完善了README.md...

study/kernel/02-memory/01-description/01-memory/1.c

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+/*
+ * The pg_data_t structure is used in machines with CONFIG_DISCONTIGMEM
+ * (mostly NUMA machines?) to denote a higher-level memory zone than the
+ * zone denotes.
+ *
+ * On NUMA machines, each NUMA node would have a pg_data_t to describe
+ * it's memory layout.
+ *
+ * Memory statistics and page replacement data structures are maintained on a
+ * per-zone basis.
+ */
+struct bootmem_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_max_order;
+        enum zone_type classzone_idx;
+#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
+
+#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;
+#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
+} pg_data_t;