config ARCH_HAVE_NMI_SAFE_CMPXCHG
bool
+config HAVE_ALIGNED_STRUCT_PAGE
+ bool
+ help
+ This makes sure that struct pages are double word aligned and that
+ e.g. the SLUB allocator can perform double word atomic operations
+ on a struct page for better performance. However selecting this
+ might increase the size of a struct page by a word.
+
source "kernel/gcov/Kconfig"
select PERF_EVENTS
select HAVE_PERF_EVENTS_NMI
select ANON_INODES
+ select HAVE_ALIGNED_STRUCT_PAGE if SLUB && !M386
select HAVE_ARCH_KMEMCHECK
select HAVE_USER_RETURN_NOTIFIER
select HAVE_ARCH_JUMP_LABEL
#endif
}
/*
- * If another subsystem starts using the double word pairing for atomic
- * operations on struct page then it must change the #if to ensure
- * proper alignment of the page struct.
+ * The struct page can be forced to be double word aligned so that atomic ops
+ * on double words work. The SLUB allocator can make use of such a feature.
*/
-#if defined(CONFIG_SLUB) && defined(CONFIG_CMPXCHG_LOCAL)
- __attribute__((__aligned__(2*sizeof(unsigned long))))
+#ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE
+ __aligned(2 * sizeof(unsigned long))
#endif
;
const char *n)
{
VM_BUG_ON(!irqs_disabled());
-#ifdef CONFIG_CMPXCHG_DOUBLE
+#if defined(CONFIG_CMPXCHG_DOUBLE) && defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
if (s->flags & __CMPXCHG_DOUBLE) {
if (cmpxchg_double(&page->freelist,
freelist_old, counters_old,
void *freelist_new, unsigned long counters_new,
const char *n)
{
-#ifdef CONFIG_CMPXCHG_DOUBLE
+#if defined(CONFIG_CMPXCHG_DOUBLE) && defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
if (s->flags & __CMPXCHG_DOUBLE) {
if (cmpxchg_double(&page->freelist,
freelist_old, counters_old,
}
}
-#ifdef CONFIG_CMPXCHG_DOUBLE
+#if defined(CONFIG_CMPXCHG_DOUBLE) && defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
if (system_has_cmpxchg_double() && (s->flags & SLAB_DEBUG_FLAGS) == 0)
/* Enable fast mode */
s->flags |= __CMPXCHG_DOUBLE;