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Commit 61e06037 authored by Zachary Amsden's avatar Zachary Amsden Committed by Linus Torvalds
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[PATCH] x86_64: avoid some atomic operations during address space destruction 



Any architecture that has hardware updated A/D bits that require
synchronization against other processors during PTE operations can benefit
from doing non-atomic PTE updates during address space destruction.
Originally done on i386, now ported to x86_64.

Doing a read/write pair instead of an xchg() operation saves the implicit
lock, which turns out to be a big win on 32-bit (esp w PAE).

Signed-off-by: default avatarZachary Amsden <zach@vmware.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a600388d

include/asm-x86_64/pgtable.h

+14 −0
Original line number Diff line number Diff line
@@ -104,6 +104,19 @@ extern inline void pgd_clear (pgd_t * pgd) 
((unsigned long) __va(pud_val(pud) & PHYSICAL_PAGE_MASK))



#define ptep_get_and_clear(mm,addr,xp)	__pte(xchg(&(xp)->pte, 0))



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

{

	pte_t pte;

	if (full) {

		pte = *ptep;

		*ptep = __pte(0);

	} else {

		pte = ptep_get_and_clear(mm, addr, ptep);

	}

	return pte;

}



#define pte_same(a, b)		((a).pte == (b).pte)



#define PMD_SIZE	(1UL << PMD_SHIFT)
@@ -434,6 +447,7 @@ extern int kern_addr_valid(unsigned long addr); 
#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG

#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_DIRTY

#define __HAVE_ARCH_PTEP_GET_AND_CLEAR

#define __HAVE_ARCH_PTEP_GET_AND_CLEAR_FULL

#define __HAVE_ARCH_PTEP_SET_WRPROTECT

#define __HAVE_ARCH_PTE_SAME

#include <asm-generic/pgtable.h>