sparc64: optimize struct page zeroing

[sfrench/cifs-2.6.git] / arch / sparc / include / asm / pgtable_64.h

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index fd9d9bac7cfa7b3ac96b1fa54dfba71f96e60916..5a9e96be16652bc13bb4e6cd0f298b0e613d5883 100644 (file)
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -231,6 +231,36 @@ extern unsigned long _PAGE_ALL_SZ_BITS;
 extern struct page *mem_map_zero;
 #define ZERO_PAGE(vaddr)       (mem_map_zero)
 
+/* This macro must be updated when the size of struct page grows above 80
+ * or reduces below 64.
+ * The idea that compiler optimizes out switch() statement, and only
+ * leaves clrx instructions
+ */
+#define        mm_zero_struct_page(pp) do {                                    \
+       unsigned long *_pp = (void *)(pp);                              \
+                                                                       \
+        /* Check that struct page is either 64, 72, or 80 bytes */     \
+       BUILD_BUG_ON(sizeof(struct page) & 7);                          \
+       BUILD_BUG_ON(sizeof(struct page) < 64);                         \
+       BUILD_BUG_ON(sizeof(struct page) > 80);                         \
+                                                                       \
+       switch (sizeof(struct page)) {                                  \
+       case 80:                                                        \
+               _pp[9] = 0;     /* fallthrough */                       \
+       case 72:                                                        \
+               _pp[8] = 0;     /* fallthrough */                       \
+       default:                                                        \
+               _pp[7] = 0;                                             \
+               _pp[6] = 0;                                             \
+               _pp[5] = 0;                                             \
+               _pp[4] = 0;                                             \
+               _pp[3] = 0;                                             \
+               _pp[2] = 0;                                             \
+               _pp[1] = 0;                                             \
+               _pp[0] = 0;                                             \
+       }                                                               \
+} while (0)
+
 /* PFNs are real physical page numbers.  However, mem_map only begins to record
  * per-page information starting at pfn_base.  This is to handle systems where
  * the first physical page in the machine is at some huge physical address,