Proposal for a patch for slub to move the pfmemalloc handling out of the
fastpath by simply not assigning a per cpu slab when pfmemalloc processing
is going on.
Subject: [slub] Fix so that no mods are required for the fast path
Remove the check for pfmemalloc from the alloc hotpath and put the logic after
the election of a new per cpu slab.
For a pfmemalloc page do not use the fast path but force use of the slow
path (which is also used for the debug case).
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
---
mm/slub.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c 2012-02-10 09:58:13.066125970 -0600
+++ linux-2.6/mm/slub.c 2012-02-10 10:06:07.114113000 -0600
@@ -2273,11 +2273,12 @@ new_slab:
}
}
- if (likely(!kmem_cache_debug(s)))
+ if (likely(!kmem_cache_debug(s) && pfmemalloc_match(c, gfpflags)))
goto load_freelist;
+
/* Only entered in the debug case */
- if (!alloc_debug_processing(s, c->page, object, addr))
+ if (kmem_cache_debug(s) && !alloc_debug_processing(s, c->page, object, addr))
goto new_slab; /* Slab failed checks. Next slab needed */
c->freelist = get_freepointer(s, object);
@@ -2327,8 +2328,7 @@ redo:
barrier();
object = c->freelist;
- if (unlikely(!object || !node_match(c, node) ||
- !pfmemalloc_match(c, gfpflags)))
+ if (unlikely(!object || !node_match(c, node)))
object = __slab_alloc(s, gfpflags, node, addr, c);
else {
--
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