mm: micro-optimise slab to avoid a function call

Getting and putting objects in SLAB currently requires a function call but
the bulk of the work is related to PFMEMALLOC reserves which are only
consumed when network-backed storage is critical.  Use an inline function
to determine if the function call is required.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: David Miller <davem@davemloft.net>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 26 insertions, 2 deletions

diff --git a/mm/slab.c b/mm/slab.c
index 77be18dab73c..f8b0d539b482 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -118,6 +118,8 @@
 #include        <linux/memory.h>
 #include        <linux/prefetch.h>
 
+#include        <net/sock.h>
+
 #include        <asm/cacheflush.h>
 #include        <asm/tlbflush.h>
 #include        <asm/page.h>
@@ -965,7 +967,7 @@ out:
         spin_unlock_irqrestore(&l3->list_lock, flags);
 }
 
-static void *ac_get_obj(struct kmem_cache *cachep, struct array_cache *ac,
+static void *__ac_get_obj(struct kmem_cache *cachep, struct array_cache *ac,
                                                 gfp_t flags, bool force_refill)
 {
         int i;
@@ -1012,7 +1014,20 @@ static void *ac_get_obj(struct kmem_cache *cachep, struct array_cache *ac,
         return objp;
 }
 
-static void ac_put_obj(struct kmem_cache *cachep, struct array_cache *ac,
+static inline void *ac_get_obj(struct kmem_cache *cachep,
+                        struct array_cache *ac, gfp_t flags, bool force_refill)
+{
+        void *objp;
+
+        if (unlikely(sk_memalloc_socks()))
+                objp = __ac_get_obj(cachep, ac, flags, force_refill);
+        else
+                objp = ac->entry[--ac->avail];
+
+        return objp;
+}
+
+static void *__ac_put_obj(struct kmem_cache *cachep, struct array_cache *ac,
                                                                 void *objp)
 {
         if (unlikely(pfmemalloc_active)) {
@@ -1022,6 +1037,15 @@ static void ac_put_obj(struct kmem_cache *cachep, struct array_cache *ac,
                         set_obj_pfmemalloc(&objp);
         }
 
+        return objp;
+}
+
+static inline void ac_put_obj(struct kmem_cache *cachep, struct array_cache *ac,
+                                                                void *objp)
+{
+        if (unlikely(sk_memalloc_socks()))
+                objp = __ac_put_obj(cachep, ac, objp);
+
         ac->entry[ac->avail++] = objp;
 }