Linux内存管理 | 五、物理内存空间布局及管理 #

/*
 * On NUMA machines, each NUMA node would have a pg_data_t to describe
 * it's memory layout. On UMA machines there is a single pglist_data which
 * describes the whole memory.
 *
 * Memory statistics and page replacement data structures are maintained on a
 * per-zone basis.
 */
typedef struct pglist_data {
    ...
    int node_id;
    struct page *node_mem_map;
    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 */
        
    ...    
} pg_data_t;

enum zone_type {
#ifdef CONFIG_ZONE_DMA
    ZONE_DMA,
#endif
#ifdef CONFIG_ZONE_DMA32
    ZONE_DMA32,
#endif
    ZONE_NORMAL,
#ifdef CONFIG_HIGHMEM
    ZONE_HIGHMEM,
#endif
    ZONE_MOVABLE,
#ifdef CONFIG_ZONE_DEVICE
    ZONE_DEVICE,
#endif
    __MAX_NR_ZONES
};

struct zone {
......
    struct pglist_data	*zone_pgdat;
    struct per_cpu_pageset __percpu *pageset;
 
 
    unsigned long		zone_start_pfn;
 
 
    /*
     * spanned_pages is the total pages spanned by the zone, including
     * holes, which is calculated as:
     * 	spanned_pages = zone_end_pfn - zone_start_pfn;
     *
     * present_pages is physical pages existing within the zone, which
     * is calculated as:
     *	present_pages = spanned_pages - absent_pages(pages in holes);
     *
     * managed_pages is present pages managed by the buddy system, which
     * is calculated as (reserved_pages includes pages allocated by the
     * bootmem allocator):
     *	managed_pages = present_pages - reserved_pages;
     *
     */
    unsigned long		managed_pages;
    unsigned long		spanned_pages;
    unsigned long		present_pages;
 
 
    const char		*name;
......
    /* free areas of different sizes */
    struct free_area	free_area[MAX_ORDER];
 
 
    /* zone flags, see below */
    unsigned long		flags;
 
 
    /* Primarily protects free_area */
    spinlock_t		lock;
......
} ____cacheline_internodealigned_in_

struct page {
    unsigned long flags;		/* Atomic flags, some possibly
                     * updated asynchronously */
union {
        struct {	/* Page cache and anonymous pages */
            /**
             * @lru: Pageout list, eg. active_list protected by
             * zone_lru_lock.  Sometimes used as a generic list
             * by the page owner.
             */
            struct list_head lru;
            /* See page-flags.h for PAGE_MAPPING_FLAGS */
            struct address_space *mapping;
            pgoff_t index;		/* Our offset within mapping. */
            /**
             * @private: Mapping-private opaque data.
             * Usually used for buffer_heads if PagePrivate.
             * Used for swp_entry_t if PageSwapCache.
             * Indicates order in the buddy system if PageBuddy.
             */
            unsigned long private;
        };
    
        struct {	/* slab, slob and slub */
                    union {
                        struct list_head slab_list;	/* uses lru */
                        struct {	/* Partial pages */
                            struct page *next;
        #ifdef CONFIG_64BIT
                            int pages;	/* Nr of pages left */
                            int pobjects;	/* Approximate count */
        #else
                            short int pages;
                            short int pobjects;
        #endif
                        };
            };
            
        struct kmem_cache *slab_cache; /* not slob */
                    /* Double-word boundary */
                    void *freelist;		/* first free object */
                    union {
                        void *s_mem;	/* slab: first object */
                        unsigned long counters;		/* SLUB */
                        struct {			/* SLUB */
                            unsigned inuse:16;
                            unsigned objects:15;
                            unsigned frozen:1;
                        };
                    };
                };
        .....
}