memblocks_present

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已于 2022-02-23 08:54:16 修改 · 572 阅读

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#memblock

于 2022-02-14 14:46:18 首次发布

本文详细解析了Linux kernel 5.10中arm64架构下，如何使用memblocks_present和memory_present函数初始化内存区域。这两个函数主要负责将系统的内存标记为可用，并按照section进行划分，创建并标记mem_section结构体。在这个过程中，涉及到sparse内存模型的数据结构，包括memblock、mem_section、section_to_node_table等，以及section的分配、状态设置等步骤。文章深入探讨了Sparse内存模型的组织和管理机制。

memblocks_present

/*
 * Mark all memblocks as present using memory_present().
 * This is a convenience function that is useful to mark all of the systems                                                                                     
 * memory as present during initialization.                                                                                                                     
 */
static void __init memblocks_present(void)                                                                                                                      
{
   
          
        unsigned long start, end;                                                                                                                               
        int i, nid;                                                                                                                                             
        
        for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid)                                                                                             
                memory_present(nid, start, end);                                                                                                                
}

根据对for_each_mem_pfn_range的分析，memblocks_present实际就是遍历memblock.memory下的所有memblock_region区域，将每个memblock_region区域按section划分，创建对应的mem_section结构体，且通过mem_section的section_mem_map标记为在线状态

memory_present

/* Record a memory area against a node. */
static void __init memory_present(int nid, unsigned long start, unsigned long end)
{
   
   
        unsigned long pfn;

#ifdef CONFIG_SPARSEMEM_EXTREME
        if (unlikely(!mem_section)) {
   
   
                unsigned long size, align;

                size = sizeof(struct mem_section*) * NR_SECTION_ROOTS;
                align = 1 << (INTERNODE_CACHE_SHIFT);
                mem_section = memblock_alloc(size, align);
                if (!mem_section)
                        panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
                              __func__