A.1＃【内存管理】——1.1.1 node:struct pglist_data

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_order;
    enum zone_type kswapd_classzone_idx;

    int kswapd_failures;        /* Number of 'reclaimed == 0' runs */

#ifdef CONFIG_COMPACTION
    int kcompactd_max_order;
    enum zone_type kcompactd_classzone_idx;
    wait_queue_head_t kcompactd_wait;
    struct task_struct *kcompactd;
#endif
#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
    /*
     * This is a per-node reserve of pages that are not available
     * to userspace allocations.
     */
    unsigned long        totalreserve_pages;

#ifdef CONFIG_NUMA
    /*
     * zone reclaim becomes active if more unmapped pages exist.
     */
    unsigned long        min_unmapped_pages;
    unsigned long        min_slab_pages;
#endif /* CONFIG_NUMA */

    /* Write-intensive fields used by page reclaim */
    ZONE_PADDING(_pad1_)
    spinlock_t        lru_lock;

#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 */

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
    spinlock_t split_queue_lock;
    struct list_head split_queue;
    unsigned long split_queue_len;
#endif

    /* Fields commonly accessed by the page reclaim scanner */
    struct lruvec        lruvec;

    /*
     * The target ratio of ACTIVE_ANON to INACTIVE_ANON pages on
     * this node's LRU.  Maintained by the pageout code.
     */
    unsigned int inactive_ratio;

    unsigned long        flags;

    ZONE_PADDING(_pad2_)

    /* Per-node vmstats */
    struct per_cpu_nodestat __percpu  *per_cpu_nodestats;
    atomic_long_t        vm_stat[NR_VM_NODE_STAT_ITEMS];
} pg_data_t;

 

node_zones[MAX_NR_ZONES]	对应该node包含的各个类型的zone
node_zonelists	该node的备选节点及内存域列表，见下一章讲解
node_mem_map	linux为每个物理页分配了一个struct page的管理结构体，并形成了一个结构体数组，node_mem_map即为数组的指针；pfn_to_page和page_to_pfn都借助该数组实现。
nr_zones	包含zone的个数
node_start_pfn	该node中内存的起始页帧号
node_present_pages	该node地址范围内的实际管理的页面数量
node_spanned_pages	该node地址范围内的所有page页数，包括空洞；目前还不清楚什么情况导致与node_present_pages不同。
node_id	节点标识符
kswapd	负责回收该node内存的内核线程，每个node对应一个内核线程kswapd
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
lru_lock	用于对LRU链表并行访问时进行保护
lruvec	LRU链表的集合
flags	内存域的当前状态, 在mmzone.h定义了zone的所有可用zone_flag
vm_stat	node的计数
ZONE_PADDING宏	作用是让前后的成员分布在不同的cache line中, 以空间换取时间。