linux-kernel - [PATCH] mm, slub: remove slub_memcg_sysfs boot param and CONFIG_SLUB_MEMCG_SYSFS

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Date:   Wed, 27 Jan 2021 13:47:45 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     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>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Roman Gushchin <guro@...com>, Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH] mm, slub: remove slub_memcg_sysfs boot param and CONFIG_SLUB_MEMCG_SYSFS_ON

The boot param and config determine the value of memcg_sysfs_enabled, which is
unused since commit 10befea91b61 ("mm: memcg/slab: use a single set of
kmem_caches for all allocations") as there are no per-memcg kmem caches
anymore.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 Documentation/admin-guide/kernel-parameters.txt |  8 --------
 init/Kconfig                                    | 14 --------------
 mm/slub.c                                       | 16 ----------------
 3 files changed, 38 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f4497faef266..7dc351da0005 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4892,14 +4892,6 @@
 			last alloc / free. For more information see
 			Documentation/vm/slub.rst.
 
-	slub_memcg_sysfs=	[MM, SLUB]
-			Determines whether to enable sysfs directories for
-			memory cgroup sub-caches. 1 to enable, 0 to disable.
-			The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
-			Enabling this can lead to a very high number of	debug
-			directories and files being created under
-			/sys/kernel/slub.
-
 	slub_max_order= [MM, SLUB]
 			Determines the maximum allowed order for slabs.
 			A high setting may cause OOMs due to memory
diff --git a/init/Kconfig b/init/Kconfig
index e4e2932da237..af454a51f3c5 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1851,20 +1851,6 @@ config SLUB_DEBUG
 	  SLUB sysfs support. /sys/slab will not exist and there will be
 	  no support for cache validation etc.
 
-config SLUB_MEMCG_SYSFS_ON
-	default n
-	bool "Enable memcg SLUB sysfs support by default" if EXPERT
-	depends on SLUB && SYSFS && MEMCG
-	help
-	  SLUB creates a directory under /sys/kernel/slab for each
-	  allocation cache to host info and debug files. If memory
-	  cgroup is enabled, each cache can have per memory cgroup
-	  caches. SLUB can create the same sysfs directories for these
-	  caches under /sys/kernel/slab/CACHE/cgroup but it can lead
-	  to a very high number of debug files being created. This is
-	  controlled by slub_memcg_sysfs boot parameter and this
-	  config option determines the parameter's default value.
-
 config COMPAT_BRK
 	bool "Disable heap randomization"
 	default y
diff --git a/mm/slub.c b/mm/slub.c
index 1b5148747c64..88782727412c 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5040,22 +5040,6 @@ enum slab_stat_type {
 #define SO_OBJECTS	(1 << SL_OBJECTS)
 #define SO_TOTAL	(1 << SL_TOTAL)
 
-#ifdef CONFIG_MEMCG
-static bool memcg_sysfs_enabled = IS_ENABLED(CONFIG_SLUB_MEMCG_SYSFS_ON);
-
-static int __init setup_slub_memcg_sysfs(char *str)
-{
-	int v;
-
-	if (get_option(&str, &v) > 0)
-		memcg_sysfs_enabled = v;
-
-	return 1;
-}
-
-__setup("slub_memcg_sysfs=", setup_slub_memcg_sysfs);
-#endif
-
 static ssize_t show_slab_objects(struct kmem_cache *s,
 				 char *buf, unsigned long flags)
 {
-- 
2.30.0