mm, bpf: BPF based THP order selection #5651
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This patch introduces a new BPF struct_ops called bpf_thp_ops for dynamic THP tuning. It includes a hook get_suggested_order() [0], allowing BPF programs to influence THP order selection based on factors such as: - Workload identity For example, workloads running in specific containers or cgroups. - Allocation context Whether the allocation occurs during a page fault, khugepaged, or other paths. - System memory pressure (May require new BPF helpers to accurately assess memory pressure.) Key Details: - Only one BPF program can be attached at a time, but it can be updated dynamically to adjust the policy. - Supports automatic mTHP order selection and per-workload THP policies. - Only functional when THP is set to madise or always. Experimental Status: - Requires CONFIG_EXPERIMENTAL_BPF_ORDER_SELECTION to enable. [1] - This feature is unstable and may evolve in future kernel versions. Link: https://lwn.net/ml/all/[email protected]/ [0] Link: https://lwn.net/ml/all/[email protected]/ [1] Suggested-by: David Hildenbrand <[email protected]> Suggested-by: Lorenzo Stoakes <[email protected]> Signed-off-by: Yafang Shao <[email protected]>
We will utilize this new kfunc bpf_mm_get_mem_cgroup() to retrieve the associated mem_cgroup from the given @mm. The obtained mem_cgroup must be released by calling bpf_put_mem_cgroup() as a paired operation. Signed-off-by: Yafang Shao <[email protected]>
We will utilize this new kfunc bpf_mm_get_task() to retrieve the associated task_struct from the given @mm. The obtained task_struct must be released by calling bpf_task_release() as a paired operation. Signed-off-by: Yafang Shao <[email protected]>
This self-test verifies that PMD-mapped THP allocation is restricted in page faults for tasks within a specific cgroup, while still permitting THP allocation via khugepaged. Since THP allocation depends on various factors (e.g., system memory pressure), using the actual allocated THP size for validation is unreliable. Instead, we check the return value of get_suggested_order(), which indicates whether the system intends to allocate a THP, regardless of whether the allocation ultimately succeeds. Signed-off-by: Yafang Shao <[email protected]>
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Upstream branch: cd7c97f |
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=986661 expired. Closing PR. |
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Pull request for series with
subject: mm, bpf: BPF based THP order selection
version: 4
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=986661