diff mbox series

[v3,3/5] mm: kmem: make memcg keep a reference to the original objcg

Message ID 20231016221900.4031141-4-roman.gushchin@linux.dev
State New
Headers
Series mm: improve performance of accounted kernel memory allocations |

Commit Message

Roman Gushchin Oct. 16, 2023, 10:18 p.m. UTC 
  Keep a reference to the original objcg object for the entire life
of a memcg structure.

This allows to simplify the synchronization on the kernel memory
allocation paths: pinning a (live) memcg will also pin the
corresponding objcg.

The memory overhead of this change is minimal because object cgroups
usually outlive their corresponding memory cgroups even without this
change, so it's only an additional pointer per memcg.

Signed-off-by: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Acked-by: Shakeel Butt <shakeelb@google.com>
---
 include/linux/memcontrol.h | 8 +++++++-
 mm/memcontrol.c            | 5 +++++
 2 files changed, 12 insertions(+), 1 deletion(-)

Comments

Vlastimil Babka Oct. 18, 2023, 11:58 a.m. UTC | #1 
On 10/17/23 00:18, Roman Gushchin wrote:
> Keep a reference to the original objcg object for the entire life
> of a memcg structure.
> 
> This allows to simplify the synchronization on the kernel memory
> allocation paths: pinning a (live) memcg will also pin the
> corresponding objcg.
> 
> The memory overhead of this change is minimal because object cgroups
> usually outlive their corresponding memory cgroups even without this
> change, so it's only an additional pointer per memcg.
> 
> Signed-off-by: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
> Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> Acked-by: Shakeel Butt <shakeelb@google.com>

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Vlastimil Babka Oct. 18, 2023, 2:06 p.m. UTC | #2 
On 10/17/23 00:18, Roman Gushchin wrote:
> Keep a reference to the original objcg object for the entire life
> of a memcg structure.
> 
> This allows to simplify the synchronization on the kernel memory
> allocation paths: pinning a (live) memcg will also pin the
> corresponding objcg.
> 
> The memory overhead of this change is minimal because object cgroups
> usually outlive their corresponding memory cgroups even without this
> change, so it's only an additional pointer per memcg.
> 
> Signed-off-by: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
> Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> Acked-by: Shakeel Butt <shakeelb@google.com>

Forgot to point out typo:

> ---
>  include/linux/memcontrol.h | 8 +++++++-
>  mm/memcontrol.c            | 5 +++++
>  2 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index ab94ad4597d0..277690af383d 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -299,7 +299,13 @@ struct mem_cgroup {
>  
>  #ifdef CONFIG_MEMCG_KMEM
>  	int kmemcg_id;
> -	struct obj_cgroup __rcu *objcg;
> +	/*
> +	 * memcg->objcg is wiped out as a part of the objcg repaprenting

						reparenting ^

> +	 * process. memcg->orig_objcg preserves a pointer (and a reference)
> +	 * to the original objcg until the end of live of memcg.
> +	 */
> +	struct obj_cgroup __rcu	*objcg;
> +	struct obj_cgroup	*orig_objcg;
>  	/* list of inherited objcgs, protected by objcg_lock */
>  	struct list_head objcg_list;
>  #endif
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 0605e45bd4a2..d90cc19e4113 100644
diff mbox series

Patch

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ab94ad4597d0..277690af383d 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -299,7 +299,13 @@  struct mem_cgroup {
 
 #ifdef CONFIG_MEMCG_KMEM
 	int kmemcg_id;
-	struct obj_cgroup __rcu *objcg;
+	/*
+	 * memcg->objcg is wiped out as a part of the objcg repaprenting
+	 * process. memcg->orig_objcg preserves a pointer (and a reference)
+	 * to the original objcg until the end of live of memcg.
+	 */
+	struct obj_cgroup __rcu	*objcg;
+	struct obj_cgroup	*orig_objcg;
 	/* list of inherited objcgs, protected by objcg_lock */
 	struct list_head objcg_list;
 #endif
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0605e45bd4a2..d90cc19e4113 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3808,6 +3808,8 @@  static int memcg_online_kmem(struct mem_cgroup *memcg)
 
 	objcg->memcg = memcg;
 	rcu_assign_pointer(memcg->objcg, objcg);
+	obj_cgroup_get(objcg);
+	memcg->orig_objcg = objcg;
 
 	static_branch_enable(&memcg_kmem_online_key);
 
@@ -5302,6 +5304,9 @@  static void __mem_cgroup_free(struct mem_cgroup *memcg)
 {
 	int node;
 
+	if (memcg->orig_objcg)
+		obj_cgroup_put(memcg->orig_objcg);
+
 	for_each_node(node)
 		free_mem_cgroup_per_node_info(memcg, node);
 	kfree(memcg->vmstats);