From: Matthew Wilcox <willy@infradead.org> To: linux-mm@kvack.org Cc: "Matthew Wilcox" <mawilcox@microsoft.com>, "Andrew Morton" <akpm@linux-foundation.org>, "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>, "Christoph Lameter" <cl@linux.com>, "Lai Jiangshan" <jiangshanlai@gmail.com>, "Pekka Enberg" <penberg@kernel.org>, "Vlastimil Babka" <vbabka@suse.cz>, "Dave Hansen" <dave.hansen@linux.intel.com>, "Jérôme Glisse" <jglisse@redhat.com> Subject: [PATCH v5 07/17] mm: Combine first three unions in struct page Date: Fri, 4 May 2018 11:33:08 -0700 [thread overview] Message-ID: <20180504183318.14415-8-willy@infradead.org> (raw) In-Reply-To: <20180504183318.14415-1-willy@infradead.org> From: Matthew Wilcox <mawilcox@microsoft.com> By combining these three one-word unions into one three-word union, we make it easier for users to add their own multi-word fields to struct page, as well as making it obvious that SLUB needs to keep its double-word alignment for its freelist & counters. No field moves position; verified with pahole. Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- include/linux/mm_types.h | 66 ++++++++++++++++++++-------------------- 1 file changed, 33 insertions(+), 33 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 9828cd170251..629a7b568ed7 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -70,46 +70,46 @@ struct hmm; #endif struct page { - /* First double word block */ unsigned long flags; /* Atomic flags, some possibly * updated asynchronously */ + /* Three words (12/24 bytes) are available in this union. */ union { - /* See page-flags.h for the definition of PAGE_MAPPING_FLAGS */ - struct address_space *mapping; - - struct kmem_cache *slab_cache; /* SL[AU]B: Pointer to slab */ + struct { /* Page cache and anonymous pages */ + /* 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 */ + 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; + }; + }; + }; atomic_t compound_mapcount; /* first tail page */ - /* page_deferred_list().next -- second tail page */ - }; - - /* Second double word */ - union { - pgoff_t index; /* Our offset within mapping. */ - void *freelist; /* sl[aou]b first free object */ - /* page_deferred_list().prev -- second tail page */ - }; - - union { - /* - * 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; -#if USE_SPLIT_PTE_PTLOCKS + struct list_head deferred_list; /* second tail page */ + struct { /* Page table pages */ + unsigned long _pt_pad_2; /* mapping */ + unsigned long _pt_pad_3; #if ALLOC_SPLIT_PTLOCKS - spinlock_t *ptl; + spinlock_t *ptl; #else - spinlock_t ptl; -#endif + spinlock_t ptl; #endif - void *s_mem; /* slab first object */ - unsigned long counters; /* SLUB */ - struct { /* SLUB */ - unsigned inuse:16; - unsigned objects:15; - unsigned frozen:1; }; }; -- 2.17.0
next prev parent reply other threads:[~2018-05-04 18:33 UTC|newest] Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-05-04 18:33 [PATCH v5 00/17] Rearrange " Matthew Wilcox 2018-05-04 18:33 ` [PATCH v5 01/17] s390: Use _refcount for pgtables Matthew Wilcox 2018-05-04 18:33 ` [PATCH v5 02/17] mm: Split page_type out from _mapcount Matthew Wilcox 2018-05-14 14:33 ` Vlastimil Babka 2018-05-04 18:33 ` [PATCH v5 03/17] mm: Mark pages in use for page tables Matthew Wilcox 2018-05-04 18:33 ` [PATCH v5 04/17] mm: Switch s_mem and slab_cache in struct page Matthew Wilcox 2018-05-07 14:58 ` Christopher Lameter 2018-05-14 14:37 ` Vlastimil Babka 2018-05-04 18:33 ` [PATCH v5 05/17] mm: Move 'private' union within " Matthew Wilcox 2018-05-04 18:33 ` [PATCH v5 06/17] mm: Move _refcount out of struct page union Matthew Wilcox 2018-05-04 18:33 ` Matthew Wilcox [this message] 2018-05-14 14:42 ` [PATCH v5 07/17] mm: Combine first three unions in struct page Vlastimil Babka 2018-05-04 18:33 ` [PATCH v5 08/17] mm: Use page->deferred_list Matthew Wilcox 2018-05-04 18:33 ` [PATCH v5 09/17] mm: Move lru union within struct page Matthew Wilcox 2018-05-04 18:33 ` [PATCH v5 10/17] mm: Combine LRU and main union in " Matthew Wilcox 2018-05-04 18:33 ` [PATCH v5 11/17] mm: Improve struct page documentation Matthew Wilcox 2018-05-15 9:22 ` Vlastimil Babka 2018-05-04 18:33 ` [PATCH v5 12/17] mm: Add pt_mm to struct page Matthew Wilcox 2018-05-15 9:27 ` Vlastimil Babka 2018-05-15 12:23 ` Matthew Wilcox 2018-05-04 18:33 ` [PATCH v5 13/17] mm: Add hmm_data " Matthew Wilcox 2018-05-15 9:32 ` Vlastimil Babka 2018-05-15 12:40 ` Vlastimil Babka 2018-05-04 18:33 ` [PATCH v5 14/17] slab,slub: Remove rcu_head size checks Matthew Wilcox 2018-05-15 11:30 ` Vlastimil Babka 2018-05-04 18:33 ` [PATCH v5 15/17] slub: Remove kmem_cache->reserved Matthew Wilcox 2018-05-04 18:33 ` [PATCH v5 16/17] slub: Remove 'reserved' file from sysfs Matthew Wilcox 2018-05-07 15:01 ` Christopher Lameter 2018-05-04 18:33 ` [PATCH v5 17/17] mm: Distinguish VMalloc pages Matthew Wilcox 2018-05-04 20:52 ` [PATCH v5 00/17] Rearrange struct page Andrew Morton 2018-05-04 21:25 ` Matthew Wilcox
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