The patch titled
Subject: slub: make sysfs directories for memcg sub-caches optional
has been added to the -mm tree. Its filename is
slub-make-sysfs-directories-for-memcg-sub-caches-optional.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/slub-make-sysfs-directories-for-memcg-sub-caches-optional.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/slub-make-sysfs-directories-for-memcg-sub-caches-optional.patch
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------------------------------------------------------
From: Tejun Heo <tj@xxxxxxxxxx>
Subject: slub: make sysfs directories for memcg sub-caches optional
SLUB creates a per-cache directory under /sys/kernel/slab which hosts a
bunch of debug files. Usually, there aren't that many caches on a system
and this doesn't really matter; however, if memcg is in use, each cache
can have per-cgroup sub-caches. SLUB creates the same directories for
these sub-caches under /sys/kernel/slab/$CACHE/cgroup.
Unfortunately, because there can be a lot of cgroups, active or draining,
the product of the numbers of caches, cgroups and files in each directory
can reach a very high number - hundreds of thousands is commonplace.
Millions and beyond aren't difficult to reach either.
What's under /sys/kernel/slab is primarily for debugging and the
information and control on the a root cache already cover its sub-caches.
While having a separate directory for each sub-cache can be helpful for
development, it doesn't make much sense to pay this amount of overhead by
default.
This patch introduces a boot parameter slub_memcg_sysfs which determines
whether to create sysfs directories for per-memcg sub-caches. It also
adds CONFIG_SLUB_MEMCG_SYSFS_ON which determines the boot parameter's
default value and defaults to 0.
Link: http://lkml.kernel.org/r/20170204145203.GB26958@xxxxxxxxxxxxxxx
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 8 +++
init/Kconfig | 14 ++++++
mm/slub.c | 29 ++++++++++++--
3 files changed, 48 insertions(+), 3 deletions(-)
diff -puN Documentation/admin-guide/kernel-parameters.txt~slub-make-sysfs-directories-for-memcg-sub-caches-optional Documentation/admin-guide/kernel-parameters.txt
--- a/Documentation/admin-guide/kernel-parameters.txt~slub-make-sysfs-directories-for-memcg-sub-caches-optional
+++ a/Documentation/admin-guide/kernel-parameters.txt
@@ -3679,6 +3679,14 @@
last alloc / free. For more information see
Documentation/vm/slub.txt.
+ 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 -puN init/Kconfig~slub-make-sysfs-directories-for-memcg-sub-caches-optional init/Kconfig
--- a/init/Kconfig~slub-make-sysfs-directories-for-memcg-sub-caches-optional
+++ a/init/Kconfig
@@ -1786,6 +1786,20 @@ 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 -puN mm/slub.c~slub-make-sysfs-directories-for-memcg-sub-caches-optional mm/slub.c
--- a/mm/slub.c~slub-make-sysfs-directories-for-memcg-sub-caches-optional
+++ a/mm/slub.c
@@ -4704,6 +4704,22 @@ 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)
{
@@ -5607,8 +5623,14 @@ static int sysfs_slab_add(struct kmem_ca
{
int err;
const char *name;
+ struct kset *kset = cache_kset(s);
int unmergeable = slab_unmergeable(s);
+ if (!kset) {
+ kobject_init(&s->kobj, &slab_ktype);
+ return 0;
+ }
+
if (unmergeable) {
/*
* Slabcache can never be merged so we can use the name proper.
@@ -5625,7 +5647,7 @@ static int sysfs_slab_add(struct kmem_ca
name = create_unique_id(s);
}
- s->kobj.kset = cache_kset(s);
+ s->kobj.kset = kset;
err = kobject_init_and_add(&s->kobj, &slab_ktype, NULL, "%s", name);
if (err)
goto out;
@@ -5635,7 +5657,7 @@ static int sysfs_slab_add(struct kmem_ca
goto out_del_kobj;
#ifdef CONFIG_MEMCG
- if (is_root_cache(s)) {
+ if (is_root_cache(s) && memcg_sysfs_enabled) {
s->memcg_kset = kset_create_and_add("cgroup", NULL, &s->kobj);
if (!s->memcg_kset) {
err = -ENOMEM;
@@ -5677,7 +5699,8 @@ static void sysfs_slab_remove(struct kme
return;
#ifdef CONFIG_MEMCG
- kset_unregister(s->memcg_kset);
+ if (s->memcg_kset)
+ kset_unregister(s->memcg_kset);
#endif
kobject_uevent(&s->kobj, KOBJ_REMOVE);
kobject_del(&s->kobj);
_
Patches currently in -mm which might be from tj@xxxxxxxxxx are
cpumask-use-nr_cpumask_bits-for-parsing-functions.patch
revert-slub-move-synchronize_sched-out-of-slab_mutex-on-shrink.patch
slub-separate-out-sysfs_slab_release-from-sysfs_slab_remove.patch
slab-remove-synchronous-rcu_barrier-call-in-memcg-cache-release-path.patch
slab-reorganize-memcg_cache_params.patch
slab-link-memcg-kmem_caches-on-their-associated-memory-cgroup.patch
slab-implement-slab_root_caches-list.patch
slab-introduce-__kmemcg_cache_deactivate.patch
slab-remove-synchronous-synchronize_sched-from-memcg-cache-deactivation-path.patch
slab-remove-slub-sysfs-interface-files-early-for-empty-memcg-caches.patch
slab-use-memcg_kmem_cache_wq-for-slab-destruction-operations.patch
slub-make-sysfs-directories-for-memcg-sub-caches-optional.patch
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