* [PATCH] slub: make sysfs directories for memcg sub-caches optional
@ 2017-02-04 14:52 ` Tejun Heo
0 siblings, 0 replies; 8+ messages in thread
From: Tejun Heo @ 2017-02-04 14:52 UTC (permalink / raw)
To: Andrew Morton, Christoph Lameter, Pekka Enberg, David Rientjes,
Joonsoo Kim, Vladimir Davydov
Cc: linux-kernel, linux-mm, cgroups, Michal Hocko, kernel-team
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.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
---
Documentation/kernel-parameters.txt | 8 ++++++++
init/Kconfig | 14 ++++++++++++++
mm/slub.c | 29 ++++++++++++++++++++++++++---
3 files changed, 48 insertions(+), 3 deletions(-)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3517,6 +3517,14 @@ bytes respectively. Such letter suffixes
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
--- a/init/Kconfig
+++ b/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
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4700,6 +4700,22 @@ 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)
{
@@ -5603,8 +5619,14 @@ 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.
@@ -5621,7 +5643,7 @@ 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;
@@ -5631,7 +5653,7 @@ 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;
@@ -5673,7 +5695,8 @@ 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);
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH] slub: make sysfs directories for memcg sub-caches optional
@ 2017-02-04 14:52 ` Tejun Heo
0 siblings, 0 replies; 8+ messages in thread
From: Tejun Heo @ 2017-02-04 14:52 UTC (permalink / raw)
To: Andrew Morton, Christoph Lameter, Pekka Enberg, David Rientjes,
Joonsoo Kim, Vladimir Davydov
Cc: linux-kernel, linux-mm, cgroups, Michal Hocko, kernel-team
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.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
---
Documentation/kernel-parameters.txt | 8 ++++++++
init/Kconfig | 14 ++++++++++++++
mm/slub.c | 29 ++++++++++++++++++++++++++---
3 files changed, 48 insertions(+), 3 deletions(-)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3517,6 +3517,14 @@ bytes respectively. Such letter suffixes
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
--- a/init/Kconfig
+++ b/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
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4700,6 +4700,22 @@ 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)
{
@@ -5603,8 +5619,14 @@ 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.
@@ -5621,7 +5643,7 @@ 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;
@@ -5631,7 +5653,7 @@ 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;
@@ -5673,7 +5695,8 @@ 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);
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH] slub: make sysfs directories for memcg sub-caches optional
@ 2017-02-04 14:52 ` Tejun Heo
0 siblings, 0 replies; 8+ messages in thread
From: Tejun Heo @ 2017-02-04 14:52 UTC (permalink / raw)
To: Andrew Morton, Christoph Lameter, Pekka Enberg, David Rientjes,
Joonsoo Kim, Vladimir Davydov
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg, cgroups-u79uwXL29TY76Z2rM5mHXA,
Michal Hocko, kernel-team-b10kYP2dOMg
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.
Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Christoph Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>
Cc: Pekka Enberg <penberg-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: Joonsoo Kim <iamjoonsoo.kim-Hm3cg6mZ9cc@public.gmane.org>
Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Cc: Vladimir Davydov <vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
Documentation/kernel-parameters.txt | 8 ++++++++
init/Kconfig | 14 ++++++++++++++
mm/slub.c | 29 ++++++++++++++++++++++++++---
3 files changed, 48 insertions(+), 3 deletions(-)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3517,6 +3517,14 @@ bytes respectively. Such letter suffixes
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
--- a/init/Kconfig
+++ b/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
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4700,6 +4700,22 @@ 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)
{
@@ -5603,8 +5619,14 @@ 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.
@@ -5621,7 +5643,7 @@ 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;
@@ -5631,7 +5653,7 @@ 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;
@@ -5673,7 +5695,8 @@ 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);
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] slub: make sysfs directories for memcg sub-caches optional
2017-02-04 14:52 ` Tejun Heo
@ 2017-02-07 0:22 ` Andrew Morton
-1 siblings, 0 replies; 8+ messages in thread
From: Andrew Morton @ 2017-02-07 0:22 UTC (permalink / raw)
To: Tejun Heo
Cc: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Vladimir Davydov, linux-kernel, linux-mm, cgroups, Michal Hocko,
kernel-team
On Sat, 4 Feb 2017 09:52:03 -0500 Tejun Heo <tj@kernel.org> wrote:
> 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.
>
> ...
>
> #ifdef CONFIG_MEMCG
> - if (is_root_cache(s)) {
> + if (is_root_cache(s) && memcg_sysfs_enabled) {
This could be turned on and off after bootup but I guess the result
could be pretty confusing.
However there would be useful use cases? The user would normally have
this disabled but if he wants to do a bit of debugging then turn this
on, create a memcg, have a poke around then turn the feature off again.
