linux-kernel - [PATCH v2] mm/slab_common: provide "slab_merge" option for !IS_ENABLED(CONFIG_SLAB_MERGE

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Date:   Fri, 19 Mar 2021 15:45:03 -0400
From:   Rafael Aquini <aquini@...hat.com>
To:     linux-mm@...ck.org
Cc:     Jonathan Corbet <corbet@....net>, Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] mm/slab_common: provide "slab_merge" option for !IS_ENABLED(CONFIG_SLAB_MERGE_DEFAULT) builds

This is a minor addition to the allocator setup options to provide
a simple way to on demand enable back cache merging for builds
that by default run with CONFIG_SLAB_MERGE_DEFAULT not set.

Signed-off-by: Rafael Aquini <aquini@...hat.com>
---
v2 changelog:
* fix __setup("slab_merge", setup_slab_nomerge); typo

 Documentation/admin-guide/kernel-parameters.txt | 7 +++++++
 mm/slab_common.c                                | 8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 04545725f187..06519eecbfec 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4877,6 +4877,10 @@
 
 	slram=		[HW,MTD]
 
+	slab_merge	[MM]
+			Enable merging of slabs with similar size when the
+			kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
+
 	slab_nomerge	[MM]
 			Disable merging of slabs with similar size. May be
 			necessary if there is some reason to distinguish
@@ -4924,6 +4928,9 @@
 			lower than slub_max_order.
 			For more information see Documentation/vm/slub.rst.
 
+	slub_merge	[MM, SLUB]
+			Same with slab_merge.
+
 	slub_nomerge	[MM, SLUB]
 			Same with slab_nomerge. This is supported for legacy.
 			See slab_nomerge for more information.
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 88e833986332..b84dd734b75f 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -71,11 +71,19 @@ static int __init setup_slab_nomerge(char *str)
 	return 1;
 }
 
+static int __init setup_slab_merge(char *str)
+{
+	slab_nomerge = false;
+	return 1;
+}
+
 #ifdef CONFIG_SLUB
 __setup_param("slub_nomerge", slub_nomerge, setup_slab_nomerge, 0);
+__setup_param("slub_merge", slub_merge, setup_slab_merge, 0);
 #endif
 
 __setup("slab_nomerge", setup_slab_nomerge);
+__setup("slab_merge", setup_slab_merge);
 
 /*
  * Determine the size of a slab object
-- 
2.26.2