based on application behavior, or to selectively reclaim memory from specific cgroups when resource contention arises. It could also enable real-time accounting and throttling of memory usage without the overhead of periodic polling. In cloud environments, BPF might allow tenants to customize memory management for their workloads—for example, enforcing guaranteed memory minimums or proportional sharing. Moreover, BPF’s safety features, such as verifier checks and sandboxed execution, could reduce the risk of kernel crashes compared to loading opaque kernel modules. The main value proposition is flexibility without sacrificing performance, as BPF programs run in kernel context with minimal overhead. However, these benefits can only be realized if the interface is designed to avoid deadlock and interference with core memory subsystems.

3. What were the key obstacles raised by Roman Gushchin during his session?

Roman Gushchin highlighted several hurdles that have stalled BPF adoption in memory management. First, memory management is inherently stateful and time-sensitive—unlike packet processing, where BPF operates on discrete events, memory decisions often depend on global system state and require precise timing. Introducing BPF hooks in paths like page reclaim or allocation could lead to unpredictable delays or deadlocks. Second, the verifier limitations pose a problem; BPF programs must be proven safe, but memory-related operations involve complex data structures (e.g., LRU lists, slab caches) that are difficult to analyze statically. Third, there is reluctance from memory management maintainers to complicate a subsystem that is already challenging to debug. Any BPF interface must be carefully scoped to avoid breaking longstanding assumptions. Finally, Gushchin noted that existing cgroup memory controllers work well for most use cases, reducing the urgency to add BPF capabilities unless clear, compelling advantages are demonstrated.

4. What requirements for a BPF-based memory control group interface did Shakeel Butt propose?

Shakeel Butt, who led the follow-up discussion, outlined several essential requirements for a new BPF-based interface for memory cgroups. First, the interface must not degrade performance of normal memory operations; BPF hooks should be lightweight and only invoked when necessary. Second, it should ensure isolation between cgroups, preventing one tenant’s BPF program from affecting another’s memory limits. Third, the design must avoid circular dependencies—for example, a BPF program that allocates memory while handling a memory event could cause deadlocks. Fourth, the API should be stable and backward-compatible, allowing existing cgroup memory management to continue working without BPF. Fifth, it should provide clear error semantics; if a BPF program fails, the system must fall back to a safe default behavior. Finally, Butt emphasized the need for comprehensive testing infrastructure to catch regressions early. These requirements aim to build a bridge between BPF’s flexibility and the robustness demanded by memory management.

5. How does the memory management track differ from networking, where BPF has seen widespread adoption?

BPF’s success in networking stems from the nature of packet processing: each packet is an independent event, and BPF programs operate on a per-packet basis with strict time limits. Memory management, by contrast, involves global state and complex interactions between processes, cgroups, and kernel memory reclaim. A memory allocation or page reclaim decision can affect system-wide latency and fairness. In networking, BPF programs are often used for filtering, forwarding, or load balancing—operations that can be safely offloaded without breaking core kernel invariants. In memory management, any BPF hook that modifies the reclaim path or allocation policy risks deadlock or priority inversion. Additionally, networking BPF programs are typically stateless or use per-CPU maps, whereas memory management requires access to shared data structures protected by locks. The kernel community has therefore approached memory-related BPF with caution, demanding rigorous proofs of safety and performance guarantees that are still being developed.

6. What are the next steps toward making BPF a viable tool for memory control?

Moving forward, the key steps include prototyping a minimal, safe BPF hook—for example, only allowing read-only introspection of memory counters, then gradually expanding to controlled actions. Proposed next steps are:

Define a clear set of allowed BPF helper functions that avoid dangerous memory operations.
Create simulation or emulation environments to test BPF programs against extreme memory pressure scenarios.
Engage the memory management and BPF maintainers in a joint design review to agree on API boundaries.
Develop benchmarks that quantify the overhead of BPF hooks compared to traditional cgroup controllers.
Explore kernel-hardening techniques to mitigate risks from malicious or buggy BPF programs in memory paths.

These efforts aim to eventually produce a patch series that can be incrementally merged into the mainline, similar to how BPF was gradually introduced into other kernel subsystems. The community remains optimistic but recognizes that memory management requires a more cautious approach.

Tags: