Before:

struct page {
	long unsigned int          flags;                /*     0     8 */
	union {
		struct address_space * mapping;          /*           8 */
		void *             s_mem;                /*           8 */
		atomic_t           compound_mapcount;    /*           4 */
	};                                               /*     8     8 */
	union {
		long unsigned int  index;                /*           8 */
		void *             freelist;             /*           8 */
	};                                               /*    16     8 */
	union {
		long unsigned int  counters;             /*           8 */
		struct {
			union {
				atomic_t _mapcount;      /*           4 */
				unsigned int active;     /*           4 */
				struct {
					unsigned int inuse:16; /*    24:16  4 */
					unsigned int objects:15; /*    24: 1  4 */
					unsigned int frozen:1; /*    24: 0  4 */
				};                       /*           4 */
				int units;               /*           4 */
			};                               /*    24     4 */
			atomic_t   _refcount;            /*    28     4 */
		};                                       /*           8 */
	};                                               /*    24     8 */
	union {
		struct list_head   lru;                  /*          16 */
		struct dev_pagemap * pgmap;              /*           8 */
		struct {
			struct page * next;              /*    32     8 */
			int        pages;                /*    40     4 */
			int        pobjects;             /*    44     4 */
		};                                       /*          16 */
		struct callback_head callback_head;      /*          16 */
		struct {
			long unsigned int compound_head; /*    32     8 */
			unsigned int compound_dtor;      /*    40     4 */
			unsigned int compound_order;     /*    44     4 */
		};                                       /*          16 */
		struct {
			long unsigned int __pad;         /*    32     8 */
			pgtable_t  pmd_huge_pte;         /*    40     8 */
		};                                       /*          16 */
	};                                               /*    32    16 */
	union {
		long unsigned int  private;              /*           8 */
		spinlock_t         ptl;                  /*           4 */
		struct kmem_cache * slab_cache;          /*           8 */
	};                                               /*    48     8 */
	struct mem_cgroup *        mem_cgroup;           /*    56     8 */

	/* size: 64, cachelines: 1, members: 7 */
};

After:

struct page {
	long unsigned int          flags;                /*     0     8 */
	union {
		struct address_space * mapping;          /*     8     8 */
		void *             s_mem;                /*     8     8 */
		atomic_t           compound_mapcount;    /*     8     4 */
	};                                               /*     8     8 */
	union {
		long unsigned int  index;                /*    16     8 */
		void *             freelist;             /*    16     8 */
	};                                               /*    16     8 */
	union {
		long unsigned int  counters;             /*    24     8 */
		struct {
			union {
				atomic_t _mapcount;      /*    24     4 */
				unsigned int active;     /*    24     4 */
				struct {
					unsigned int inuse:16; /*    24:16  4 */
					unsigned int objects:15; /*    24: 1  4 */
					unsigned int frozen:1; /*    24: 0  4 */
				};                       /*    24     4 */
				int units;               /*    24     4 */
			};                               /*    24     4 */
			atomic_t   _refcount;            /*    28     4 */
		};                                       /*    24     8 */
	};                                               /*    24     8 */
	union {
		struct list_head   lru;                  /*    32    16 */
		struct dev_pagemap * pgmap;              /*    32     8 */
		struct {
			struct page * next;              /*    32     8 */
			int        pages;                /*    40     4 */
			int        pobjects;             /*    44     4 */
		};                                       /*    32    16 */
		struct callback_head callback_head;      /*    32    16 */
		struct {
			long unsigned int compound_head; /*    32     8 */
			unsigned int compound_dtor;      /*    40     4 */
			unsigned int compound_order;     /*    44     4 */
		};                                       /*    32    16 */
		struct {
			long unsigned int __pad;         /*    32     8 */
			pgtable_t  pmd_huge_pte;         /*    40     8 */
		};                                       /*    32    16 */
	};                                               /*    32    16 */
	union {
		long unsigned int  private;              /*    48     8 */
		spinlock_t         ptl;                  /*    48     4 */
		struct kmem_cache * slab_cache;          /*    48     8 */
	};                                               /*    48     8 */
	struct mem_cgroup *        mem_cgroup;           /*    56     8 */

	/* size: 64, cachelines: 1, members: 7 */
};

Diff:

--- /tmp/before	2017-12-18 22:27:25.637107705 -0300
+++ /tmp/after	2017-12-18 22:27:43.512080039 -0300
@@ -1,53 +1,53 @@
 struct page {
 	long unsigned int          flags;                /*     0     8 */
 	union {
-		struct address_space * mapping;          /*           8 */
-		void *             s_mem;                /*           8 */
-		atomic_t           compound_mapcount;    /*           4 */
+		struct address_space * mapping;          /*     8     8 */
+		void *             s_mem;                /*     8     8 */
+		atomic_t           compound_mapcount;    /*     8     4 */
 	};                                               /*     8     8 */
 	union {
-		long unsigned int  index;                /*           8 */
-		void *             freelist;             /*           8 */
+		long unsigned int  index;                /*    16     8 */
+		void *             freelist;             /*    16     8 */
 	};                                               /*    16     8 */
 	union {
-		long unsigned int  counters;             /*           8 */
+		long unsigned int  counters;             /*    24     8 */
 		struct {
 			union {
-				atomic_t _mapcount;      /*           4 */
-				unsigned int active;     /*           4 */
+				atomic_t _mapcount;      /*    24     4 */
+				unsigned int active;     /*    24     4 */
 				struct {
 					unsigned int inuse:16; /*    24:16  4 */
 					unsigned int objects:15; /*    24: 1  4 */
 					unsigned int frozen:1; /*    24: 0  4 */
-				};                       /*           4 */
-				int units;               /*           4 */
+				};                       /*    24     4 */
+				int units;               /*    24     4 */
 			};                               /*    24     4 */
 			atomic_t   _refcount;            /*    28     4 */
-		};                                       /*           8 */
+		};                                       /*    24     8 */
 	};                                               /*    24     8 */
 	union {
-		struct list_head   lru;                  /*          16 */
-		struct dev_pagemap * pgmap;              /*           8 */
+		struct list_head   lru;                  /*    32    16 */
+		struct dev_pagemap * pgmap;              /*    32     8 */
 		struct {
 			struct page * next;              /*    32     8 */
 			int        pages;                /*    40     4 */
 			int        pobjects;             /*    44     4 */
-		};                                       /*          16 */
-		struct callback_head callback_head;      /*          16 */
+		};                                       /*    32    16 */
+		struct callback_head callback_head;      /*    32    16 */
 		struct {
 			long unsigned int compound_head; /*    32     8 */
 			unsigned int compound_dtor;      /*    40     4 */
 			unsigned int compound_order;     /*    44     4 */
-		};                                       /*          16 */
+		};                                       /*    32    16 */
 		struct {
 			long unsigned int __pad;         /*    32     8 */
 			pgtable_t  pmd_huge_pte;         /*    40     8 */
-		};                                       /*          16 */
+		};                                       /*    32    16 */
 	};                                               /*    32    16 */
 	union {
-		long unsigned int  private;              /*           8 */
-		spinlock_t         ptl;                  /*           4 */
-		struct kmem_cache * slab_cache;          /*           8 */
+		long unsigned int  private;              /*    48     8 */
+		spinlock_t         ptl;                  /*    48     4 */
+		struct kmem_cache * slab_cache;          /*    48     8 */
 	};                                               /*    48     8 */
 	struct mem_cgroup *        mem_cgroup;           /*    56     8 */