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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 v6 05/17] mm: Move 'private' union within struct page
Date: Fri, 18 May 2018 12:45:07 -0700
Message-ID: <20180518194519.3820-6-willy@infradead.org> (raw)
In-Reply-To: <20180518194519.3820-1-willy@infradead.org>

From: Matthew Wilcox <mawilcox@microsoft.com>

By moving page->private to the fourth word of struct page, we can put
the SLUB counters in the same word as SLAB's s_mem and still do the
cmpxchg_double trick.  Now the SLUB counters no longer overlap with the
mapcount or refcount so we can drop the call to page_mapcount_reset()
and simplify set_page_slub_counters() to a single line.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 include/linux/mm_types.h | 56 ++++++++++++++++++----------------------
 mm/slub.c                | 20 ++------------
 2 files changed, 27 insertions(+), 49 deletions(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index e97a310a6abe..23378a789af4 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -65,15 +65,9 @@ struct hmm;
  */
 #ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE
 #define _struct_page_alignment	__aligned(2 * sizeof(unsigned long))
-#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE)
-#define _slub_counter_t		unsigned long
 #else
-#define _slub_counter_t		unsigned int
-#endif
-#else /* !CONFIG_HAVE_ALIGNED_STRUCT_PAGE */
 #define _struct_page_alignment
-#define _slub_counter_t		unsigned int
-#endif /* !CONFIG_HAVE_ALIGNED_STRUCT_PAGE */
+#endif
 
 struct page {
 	/* First double word block */
@@ -95,6 +89,30 @@ struct page {
 		/* 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
+#if ALLOC_SPLIT_PTLOCKS
+		spinlock_t *ptl;
+#else
+		spinlock_t ptl;
+#endif
+#endif
+		void *s_mem;			/* slab first object */
+		unsigned long counters;		/* SLUB */
+		struct {			/* SLUB */
+			unsigned inuse:16;
+			unsigned objects:15;
+			unsigned frozen:1;
+		};
+	};
+
 	union {
 		/*
 		 * If the page is neither PageSlab nor mappable to userspace,
@@ -104,13 +122,7 @@ struct page {
 		 */
 		unsigned int page_type;
 
-		_slub_counter_t counters;
 		unsigned int active;		/* SLAB */
-		struct {			/* SLUB */
-			unsigned inuse:16;
-			unsigned objects:15;
-			unsigned frozen:1;
-		};
 		int units;			/* SLOB */
 
 		struct {			/* Page cache */
@@ -179,24 +191,6 @@ struct page {
 #endif
 	};
 
-	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
-#if ALLOC_SPLIT_PTLOCKS
-		spinlock_t *ptl;
-#else
-		spinlock_t ptl;
-#endif
-#endif
-		void *s_mem;			/* slab first object */
-	};
-
 #ifdef CONFIG_MEMCG
 	struct mem_cgroup *mem_cgroup;
 #endif
diff --git a/mm/slub.c b/mm/slub.c
index 7fc13c46e975..05ca612a5fe6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -356,21 +356,6 @@ static __always_inline void slab_unlock(struct page *page)
 	__bit_spin_unlock(PG_locked, &page->flags);
 }
 
-static inline void set_page_slub_counters(struct page *page, unsigned long counters_new)
-{
-	struct page tmp;
-	tmp.counters = counters_new;
-	/*
-	 * page->counters can cover frozen/inuse/objects as well
-	 * as page->_refcount.  If we assign to ->counters directly
-	 * we run the risk of losing updates to page->_refcount, so
-	 * be careful and only assign to the fields we need.
-	 */
-	page->frozen  = tmp.frozen;
-	page->inuse   = tmp.inuse;
-	page->objects = tmp.objects;
-}
-
 /* Interrupts must be disabled (for the fallback code to work right) */
 static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
 		void *freelist_old, unsigned long counters_old,
@@ -392,7 +377,7 @@ static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page
 		if (page->freelist == freelist_old &&
 					page->counters == counters_old) {
 			page->freelist = freelist_new;
-			set_page_slub_counters(page, counters_new);
+			page->counters = counters_new;
 			slab_unlock(page);
 			return true;
 		}
@@ -431,7 +416,7 @@ static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
 		if (page->freelist == freelist_old &&
 					page->counters == counters_old) {
 			page->freelist = freelist_new;
-			set_page_slub_counters(page, counters_new);
+			page->counters = counters_new;
 			slab_unlock(page);
 			local_irq_restore(flags);
 			return true;
@@ -1689,7 +1674,6 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
 	__ClearPageSlabPfmemalloc(page);
 	__ClearPageSlab(page);
 
-	page_mapcount_reset(page);
 	page->mapping = NULL;
 	if (current->reclaim_state)
 		current->reclaim_state->reclaimed_slab += pages;
-- 
2.17.0

  parent reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-18 19:45 [PATCH v6 00/17] Rearrange " Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 01/17] s390: Use _refcount for pgtables Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 02/17] mm: Split page_type out from _mapcount Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 03/17] mm: Mark pages in use for page tables Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 04/17] mm: Switch s_mem and slab_cache in struct page Matthew Wilcox
2018-05-18 19:45 ` Matthew Wilcox [this message]
2018-05-18 19:45 ` [PATCH v6 06/17] mm: Move _refcount out of struct page union Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 07/17] mm: Combine first three unions in struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 08/17] mm: Use page->deferred_list Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 09/17] mm: Move lru union within struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 10/17] mm: Combine LRU and main union in " Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 11/17] mm: Improve struct page documentation Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 12/17] mm: Add pt_mm to struct page Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 13/17] mm: Add hmm_data " Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 14/17] slab,slub: Remove rcu_head size checks Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 15/17] slub: Remove kmem_cache->reserved Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 16/17] slub: Remove 'reserved' file from sysfs Matthew Wilcox
2018-05-18 19:45 ` [PATCH v6 17/17] mm: Distinguish VMalloc pages Matthew Wilcox
2018-05-22 16:10   ` Andrey Ryabinin
2018-05-22 17:58     ` Matthew Wilcox
2018-05-22 19:49       ` Andrew Morton
2018-05-22 19:57       ` Andrey Ryabinin
2018-05-22 20:19         ` Matthew Wilcox
2018-05-22 20:48           ` Andrew Morton
2018-05-22 21:45             ` Matthew Wilcox
2018-05-22 23:02               ` Andrew Morton
2018-05-23  6:36           ` Michal Hocko
2018-05-23  6:34         ` Michal Hocko
2018-05-23  9:14           ` Andrey Ryabinin
2018-05-23  9:25             ` Michal Hocko
2018-05-23  9:28               ` Andrey Ryabinin
2018-05-23  9:52                 ` Michal Hocko

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