linux kernel-4.9 PageActive PageLRU等定义

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最新推荐文章于 2024-08-20 02:29:03 发布

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分类专栏： linux驱动

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本文详细介绍了Linux内核中页标志的管理宏，如PAGEFLAG、TESTPAGEFLAG、SETPAGEFLAG等，以及它们在页面状态如PG_locked、PG_dirty等中的应用。这些宏用于操作和检查页面的原子性标志，涉及页面的锁、更新、脏页、LRU列表等关键状态。此外，还讨论了页面字段的用途，包括区分内存域、NUMA节点和页状态。

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code path：https://elixir.bootlin.com/linux/v4.9.269/source/include/linux/page-flags.h

PAGEFLAG(Active, active, PF_HEAD)
 __CLEARPAGEFLAG(Active, active, PF_HEAD)
TESTCLEARFLAG(Active, active, PF_HEAD)

#define PAGEFLAG(uname, lname, policy)					\
	TESTPAGEFLAG(uname, lname, policy)				\
	SETPAGEFLAG(uname, lname, policy)				\
	CLEARPAGEFLAG(uname, lname, policy)
/*
 * Macros to create function definitions for page flags
 */
#define TESTPAGEFLAG(uname, lname, policy)				\
static __always_inline int Page##uname(struct page *page)		\
	{ return test_bit(PG_##lname, &policy(page, 0)->flags); }
#define SETPAGEFLAG(uname, lname, policy)				\
static __always_inline void SetPage##uname(struct page *page)		\
	{ set_bit(PG_##lname, &policy(page, 1)->flags); }

#define __CLEARPAGEFLAG(uname, lname, policy)				\
static __always_inline void __ClearPage##uname(struct page *page)	\
	{ __clear_bit(PG_##lname, &policy(page, 1)->flags); }

上述就分别定义了 PageActive 、SetPageActive、__ClearPageActive 函数

上述分别设置为page的

/*
 * Don't use the *_dontuse flags.  Use the macros.  Otherwise you'll break
 * locked- and dirty-page accounting.
 *
 * The page flags field is split into two parts, the main flags area
 * which extends from the low bits upwards, and the fields area which
 * extends from the high bits downwards.
 *
 *  | FIELD | ... | FLAGS |
 *  N-1           ^       0
 *               (NR_PAGEFLAGS)
 *
 * The fields area is reserved for fields mapping zone, node (for NUMA) and
 * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
 * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
 */
enum pageflags {
	PG_locked,		/* Page is locked. Don't touch. */
	PG_error,
	PG_referenced,
	PG_uptodate,
	PG_dirty,
	PG_lru,
	PG_active,
	PG_slab,
	PG_owner_priv_1,	/* Owner use. If pagecache, fs may use*/
	PG_arch_1,
	PG_reserved,
	PG_private,		/* If pagecache, has fs-private data */
	PG_private_2,		/* If pagecache, has fs aux data */
	PG_writeback,		/* Page is under writeback */
	PG_head,		/* A head page */
	PG_swapcache,		/* Swap page: swp_entry_t in private */
	PG_mappedtodisk,	/* Has blocks allocated on-disk */
	PG_reclaim,		/* To be reclaimed asap */
	PG_swapbacked,		/* Page is backed by RAM/swap */
	PG_unevictable,		/* Page is "unevictable"  */
#ifdef CONFIG_MMU
	PG_mlocked,		/* Page is vma mlocked */
#endif
#ifdef CONFIG_ARCH_USES_PG_UNCACHED
	PG_uncached,		/* Page has been mapped as uncached */
#endif
#ifdef CONFIG_MEMORY_FAILURE
	PG_hwpoison,		/* hardware poisoned page. Don't touch */
#endif
#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
	PG_young,
	PG_idle,
#endif
	__NR_PAGEFLAGS,

	/* Filesystems */
	PG_checked = PG_owner_priv_1,

	/* Two page bits are conscripted by FS-Cache to maintain local caching
	 * state.  These bits are set on pages belonging to the netfs's inodes
	 * when those inodes are being locally cached.
	 */
	PG_fscache = PG_private_2,	/* page backed by cache */

	/* XEN */
	/* Pinned in Xen as a read-only pagetable page. */
	PG_pinned = PG_owner_priv_1,
	/* Pinned as part of domain save (see xen_mm_pin_all()). */
	PG_savepinned = PG_dirty,
	/* Has a grant mapping of another (foreign) domain's page. */
	PG_foreign = PG_owner_priv_1,

	/* SLOB */
	PG_slob_free = PG_private,

	/* Compound pages. Stored in first tail page's flags */
	PG_double_map = PG_private_2,

	/* non-lru isolated movable page */
	PG_isolated = PG_reclaim,
};

struct page {
	/* First double word block */
	unsigned long flags;		/* Atomic flags, some possibly
}

flags 字段代表着如下四种含义：
section	主要用于稀疏内存模型SPARSEMEM
node	NUMA节点号, 标识该page属于哪一个节点
zone	内存域标志，标识该page属于哪一个zone
flag	page的状态标识

section	主要用于稀疏内存模型SPARSEMEM，可忽略
node	NUMA节点号, 标识该page属于哪一个节点
zone	内存域标志，标识该page属于哪一个zone
flag	page的状态标识