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Commit 597d795a authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
Browse files

mm: do not allocate page->ptl dynamically, if spinlock_t fits to long 



In struct page we have enough space to fit long-size page->ptl there,
but we use dynamically-allocated page->ptl if size(spinlock_t) is larger
than sizeof(int).

It hurts 64-bit architectures with CONFIG_GENERIC_LOCKBREAK, where
sizeof(spinlock_t) == 8, but it easily fits into struct page.

Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: default avatarHugh Dickins <hughd@google.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fff4068c

include/linux/lockref.h

+1 −1
Original line number Diff line number Diff line
@@ -19,7 +19,7 @@ 


#define USE_CMPXCHG_LOCKREF \

	(IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \

	 IS_ENABLED(CONFIG_SMP) && !BLOATED_SPINLOCKS)

	 IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)



struct lockref {

	union {

include/linux/mm.h

+3 −3
Original line number Diff line number Diff line
@@ -1317,7 +1317,7 @@ static inline pmd_t *pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long a 
#endif /* CONFIG_MMU && !__ARCH_HAS_4LEVEL_HACK */



#if USE_SPLIT_PTE_PTLOCKS

#if BLOATED_SPINLOCKS

#if ALLOC_SPLIT_PTLOCKS

extern bool ptlock_alloc(struct page *page);

extern void ptlock_free(struct page *page);
@@ -1325,7 +1325,7 @@ static inline spinlock_t *ptlock_ptr(struct page *page) 
{

	return page->ptl;

}

#else /* BLOATED_SPINLOCKS */

#else /* ALLOC_SPLIT_PTLOCKS */

static inline bool ptlock_alloc(struct page *page)

{

	return true;
@@ -1339,7 +1339,7 @@ static inline spinlock_t *ptlock_ptr(struct page *page) 
{

	return &page->ptl;

}

#endif /* BLOATED_SPINLOCKS */

#endif /* ALLOC_SPLIT_PTLOCKS */



static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)

{

include/linux/mm_types.h

+2 −1
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ struct address_space; 
#define USE_SPLIT_PTE_PTLOCKS	(NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS)

#define USE_SPLIT_PMD_PTLOCKS	(USE_SPLIT_PTE_PTLOCKS && \

		IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))

#define ALLOC_SPLIT_PTLOCKS	(SPINLOCK_SIZE > BITS_PER_LONG/8)



/*

 * Each physical page in the system has a struct page associated with
@@ -155,7 +156,7 @@ struct page { 
						 * system if PG_buddy is set.

						 */

#if USE_SPLIT_PTE_PTLOCKS

#if BLOATED_SPINLOCKS

#if ALLOC_SPLIT_PTLOCKS

		spinlock_t *ptl;

#else

		spinlock_t ptl;

kernel/bounds.c

+1 −1
Original line number Diff line number Diff line
@@ -22,6 +22,6 @@ void foo(void) 
#ifdef CONFIG_SMP

	DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));

#endif

	DEFINE(BLOATED_SPINLOCKS, sizeof(spinlock_t) > sizeof(int));

	DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));

	/* End of constants */

}

mm/memory.c

+1 −1
Original line number Diff line number Diff line
@@ -4271,7 +4271,7 @@ void copy_user_huge_page(struct page *dst, struct page *src, 
}

#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */



#if USE_SPLIT_PTE_PTLOCKS && BLOATED_SPINLOCKS

#if ALLOC_SPLIT_PTLOCKS

bool ptlock_alloc(struct page *page)

{

	spinlock_t *ptl;