page fault scalability patch V10: [5/7] i386 atomic pte operations

[Christoph Lameter]

Changelog
	* Atomic pte operations for i386

Signed-off-by: Christoph Lameter <clameter@xxxxxxx>

Index: linux-2.6.9-rc4/include/asm-i386/pgtable.h
===================================================================
--- linux-2.6.9-rc4.orig/include/asm-i386/pgtable.h	2004-10-10 19:58:24.000000000 -0700
+++ linux-2.6.9-rc4/include/asm-i386/pgtable.h	2004-10-14 11:32:37.000000000 -0700
@@ -412,6 +412,7 @@
 #define __HAVE_ARCH_PTEP_SET_WRPROTECT
 #define __HAVE_ARCH_PTEP_MKDIRTY
 #define __HAVE_ARCH_PTE_SAME
+#define __HAVE_ARCH_ATOMIC_TABLE_OPS
 #include <asm-generic/pgtable.h>

 #endif /* _I386_PGTABLE_H */
Index: linux-2.6.9-rc4/include/asm-i386/pgtable-3level.h
===================================================================
--- linux-2.6.9-rc4.orig/include/asm-i386/pgtable-3level.h	2004-10-10 19:58:41.000000000 -0700
+++ linux-2.6.9-rc4/include/asm-i386/pgtable-3level.h	2004-10-14 11:32:37.000000000 -0700
@@ -6,7 +6,8 @@
  * tables on PPro+ CPUs.
  *
  * Copyright (C) 1999 Ingo Molnar <mingo@xxxxxxxxxx>
- */
+ * August 26, 2004 added ptep_cmpxchg and ptep_xchg <christoph@xxxxxxxxxxx>
+*/

 #define pte_ERROR(e) \
 	printk("%s:%d: bad pte %p(%08lx%08lx).\n", __FILE__, __LINE__, &(e), (e).pte_high, (e).pte_low)
@@ -141,4 +142,26 @@
 #define __pte_to_swp_entry(pte)		((swp_entry_t){ (pte).pte_high })
 #define __swp_entry_to_pte(x)		((pte_t){ 0, (x).val })

+/* Atomic PTE operations */
+static inline pte_t ptep_xchg(struct mm_struct *mm, pte_t *ptep, pte_t newval)
+{
+	pte_t res;
+
+	/* xchg acts as a barrier before the setting of the high bits.
+	 * (But we also have a cmpxchg8b. Why not use that? (cl))
+	  */
+	res.pte_low = xchg(&ptep->pte_low, newval.pte_low);
+	res.pte_high = ptep->pte_high;
+	ptep->pte_high = newval.pte_high;
+
+	return res;
+}
+
+
+static inline int ptep_cmpxchg(struct mm_struct *mm, unsigned long address, pte_t *ptep, pte_t oldval, pte_t newval)
+{
+	return cmpxchg(ptep, pte_val(oldval), pte_val(newval)) == pte_val(oldval);
+}
+
+
 #endif /* _I386_PGTABLE_3LEVEL_H */
Index: linux-2.6.9-rc4/include/asm-i386/pgtable-2level.h
===================================================================
--- linux-2.6.9-rc4.orig/include/asm-i386/pgtable-2level.h	2004-10-10 19:58:05.000000000 -0700
+++ linux-2.6.9-rc4/include/asm-i386/pgtable-2level.h	2004-10-14 11:32:37.000000000 -0700
@@ -82,4 +82,8 @@
 #define __pte_to_swp_entry(pte)		((swp_entry_t) { (pte).pte_low })
 #define __swp_entry_to_pte(x)		((pte_t) { (x).val })

+/* Atomic PTE operations */
+#define ptep_xchg(mm,xp,a)       __pte(xchg(&(xp)->pte_low, (a).pte_low))
+#define ptep_cmpxchg(mm,a,xp,oldpte,newpte) (cmpxchg(&(xp)->pte_low, (oldpte).pte_low, (newpte).pte_low)==(oldpte).pte_low)
+
 #endif /* _I386_PGTABLE_2LEVEL_H */
Index: linux-2.6.9-rc4/include/asm-i386/pgalloc.h
===================================================================
--- linux-2.6.9-rc4.orig/include/asm-i386/pgalloc.h	2004-10-10 19:57:02.000000000 -0700
+++ linux-2.6.9-rc4/include/asm-i386/pgalloc.h	2004-10-14 11:32:37.000000000 -0700
@@ -7,6 +7,8 @@
 #include <linux/threads.h>
 #include <linux/mm.h>		/* for struct page */

+#define PMD_NONE 0L
+
 #define pmd_populate_kernel(mm, pmd, pte) \
 		set_pmd(pmd, __pmd(_PAGE_TABLE + __pa(pte)))

@@ -16,6 +18,19 @@
 		((unsigned long long)page_to_pfn(pte) <<
 			(unsigned long long) PAGE_SHIFT)));
 }
+
+/* Atomic version */
+static inline int pmd_test_and_populate(struct mm_struct *mm, pmd_t *pmd, struct page *pte)
+{
+#ifdef CONFIG_X86_PAE
+	return cmpxchg8b( ((unsigned long long *)pmd), PMD_NONE, _PAGE_TABLE +
+		((unsigned long long)page_to_pfn(pte) <<
+			(unsigned long long) PAGE_SHIFT) ) == PMD_NONE;
+#else
+	return cmpxchg( (unsigned long *)pmd, PMD_NONE, _PAGE_TABLE + (page_to_pfn(pte) << PAGE_SHIFT)) == PMD_NONE;
+#endif
+}
+
 /*
  * Allocate and free page tables.
  */
@@ -49,6 +64,7 @@
 #define pmd_free(x)			do { } while (0)
 #define __pmd_free_tlb(tlb,x)		do { } while (0)
 #define pgd_populate(mm, pmd, pte)	BUG()
+#define pgd_test_and_populate(mm, pmd, pte)	({ BUG(); 1; })

 #define check_pgt_cache()	do { } while (0)

-
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