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 struct page 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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