承接内存管理相关概念讲解相关数据结构。主要有
- pg_data_t: 表示节点；
- zone： 内存域；
- page: 页帧；
pglist_data定义如下：
<code>typedef struct pglist_data {
struct zone node_zones[MAX_NR_ZONES];
struct zonelist node_zonelists[MAX_ZONELISTS];
int nr_zones;
#ifdef CONFIG_FLAT_NODE_MEM_MAP /* means !SPARSEMEM */
struct page *node_mem_map;
#ifdef CONFIG_PAGE_EXTENSION
struct page_ext *node_page_ext;
#endif
#endif
#ifndef CONFIG_NO_BOOTMEM
struct bootmem_data *bdata;
#endif
#ifdef CONFIG_MEMORY_HOTPLUG
/*
* Must be held any time you expect node_start_pfn, node_present_pages
* or node_spanned_pages stay constant. Holding this will also
* guarantee that any pfn_valid() stays that way.
*
* pgdat_resize_lock() and pgdat_resize_unlock() are provided to
* manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG.
*
* Nests above zone->lock and zone->span_seqlock
*/
spinlock_t node_size_lock;
#endif
unsigned long node_start_pfn;
unsigned long node_present_pages; /* total number of physical pages */
unsigned long node_spanned_pages; /* total size of physical page
range, including holes */
int node_id;
wait_queue_head_t kswapd_wait;
wait_queue_head_t pfmemalloc_wait;
struct task_struct *kswapd; /* Protected by
mem_hotplug_begin/end() */
int kswapd_max_order;
enum zone_type classzone_idx;
#ifdef CONFIG_NUMA_BALANCING
/* Lock serializing the migrate rate limiting window */
spinlock_t numabalancing_migrate_lock;
/* Rate limiting time interval */
unsigned long numabalancing_migrate_next_window;
/* Number of pages migrated during the rate limiting time interval */
unsigned long numabalancing_migrate_nr_pages;
#endif
#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
/*
* If memory initialisation on large machines is deferred then this
* is the first PFN that needs to be initialised.
*/
unsigned long first_deferred_pfn;
/* Number of non-deferred pages */
unsigned long static_init_pgcnt;
#endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
} pg_data_t;
/<code>- node_zones是一个数组，包含节点中各内存域(ZONE_DMA, ZONE_DMA32, ZONE_NORMAL...)的数据结构;
- node_zonelists指定了节点的备用列表；
- nr_zones 指示了节点中不同内存域数目；
- node_mem_map描述节点的所有物理内存页面。包含节点的所有内存域；
- bdata 系统启动自举内存分配器数据结构实例；
- node_start_pfn 当前NUMA节点第一页帧逻辑编号。在UMA总是0.
- node_present_pages节点中页帧的数目；
- node_spanned_pages节点以页帧为单位计算的数目。由于空洞的存在可能不等于node_present_pages，应该是大于等于node_present_pages；
- node_id是全局节点ID；
- kswapd_wait：node的等待队列，交换守护列队进程的等待列表
- kswapd_max_order：需要释放的区域的长度，以页阶为单位
若系统节点多余一个，则内核会维护一个位图用于提供每个节点的状态信息，状态信息为一个enum。定义如下:
<code>enum node_states {
N_POSSIBLE, /* The node could become online at some point */
N_ONLINE, /* The node is online */
N_NORMAL_MEMORY, /* The node has regular memory */
#ifdef CONFIG_HIGHMEM
N_HIGH_MEMORY, /* The node has regular or high memory */
#else
N_HIGH_MEMORY = N_NORMAL_MEMORY,
#endif
#ifdef CONFIG_MOVABLE_NODE
N_MEMORY, /* The node has memory(regular, high, movable) */
#else
N_MEMORY = N_HIGH_MEMORY,
#endif
N_CPU, /* The node has one or more cpus */
NR_NODE_STATES
};/<code>
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