Commit 25e4df5b authored Sep 30, 2006 by Zachary Amsden Committed by Linus Torvalds Oct 01, 2006

[PATCH] paravirt: combine flush accessed dirty.patch



Remove ptep_test_and_clear_{dirty|young} from i386, and instead use the
dominating functions, ptep_clear_flush_{dirty|young}.  This allows the TLB
page flush to be contained in the same macro, and allows for an eager
optimization - if reading the PTE initially returned dirty/accessed, we can
assume the fact that no subsequent update to the PTE which cleared accessed /
dirty has occurred, as the only way A/D bits can change without holding the
page table lock is if a remote processor clears them.  This eliminates an
extra branch which came from the generic version of the code, as we know that
no other CPU could have cleared the A/D bit, so the flush will always be
needed.

We still export these two defines, even though we do not actually define
the macros in the i386 code:

 #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
 #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_DIRTY

The reason for this is that the only use of these functions is within the
generic clear_flush functions, and we want a strong guarantee that there
are no other users of these functions, so we want to prevent the generic
code from defining them for us.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 6606c3e0

include/asm-i386/pgtable.h

+28 −13

Original line number	Diff line number	Diff line
		@@ -262,21 +262,36 @@ do { \
		} \
		} while (0)

		/*
		* We don't actually have these, but we want to advertise them so that
		* we can encompass the flush here.
		*/
		#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_DIRTY
		static inline int ptep_test_and_clear_dirty(struct vm_area_struct vma, unsigned long addr, pte_t ptep)
		{
		if (!pte_dirty(*ptep))
		return 0;
		return test_and_clear_bit(_PAGE_BIT_DIRTY, &ptep->pte_low);
		}

		#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
		static inline int ptep_test_and_clear_young(struct vm_area_struct vma, unsigned long addr, pte_t ptep)
		{
		if (!pte_young(*ptep))
		return 0;
		return test_and_clear_bit(_PAGE_BIT_ACCESSED, &ptep->pte_low);
		}

		#define __HAVE_ARCH_PTEP_CLEAR_DIRTY_FLUSH
		#define ptep_clear_flush_dirty(vma, address, ptep) \
		({ \
		int __dirty; \
		__dirty = pte_dirty(*(ptep)); \
		if (__dirty) { \
		clear_bit(_PAGE_BIT_DIRTY, &(ptep)->pte_low); \
		flush_tlb_page(vma, address); \
		} \
		__dirty; \
		})

		#define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
		#define ptep_clear_flush_young(vma, address, ptep) \
		({ \
		int __young; \
		__young = pte_young(*(ptep)); \
		if (__young) { \
		clear_bit(_PAGE_BIT_ACCESSED, &(ptep)->pte_low); \
		flush_tlb_page(vma, address); \
		} \
		__young; \
		})

		#define __HAVE_ARCH_PTEP_GET_AND_CLEAR_FULL
		static inline pte_t ptep_get_and_clear_full(struct mm_struct mm, unsigned long addr, pte_t ptep, int full)