github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-11-06 21:58:01 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

memcg: base swap charge accounting on memcgid root status

Browse Source 
A private ID currently pins its original memcg, so testing whether the ID
belongs to root is equivalent to testing whether the resolved memcg is
root.

That equivalence will no longer hold when IDs refer to objcgs.  A non-root
ID may resolve to root after reparenting, but its swap entries still carry
counter charges inherited by root.  Skipping their uncharge based on the
resolved memcg would leave those charges behind.

Use the private ID's root status to decide whether a swap entry carries a
counter charge.  A root-ID entry carries none, while a non-root-ID entry
must release its charge even if its current accounting memcg has become
root.

This patch adds a new helper to check if the memcgid equals to that of the
root memcg.  For swap uncharging and v2 swap charging, simply decide
whether to charge/uncharge memsw or swap counter based on the swap memcgid
is root or not.  For v1 swapout, don't recharge the memsw counter, just
cancel the charge if the swap memcg ID refers to the root memcg.

This makes memory and swap charging have similar semantics: one relys on
the objcg's root status, and the other relys on the memcgid's root status.

Link: https://lore.kernel.org/20260921-bingfangguo-memcgid-rework-v2-2-6c0637dc0edb@tencent.com
Signed-off-by: Bingfang Guo <bingfangguo@tencent.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Muchun Song <muchun.song@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Qi Zheng <qi.zheng@linux.dev>
Cc: Kairui Song <kasong@tencent.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Wei Xu <weixugc@google.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Bingfang Guo <bfguo@icloud.com>
This commit is contained in:
Bingfang Guo 2026-09-21 14:16:25 +08:00 committed by Andrew Morton
parent 127293b445
commit ea74172be2
3 changed files with 15 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
mm/memcontrol-v1.c
View File

@ -271,6 +271,7 @@ void __memcg1_swapout(struct folio *folio, struct swap_cluster_info *ci)
struct mem_cgroup *memcg, *swap_memcg;
struct obj_cgroup *objcg;
unsigned int nr_entries;
unsigned short private_id;
VM_WARN_ON_ONCE_FOLIO(!folio_test_swapcache(folio), folio);
VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
@ -293,25 +294,24 @@ void __memcg1_swapout(struct folio *folio, struct swap_cluster_info *ci)
/*
* In case the memcg owning these pages has been offlined and doesn't
* have an ID allocated to it anymore, charge the closest online
* ancestor for the swap instead and transfer the memory+swap charge.
* ancestor for the swap instead and cancel the memory+swap charge
* if the ID refers to the root memcg.
*/
nr_entries = folio_nr_pages(folio);
swap_memcg = mem_cgroup_private_id_get_online(memcg, nr_entries);
private_id = mem_cgroup_private_id(swap_memcg);
mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries);
__swap_cgroup_set(ci, swp_cluster_offset(folio->swap), nr_entries,
mem_cgroup_private_id(swap_memcg));
__swap_cgroup_set(ci, swp_cluster_offset(folio->swap), nr_entries, private_id);
folio_unqueue_deferred_split(folio);
folio->memcg_data = 0;
if (!obj_cgroup_is_root(objcg))
if (!obj_cgroup_is_root(objcg)) {
page_counter_uncharge(&memcg->memory, nr_entries);
if (memcg != swap_memcg) {
if (!mem_cgroup_is_root(swap_memcg))
page_counter_charge(&swap_memcg->memsw, nr_entries);
page_counter_uncharge(&memcg->memsw, nr_entries);
if (mem_cgroup_private_id_is_root(private_id))
page_counter_uncharge(&memcg->memsw, nr_entries);
}
/*

5
mm/memcontrol-v1.h
View File

@ -22,6 +22,11 @@ void drain_all_stock(struct mem_cgroup *root_memcg);
int memory_stat_show(struct seq_file *m, void *v);
static inline bool mem_cgroup_private_id_is_root(unsigned short id)
{
return id == mem_cgroup_private_id(root_mem_cgroup);
}
struct mem_cgroup *mem_cgroup_private_id_get_online(struct mem_cgroup *memcg,
unsigned int n);

4
mm/memcontrol.c
View File

@ -5975,7 +5975,7 @@ int __mem_cgroup_try_charge_swap(struct folio *folio)
/* memcg is pined by memcg ID. */
private_id = mem_cgroup_private_id(memcg);
if (!mem_cgroup_is_root(memcg) &&
if (!mem_cgroup_private_id_is_root(private_id) &&
!page_counter_try_charge(&memcg->swap, nr_pages, &counter)) {
memcg_memory_event(memcg, MEMCG_SWAP_MAX);
memcg_memory_event(memcg, MEMCG_SWAP_FAIL);
@ -6004,7 +6004,7 @@ void __mem_cgroup_uncharge_swap(unsigned short id, unsigned int nr_pages)
rcu_read_lock();
memcg = mem_cgroup_from_private_id(id);
if (memcg) {
if (!mem_cgroup_is_root(memcg)) {
if (!mem_cgroup_private_id_is_root(id)) {
if (do_memsw_account())
page_counter_uncharge(&memcg->memsw, nr_pages);
else