> s->memcg_kset = kset_create_and_add("cgroup", NULL, &s->kobj);
> if (!s->memcg_kset) {
> err = -ENOMEM;
> @@ -5673,7 +5695,8 @@ 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);
kset_unregister(NULL) is legal
--- a/mm/slub.c~slub-make-sysfs-directories-for-memcg-sub-caches-optional-fix
+++ a/mm/slub.c
@@ -5699,8 +5699,7 @@ static void sysfs_slab_remove(struct kme
return;
#ifdef CONFIG_MEMCG
- if (s->memcg_kset)
- kset_unregister(s->memcg_kset);
+ kset_unregister(s->memcg_kset);
#endif
kobject_uevent(&s->kobj, KOBJ_REMOVE);
kobject_del(&s->kobj);
_
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] slub: make sysfs directories for memcg sub-caches optional
@ 2017-02-07 0:22 ` Andrew Morton
0 siblings, 0 replies; 8+ messages in thread
From: Andrew Morton @ 2017-02-07 0:22 UTC (permalink / raw)
To: Tejun Heo
Cc: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Vladimir Davydov, linux-kernel, linux-mm, cgroups, Michal Hocko,
kernel-team
On Sat, 4 Feb 2017 09:52:03 -0500 Tejun Heo <tj@kernel.org> wrote:
> 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.
>
> ...
>
> #ifdef CONFIG_MEMCG
> - if (is_root_cache(s)) {
> + if (is_root_cache(s) && memcg_sysfs_enabled) {
This could be turned on and off after bootup but I guess the result
could be pretty confusing.
However there would be useful use cases? The user would normally have
this disabled but if he wants to do a bit of debugging then turn this
on, create a memcg, have a poke around then turn the feature off again.
> s->memcg_kset = kset_create_and_add("cgroup", NULL, &s->kobj);
> if (!s->memcg_kset) {
> err = -ENOMEM;
> @@ -5673,7 +5695,8 @@ 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);
kset_unregister(NULL) is legal
--- a/mm/slub.c~slub-make-sysfs-directories-for-memcg-sub-caches-optional-fix
+++ a/mm/slub.c
@@ -5699,8 +5699,7 @@ static void sysfs_slab_remove(struct kme
return;
#ifdef CONFIG_MEMCG
- if (s->memcg_kset)
- kset_unregister(s->memcg_kset);
+ kset_unregister(s->memcg_kset);
#endif
kobject_uevent(&s->kobj, KOBJ_REMOVE);
kobject_del(&s->kobj);
_
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] slub: make sysfs directories for memcg sub-caches optional
2017-02-07 0:22 ` Andrew Morton
(?)
@ 2017-02-07 17:10 ` Tejun Heo
-1 siblings, 0 replies; 8+ messages in thread
From: Tejun Heo @ 2017-02-07 17:10 UTC (permalink / raw)
To: Andrew Morton
Cc: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Vladimir Davydov, linux-kernel, linux-mm, cgroups, Michal Hocko,
kernel-team
Hello, Andrew.
On Mon, Feb 06, 2017 at 04:22:13PM -0800, Andrew Morton wrote:
> > #ifdef CONFIG_MEMCG
> > - if (is_root_cache(s)) {
> > + if (is_root_cache(s) && memcg_sysfs_enabled) {
>
> This could be turned on and off after bootup but I guess the result
> could be pretty confusing.
>
> However there would be useful use cases? The user would normally have
> this disabled but if he wants to do a bit of debugging then turn this
> on, create a memcg, have a poke around then turn the feature off again.
Hmm... maybe. It's somewhat nasty to do after-the-fact. You would
have to re-walk all the caches to create and destroy the sysfs
entries. Given that it's a pretty fringe debug feature, I'm not sure
the added complexity would be justified.
> > s->memcg_kset = kset_create_and_add("cgroup", NULL, &s->kobj);
> > if (!s->memcg_kset) {
> > err = -ENOMEM;
> > @@ -5673,7 +5695,8 @@ 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);
>
> kset_unregister(NULL) is legal
>
> --- a/mm/slub.c~slub-make-sysfs-directories-for-memcg-sub-caches-optional-fix
> +++ a/mm/slub.c
> @@ -5699,8 +5699,7 @@ static void sysfs_slab_remove(struct kme
> return;
>
> #ifdef CONFIG_MEMCG
> - if (s->memcg_kset)
> - kset_unregister(s->memcg_kset);
> + kset_unregister(s->memcg_kset);
> #endif
> kobject_uevent(&s->kobj, KOBJ_REMOVE);
> kobject_del(&s->kobj);
Ah, of course, looks good to me.
