linux-kernel - [RFC 3/3] slub: min order when corrupt

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Message-Id: <1318861486-3942-3-git-send-email-sgruszka@redhat.com>
Date:	Mon, 17 Oct 2011 16:24:46 +0200
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	linux-mm@...ck.org
Cc:	linux-kernel@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Stanislaw Gruszka <sgruszka@...hat.com>
Subject: [RFC 3/3] slub: min order when corrupt_dbg

Disable slub debug facilities and allocate slabs at minimal order when
corrupt_dbg > 0 to increase probability to catch random memory
corruption by cpu exception.

Signed-off-by: Stanislaw Gruszka <sgruszka@...hat.com>
---
 mm/slub.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 7c54fe8..fec88b5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2755,7 +2755,7 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
 	unsigned long flags = s->flags;
 	unsigned long size = s->objsize;
 	unsigned long align = s->align;
-	int order;
+	int order, min_order;
 
 	/*
 	 * Round up object size to the next word boundary. We can only
@@ -2840,8 +2840,11 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
 	 */
 	size = ALIGN(size, align);
 	s->size = size;
+	min_order = get_order(size);
 	if (forced_order >= 0)
 		order = forced_order;
+	else if (corrupt_dbg())
+		order = min_order;
 	else
 		order = calculate_order(size, s->reserved);
 
@@ -2862,7 +2865,7 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
 	 * Determine the number of objects per slab
 	 */
 	s->oo = oo_make(order, size, s->reserved);
-	s->min = oo_make(get_order(size), size, s->reserved);
+	s->min = oo_make(min_order, size, s->reserved);
 	if (oo_objects(s->oo) > oo_objects(s->max))
 		s->max = s->oo;
 
@@ -3529,6 +3532,9 @@ void __init kmem_cache_init(void)
 	struct kmem_cache *temp_kmem_cache_node;
 	unsigned long kmalloc_size;
 
+	if (corrupt_dbg())
+		slub_debug = 0;
+
 	kmem_size = offsetof(struct kmem_cache, node) +
 				nr_node_ids * sizeof(struct kmem_cache_node *);
 
-- 
1.7.1

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