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*参照元 [#n88d602c] #backlinks *説明 [#j13b4430] -パス: [[linux-4.4.1/include/linux/mm_types.h]] -FIXME: これは何？ --説明 **参考 [#wa5fac1f] *実装 [#vb49edd3] /* * Each physical page in the system has a struct page associated with * it to keep track of whatever it is we are using the page for at the * moment. Note that we have no way to track which tasks are using * a page, though if it is a pagecache page, rmap structures can tell us * who is mapping it. * * The objects in struct page are organized in double word blocks in * order to allows us to use atomic double word operations on portions * of struct page. That is currently only used by slub but the arrangement * allows the use of atomic double word operations on the flags/mapping * and lru list pointers also. */ struct page { /* First double word block */ unsigned long flags; /* Atomic flags, some possibly * updated asynchronously */ union { struct address_space *mapping; /* If low bit clear, points to * inode address_space, or NULL. * If page mapped as anonymous * memory, low bit is set, and * it points to anon_vma object: * see PAGE_MAPPING_ANON below. */ void *s_mem; /* slab first object */ }; - --[[linux-4.4.1/address_space]] /* Second double word */ struct { union { pgoff_t index; /* Our offset within mapping. */ void *freelist; /* sl[aou]b first free object */ }; - --[[linux-4.4.1/pgoff_t]] union { #if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \ defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE) - --[[linux-4.4.1/CONFIG_HAVE_CMPXCHG_DOUBLE]] --[[linux-4.4.1/CONFIG_HAVE_ALIGNED_STRUCT_PAGE]] /* Used for cmpxchg_double in slub */ unsigned long counters; #else /* * Keep _count separate from slub cmpxchg_double data. * As the rest of the double word is protected by * slab_lock but _count is not. */ unsigned counters; #endif struct { union { /* * Count of ptes mapped in * mms, to show when page is * mapped & limit reverse map * searches. * * Used also for tail pages * refcounting instead of * _count. Tail pages cannot * be mapped and keeping the * tail page _count zero at * all times guarantees * get_page_unless_zero() will * never succeed on tail * pages. */ atomic_t _mapcount; - --[[linux-4.4.1/atomic_t]] struct { /* SLUB */ unsigned inuse:16; unsigned objects:15; unsigned frozen:1; }; int units; /* SLOB */ }; atomic_t _count; /* Usage count, see below. */ }; unsigned int active; /* SLAB */ }; }; /* * Third double word block * * WARNING: bit 0 of the first word encode PageTail(). That means * the rest users of the storage space MUST NOT use the bit to * avoid collision and false-positive PageTail(). */ union { struct list_head lru; /* Pageout list, eg. active_list * protected by zone->lru_lock ! * Can be used as a generic list * by the page owner. */ - --[[linux-4.4.1/list_head]] struct { /* slub per cpu partial pages */ struct page *next; /* Next partial slab */ #ifdef CONFIG_64BIT - --[[linux-4.4.1/CONFIG_64BIT]] int pages; /* Nr of partial slabs left */ int pobjects; /* Approximate # of objects */ #else short int pages; short int pobjects; #endif }; struct rcu_head rcu_head; /* Used by SLAB * when destroying via RCU */ - --[[linux-4.4.1/rcu_head]] /* Tail pages of compound page */ struct { unsigned long compound_head; /* If bit zero is set */ /* First tail page only */ #ifdef CONFIG_64BIT /* * On 64 bit system we have enough space in struct page * to encode compound_dtor and compound_order with * unsigned int. It can help compiler generate better or * smaller code on some archtectures. */ unsigned int compound_dtor; unsigned int compound_order; #else unsigned short int compound_dtor; unsigned short int compound_order; #endif }; #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS - --[[linux-4.4.1/CONFIG_TRANSPARENT_HUGEPAGE]] --[[linux-4.4.1/USE_SPLIT_PMD_PTLOCKS]] struct { unsigned long __pad; /* do not overlay pmd_huge_pte * with compound_head to avoid * possible bit 0 collision. */ pgtable_t pmd_huge_pte; /* protected by page->ptl */ }; - --[[linux-4.4.1/pgtable_t]] #endif }; /* Remainder is not double word aligned */ union { unsigned long private; /* Mapping-private opaque data: * usually used for buffer_heads * if PagePrivate set; used for * swp_entry_t if PageSwapCache; * indicates order in the buddy * system if PG_buddy is set. */ #if USE_SPLIT_PTE_PTLOCKS #if ALLOC_SPLIT_PTLOCKS - --[[linux-4.4.1/USE_SPLIT_PTE_PTLOCKS]] --[[linux-4.4.1/ALLOC_SPLIT_PTLOCKS]] spinlock_t *ptl; #else spinlock_t ptl; #endif - --[[linux-4.4.1/spinlock_t]] #endif struct kmem_cache *slab_cache; /* SL[AU]B: Pointer to slab */ }; - --[[linux-4.4.1/kmem_cache]] #ifdef CONFIG_MEMCG - --[[linux-4.4.1/CONFIG_MEMCG]] struct mem_cgroup *mem_cgroup; - --[[linux-4.4.1/mem_cgroup]] #endif /* * On machines where all RAM is mapped into kernel address space, * we can simply calculate the virtual address. On machines with * highmem some memory is mapped into kernel virtual memory * dynamically, so we need a place to store that address. * Note that this field could be 16 bits on x86 ... ;) * * Architectures with slow multiplication can define * WANT_PAGE_VIRTUAL in asm/page.h */ #if defined(WANT_PAGE_VIRTUAL) - --[[linux-4.4.1/WANT_PAGE_VIRTUAL]] void *virtual; /* Kernel virtual address (NULL if not kmapped, ie. highmem) */ #endif /* WANT_PAGE_VIRTUAL */ #ifdef CONFIG_KMEMCHECK - --[[linux-4.4.1/CONFIG_KMEMCHECK]] /* * kmemcheck wants to track the status of each byte in a page; this * is a pointer to such a status block. NULL if not tracked. */ void *shadow; #endif #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS - --[[linux-4.4.1/LAST_CPUPID_NOT_IN_PAGE_FLAGS]] int _last_cpupid; #endif } /* * The struct page can be forced to be double word aligned so that atomic ops * on double words work. The SLUB allocator can make use of such a feature. */ #ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE - --[[linux-4.4.1/CONFIG_HAVE_ALIGNED_STRUCT_PAGE]] __aligned(2 * sizeof(unsigned long)) - --[[linux-4.4.1/__aligned()]] #endif ; *コメント [#k45df037]
