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: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/lockref.h b/include/linux/lockref.h
index c8929c3..4bfde0e 100644
--- a/include/linux/lockref.h
+++ b/include/linux/lockref.h
@@ -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 {
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1cedd00..3552717 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1317,7 +1317,7 @@
#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 @@
{
return page->ptl;
}
-#else /* BLOATED_SPINLOCKS */
+#else /* ALLOC_SPLIT_PTLOCKS */
static inline bool ptlock_alloc(struct page *page)
{
return true;
@@ -1339,7 +1339,7 @@
{
return &page->ptl;
}
-#endif /* BLOATED_SPINLOCKS */
+#endif /* ALLOC_SPLIT_PTLOCKS */
static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)
{
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index ad0616f..290901a 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -26,6 +26,7 @@
#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 @@
* 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;
diff --git a/kernel/bounds.c b/kernel/bounds.c
index 5253204..9fd4246 100644
--- a/kernel/bounds.c
+++ b/kernel/bounds.c
@@ -22,6 +22,6 @@
#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 */
}
diff --git a/mm/memory.c b/mm/memory.c
index 5d9025f..b6e211b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4271,7 +4271,7 @@
}
#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;