linux-kernel - [PATCH -mm v2] slub: document setting min order with debug_guardpage

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Message-ID: <20120111080320.GA2452@redhat.com>
Date:	Wed, 11 Jan 2012 09:03:32 +0100
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	akpm@...ux-foundation.org
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	David Rientjes <rientjes@...gle.com>,
	linux-kernel@...r.kernel.org, Pekka Enberg <penberg@...helsinki.fi>
Subject: [PATCH -mm v2] slub: document setting min order with
 debug_guardpage_minorder > 0

v1 -> v2:
- remove trailing whitespace
- note debug_guardpage_minorder is a command line parameter
- make clear that writing to /sys/cache/slab/cache/order will have no
  effect with debug_guardpage_minorder > 0

Acked-by: David Rientjes <rientjes@...gle.com>
Cc: Pekka Enberg <penberg@...helsinki.fi>
Cc: "Rafael J. Wysocki" <rjw@...k.pl>
Signed-off-by: Stanislaw Gruszka <sgruszka@...hat.com>
---
 Documentation/ABI/testing/sysfs-kernel-slab |    4 ++++
 Documentation/vm/slub.txt                   |    5 ++++-
 2 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-kernel-slab b/Documentation/ABI/testing/sysfs-kernel-slab
index 8b093f8..91bd6ca 100644
--- a/Documentation/ABI/testing/sysfs-kernel-slab
+++ b/Documentation/ABI/testing/sysfs-kernel-slab
@@ -346,6 +346,10 @@ Description:
 		number of objects per slab.  If a slab cannot be allocated
 		because of fragmentation, SLUB will retry with the minimum order
 		possible depending on its characteristics.
+		When debug_guardpage_minorder=N (N > 0) parameter is specified
+		(see Documentation/kernel-parameters.txt), the minimum possible
+		order is used and this sysfs entry can not be used to change
+		the order at run time.
 
 What:		/sys/kernel/slab/cache/order_fallback
 Date:		April 2008
diff --git a/Documentation/vm/slub.txt b/Documentation/vm/slub.txt
index f464f47..1514d9f 100644
--- a/Documentation/vm/slub.txt
+++ b/Documentation/vm/slub.txt
@@ -131,7 +131,10 @@ slub_min_objects.
 slub_max_order specified the order at which slub_min_objects should no
 longer be checked. This is useful to avoid SLUB trying to generate
 super large order pages to fit slub_min_objects of a slab cache with
-large object sizes into one high order page.
+large object sizes into one high order page. Setting command line
+parameter debug_guardpage_minorder=N (N > 0), forces setting
+slub_max_order to 0, what cause minimum possible order of slabs
+allocation.
 
 SLUB Debug output
 -----------------
-- 
1.7.1

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