Memory Controller eBPF support #6391
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Add eBPF struct ops support to the memory controller, enabling dynamic memory management policies via eBPF programs. This allows users to implement custom memory charging and reclamation strategies without kernel recompilation. The implementation introduces: - A new BPF struct ops type `memcg_ops` with a `try_charge_memcg` hook for intercepting memory charge operations - Integration into the `try_charge_memcg()` function to call registered eBPF handlers - Safe registration/unregistration via BPF struct ops infrastructure - Reference counting using percpu_ref to track handler lifecycle - Static branch keys to minimize overhead when disabled - New Kconfig option CONFIG_MEMCG_BPF to control the feature The eBPF handler receives a `try_charge_memcg` struct containing: - Memory cgroup and affected memory cgroup - GFP flags and page count - Reclamation options - Current charge status Handlers can inspect this context and modify certain fields (e.g., nr_pages) to adjust reclamation behavior. The design enforces single active handler to avoid conflicts. Use cases include: - Custom memory policies for specialized workloads - Memory pressure telemetry and monitoring - Integration with container management systems - Runtime memory management experimentation Design decisions: - Uses RCU synchronization for safe handler replacement - Zero overhead when feature is disabled (via static keys) - Single handler model prevents complexity and race conditions - eBPF verifier restrictions ensure memory safety - Minimal context exposure to reduce attack surface Signed-off-by: Geliang Tang <[email protected]> Signed-off-by: Hui Zhu <[email protected]>
Add comprehensive selftest suite for memory controller eBPF support. The tests validate the core functionality of the memcg_ops struct ops implementation. Test coverage includes: 1. test_memcg_ops_load: Validates that the eBPF object file can be successfully loaded by libbpf. 2. test_memcg_ops_attach: Tests attaching the memcg_ops struct ops to the kernel, verifying the basic attachment mechanism works correctly. 3. test_memcg_ops_double_attach: Validates that only one memcg_ops instance can be attached at a time. Attempts to attach a second program should fail, ensuring the single-handler design constraint is enforced. The test suite includes: - prog_tests/memcg_ops.c: Test entry point with individual test functions using standard BPF test framework helpers like ASSERT_OK_PTR and ASSERT_ERR_PTR - progs/memcg_ops.bpf.c: Simple eBPF program implementing the struct ops interface Uses standard test_progs framework macros for consistent error reporting and handling. All tests properly clean up resources in error paths. Signed-off-by: Geliang Tang <[email protected]> Signed-off-by: Hui Zhu <[email protected]>
Add a sample eBPF program demonstrating the new memory controller eBPF support. This example serves as both a reference implementation and a validation tool for the memcg eBPF functionality. The sample includes: - memcg_printk.bpf.c: An eBPF program that attaches to the try_charge_memcg hook and prints detailed information about memory charging events, including: * Memory cgroup name * GFP flags and page count * Reclamation options * Affected memory cgroup (when applicable) - memcg_printk.c: A userspace loader program that: * Loads the eBPF object file * Finds and attaches the memcg_ops struct ops * Keeps the program attached until interrupted * Provides proper error handling and cleanup Usage: $ ./samples/bpf/memcg_printk This will attach the eBPF program to the memcg charging path. Output can be viewed via kernel trace events (e.g., trace_printk logs). The program demonstrates: - Accessing memory cgroup context fields - Using bpf_printk for debugging and monitoring - Proper struct ops registration via libbpf - Integration with the kernel's BPF infrastructure Signed-off-by: Geliang Tang <[email protected]> Signed-off-by: Hui Zhu <[email protected]>
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Upstream branch: d6ec090 |
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=1025066 expired. Closing PR. |
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Pull request for series with
subject: Memory Controller eBPF support
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1025066