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mm: kmem: make memcg keep a reference to the original objcg 

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.

Link: https://lkml.kernel.org/r/20231019225346.1822282-4-roman.gushchin@linux.dev
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>
Cc: David Rientjes <rientjes@google.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Roman Gushchin 2023-10-19 15:53:43 -07:00 committed by Andrew Morton
parent 1aacbd3543
commit 675d6c9b59
2 changed files with 12 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/memcontrol.h
View File

@ -289,7 +289,13 @@ 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

5
mm/memcontrol.c
View File

@ -3899,6 +3899,8 @@ 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);
@ -5406,6 +5408,9 @@ 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);