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

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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: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2013-12-20 13:35:58 +02:00 • committed by Linus Torvalds
parent fff4068cba
commit 597d795a2a
5 changed files with 8 additions and 7 deletions
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2
include/linux/lockref.h
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@ -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 {