This article explains the challenges of allocating large contiguous physical memory in Linux, introduces the Contiguous Memory Allocator (CMA) as a solution, and provides in‑depth coverage of its design, reservation, migration, data structures, initialization, configuration, usage in drivers, and debugging techniques.
This article explains OTA update mechanisms, analyzes why over‑the‑air upgrades cause frequent device reboots due to OOM‑killer and memory fragmentation, and provides concrete steps to disable panic_on_oom and adjust CMA settings to prevent crashes.
This comprehensive guide walks through Linux memory management, explaining CPU memory access, virtual‑to‑physical address translation, page‑table structures, zone organization, the buddy and slab allocators, vmalloc, page‑fault handling, and the Contiguous Memory Allocator (CMA) with detailed code examples and diagrams.
Linux’s Contiguous Memory Allocator (CMA) reserves and manages large physical memory blocks for devices by integrating with the Buddy system, using structures like struct cma, bitmap allocation, and APIs such as cma_init_reserved_mem and cma_alloc, while handling page migration, LRU and per‑CPU PCP caches to ensure efficient allocation and release.