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] slub: make sysfs directories for memcg sub-caches optional
@ 2017-02-07 17:10 ` Tejun Heo
0 siblings, 0 replies; 8+ messages in thread
From: Tejun Heo @ 2017-02-07 17:10 UTC (permalink / raw)
To: Andrew Morton
Cc: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Vladimir Davydov, linux-kernel, linux-mm, cgroups, Michal Hocko,
kernel-team
Hello, Andrew.
On Mon, Feb 06, 2017 at 04:22:13PM -0800, Andrew Morton wrote:
> > #ifdef CONFIG_MEMCG
> > - if (is_root_cache(s)) {
> > + if (is_root_cache(s) && memcg_sysfs_enabled) {
>
> This could be turned on and off after bootup but I guess the result
> could be pretty confusing.
>
> However there would be useful use cases? The user would normally have
> this disabled but if he wants to do a bit of debugging then turn this
> on, create a memcg, have a poke around then turn the feature off again.
Hmm... maybe. It's somewhat nasty to do after-the-fact. You would
have to re-walk all the caches to create and destroy the sysfs
entries. Given that it's a pretty fringe debug feature, I'm not sure
the added complexity would be justified.
> > s->memcg_kset = kset_create_and_add("cgroup", NULL, &s->kobj);
> > if (!s->memcg_kset) {
> > err = -ENOMEM;
> > @@ -5673,7 +5695,8 @@ 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);
>
> kset_unregister(NULL) is legal
>
> --- a/mm/slub.c~slub-make-sysfs-directories-for-memcg-sub-caches-optional-fix
> +++ a/mm/slub.c
> @@ -5699,8 +5699,7 @@ static void sysfs_slab_remove(struct kme
> return;
>
> #ifdef CONFIG_MEMCG
> - if (s->memcg_kset)
> - kset_unregister(s->memcg_kset);
> + kset_unregister(s->memcg_kset);
> #endif
> kobject_uevent(&s->kobj, KOBJ_REMOVE);
> kobject_del(&s->kobj);
Ah, of course, looks good to me.
Thanks.
--
tejun
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] slub: make sysfs directories for memcg sub-caches optional
@ 2017-02-07 17:10 ` Tejun Heo
0 siblings, 0 replies; 8+ messages in thread
From: Tejun Heo @ 2017-02-07 17:10 UTC (permalink / raw)
To: Andrew Morton
Cc: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Vladimir Davydov, linux-kernel-u79uwXL29TY76Z2rM5mHXA,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg, cgroups-u79uwXL29TY76Z2rM5mHXA,
Michal Hocko, kernel-team-b10kYP2dOMg
Hello, Andrew.
On Mon, Feb 06, 2017 at 04:22:13PM -0800, Andrew Morton wrote:
> > #ifdef CONFIG_MEMCG
> > - if (is_root_cache(s)) {
> > + if (is_root_cache(s) && memcg_sysfs_enabled) {
>
> This could be turned on and off after bootup but I guess the result
> could be pretty confusing.
>
> However there would be useful use cases? The user would normally have
> this disabled but if he wants to do a bit of debugging then turn this
> on, create a memcg, have a poke around then turn the feature off again.
Hmm... maybe. It's somewhat nasty to do after-the-fact. You would
have to re-walk all the caches to create and destroy the sysfs
entries. Given that it's a pretty fringe debug feature, I'm not sure
the added complexity would be justified.
> > s->memcg_kset = kset_create_and_add("cgroup", NULL, &s->kobj);
> > if (!s->memcg_kset) {
> > err = -ENOMEM;
> > @@ -5673,7 +5695,8 @@ 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);
>
> kset_unregister(NULL) is legal
>
> --- a/mm/slub.c~slub-make-sysfs-directories-for-memcg-sub-caches-optional-fix
> +++ a/mm/slub.c
> @@ -5699,8 +5699,7 @@ static void sysfs_slab_remove(struct kme
> return;
>
> #ifdef CONFIG_MEMCG
> - if (s->memcg_kset)
> - kset_unregister(s->memcg_kset);
> + kset_unregister(s->memcg_kset);
> #endif
> kobject_uevent(&s->kobj, KOBJ_REMOVE);
> kobject_del(&s->kobj);
Ah, of course, looks good to me.
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2017-02-07 17:10 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-02-04 14:52 [PATCH] slub: make sysfs directories for memcg sub-caches optional Tejun Heo
2017-02-04 14:52 ` Tejun Heo
2017-02-04 14:52 ` Tejun Heo
2017-02-07 0:22 ` Andrew Morton
2017-02-07 0:22 ` Andrew Morton
2017-02-07 17:10 ` Tejun Heo
2017-02-07 17:10 ` Tejun Heo
2017-02-07 17:10 ` Tejun Heo
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.