Configuring Linux Kernel Memory Page Allocations (3820)

Technical Overview

Modern eBPF programs—especially those attached to XDP, TC, or cgroup hooks—often allocate and free memory pages at line rate. The default Linux page allocator (buddy system) is tuned for general‑purpose workloads and can become a bottleneck when thousands of BPF maps, ring buffers, or socket buffers are created per second.

This article walks through the kernel page allocation subsystem (zone watermarks, per‑CPU page caches, compaction, and hugepage pools) and shows how to configure the vm.* sysctl hierarchy, boot‑time parameters (transparent_hugepage, hugepagesz, default_hugepagesz), and eBPF‑specific knobs (bpf_jit_limit, bpf_map_max_entries) to achieve deterministic latency and maximal throughput.

Key Concepts

• Zone Watermarks – min, low, high control when kswapd/reclaim kicks in.
• Per‑CPU Page Cache (PCP) – Reduces lock contention on the buddy allocator; size tuned via vm.percpu_pagelist_fraction.
• Compaction & Migration – vm.compaction_proactiveness and vm.page_migration affect hugepage availability.
• Hugepage Reservation – Static (hugepages=) vs. dynamic (transparent_hugepage=always) pools.

All recommendations are validated on a dual‑socket Intel Xeon Platinum 8380 (2.3 GHz, 40 cores) running kernel 6.8 with BPF JIT enabled.