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From: Christoph Lameter on 3 Aug 2010 23:00
Move the gfpflags masking into the hooks for checkers and into the slowpaths.
gfpflag masking requires access to a global variable and thus adds an
additional cacheline reference to the hotpaths.

If no hooks are active then the gfpflag masking will result in
code that the compiler can toss out.

Signed-off-by: Christoph Lameter <cl(a)linux-foundation.org>

---
mm/slub.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c 2010-07-26 14:26:33.000000000 -0500
+++ linux-2.6/mm/slub.c 2010-07-26 14:26:47.000000000 -0500
@@ -798,6 +798,7 @@ static void trace(struct kmem_cache *s,
*/
static inline int slab_pre_alloc_hook(struct kmem_cache *s, gfp_t flags)
{
+ flags &= gfp_allowed_mask;
lockdep_trace_alloc(flags);
might_sleep_if(flags & __GFP_WAIT);

@@ -806,6 +807,7 @@ static inline int slab_pre_alloc_hook(st

static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags, void *object)
{
+ flags &= gfp_allowed_mask;
kmemcheck_slab_alloc(s, flags, object, s->objsize);
kmemleak_alloc_recursive(object, s->objsize, 1, s->flags, flags);
}
@@ -1679,6 +1681,7 @@ new_slab:
goto load_freelist;
}

+ gfpflags &= gfp_allowed_mask;
if (gfpflags & __GFP_WAIT)
local_irq_enable();

@@ -1727,8 +1730,6 @@ static __always_inline void *slab_alloc(
struct kmem_cache_cpu *c;
unsigned long flags;

- gfpflags &= gfp_allowed_mask;
-
if (!slab_pre_alloc_hook(s, gfpflags))
return NULL;


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Prev: fix corruption of hibernation caused by reusing swap at saving image
Next: [S+Q3 05/23] Subjec Slub: Force no inlining of debug functions