linux-kernel - [PATCH 10/16] mm/slab: align cache size first before determination of OFF

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Message-Id: <1452749069-15334-11-git-send-email-iamjoonsoo.kim@lge.com>
Date:	Thu, 14 Jan 2016 14:24:23 +0900
From:	Joonsoo Kim <js1304@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH 10/16] mm/slab: align cache size first before determination of OFF_SLAB candidate

Finding suitable OFF_SLAB candidate is more related to aligned cache size
rather than original size. Same reasoning can be applied to
the debug pagealloc candidate. So, this patch moves up alignment fixup
to proper position.

>From that point, size is aligned so we can remove some alignment fixups.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
---
 mm/slab.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index fe17acc..3a319f5 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2126,6 +2126,17 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 		else
 			size += BYTES_PER_WORD;
 	}
+#endif
+
+	size = ALIGN(size, cachep->align);
+	/*
+	 * We should restrict the number of objects in a slab to implement
+	 * byte sized index. Refer comment on SLAB_OBJ_MIN_SIZE definition.
+	 */
+	if (FREELIST_BYTE_INDEX && size < SLAB_OBJ_MIN_SIZE)
+		size = ALIGN(SLAB_OBJ_MIN_SIZE, cachep->align);
+
+#if DEBUG
 	/*
 	 * To activate debug pagealloc, off-slab management is necessary
 	 * requirement. In early phase of initialization, small sized slab
@@ -2136,8 +2147,8 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 	if (debug_pagealloc_enabled() && (flags & SLAB_POISON) &&
 		!slab_early_init && size >= kmalloc_size(INDEX_NODE) &&
 		size >= 256 && cachep->object_size > cache_line_size() &&
-		ALIGN(size, cachep->align) < PAGE_SIZE) {
-		cachep->obj_offset += PAGE_SIZE - ALIGN(size, cachep->align);
+		size < PAGE_SIZE) {
+		cachep->obj_offset += PAGE_SIZE - size;
 		size = PAGE_SIZE;
 	}
 #endif
@@ -2149,20 +2160,13 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 	 * SLAB_NOLEAKTRACE to avoid recursive calls into kmemleak)
 	 */
 	if (size >= OFF_SLAB_MIN_SIZE && !slab_early_init &&
-	    !(flags & SLAB_NOLEAKTRACE))
+	    !(flags & SLAB_NOLEAKTRACE)) {
 		/*
 		 * Size is large, assume best to place the slab management obj
 		 * off-slab (should allow better packing of objs).
 		 */
 		flags |= CFLGS_OFF_SLAB;
-
-	size = ALIGN(size, cachep->align);
-	/*
-	 * We should restrict the number of objects in a slab to implement
-	 * byte sized index. Refer comment on SLAB_OBJ_MIN_SIZE definition.
-	 */
-	if (FREELIST_BYTE_INDEX && size < SLAB_OBJ_MIN_SIZE)
-		size = ALIGN(SLAB_OBJ_MIN_SIZE, cachep->align);
+	}
 
 	left_over = calculate_slab_order(cachep, size, flags);
 
-- 
1.9.1