The commit is pushed to "branch-rh7-3.10.0-1160.90.1.vz7.200.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1160.90.1.vz7.200.4
------>
commit d0f735e5df66207ef30de23668b5f19b7c16a212
Author: Johannes Weiner <han...@cmpxchg.org>
Date: Wed Jul 5 14:39:44 2023 +0800
ms/mm: memcontrol: uncharge pages on swapout
This series gets rid of the remaining page_cgroup flags, thus cutting the
memcg per-page overhead down to one pointer.
This patch (of 4):
mem_cgroup_swapout() is called with exclusive access to the page at the
end of the page's lifetime. Instead of clearing the PCG_MEMSW flag and
deferring the uncharge, just do it right away. This allows follow-up
patches to simplify the uncharge code.
Signed-off-by: Johannes Weiner <han...@cmpxchg.org>
Cc: Hugh Dickins <hu...@google.com>
Acked-by: Michal Hocko <mho...@suse.cz>
Acked-by: Vladimir Davydov <vdavy...@parallels.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hir...@jp.fujitsu.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
https://jira.vzint.dev/browse/PSBM-147036
(cherry picked from commit 7bdd143c37e591c254d0991ac398a53f3f9ef1af)
Signed-off-by: Pavel Tikhomirov <ptikhomi...@virtuozzo.com>
=================
Patchset description:
memcg: release id when offlinging cgroup
We see that container user can deplete memory cgroup ids on the system
(64k) and prevent further memory cgroup creation. In crash collected by
our customer in such a situation we see that mem_cgroup_idr is full of
cgroups from one container with same exact path (cgroup of docker
service), cgroups are not released because they have kmem charges, this
kmem charge is for a tmpfs dentry allocated from this cgroup. (And on
vz7 kernel it seems that such a dentry is only released after umounting
tmpfs or removing the corresponding file from tmpfs.)
So there is a valid way to hold kmem cgroup for a long time. Similar
thing was mentioned in mainstream with page cache holding kmem cgroup
for a long time. And they proposed a way to deal with it - just release
cgroup id early so that one can allocate new cgroups immediately.
Reproduce:
https://git.vzint.dev/users/ptikhomirov/repos/helpers/browse/memcg-related/test-mycg-tmpfs.sh
After this fix the number of memory cgroups in /proc/cgroups can now
show > 64k as we allow to leave memory cgroups hanging while releasing
their ids.
Note: Maybe it's a bad idea to allow container to eat kernel
memory with such a hanging cgroups, but yet I don't have better ideas.
https://jira.vzint.dev/browse/PSBM-147473
https://jira.vzint.dev/browse/PSBM-147036
---
mm/memcontrol.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7135306c6ac0..99e0dbfe8f77 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7738,6 +7738,7 @@ static void __init enable_swap_cgroup(void)
*/
void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
{
+ struct mem_cgroup *memcg;
struct page_cgroup *pc;
unsigned short oldid;
@@ -7754,14 +7755,23 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t
entry)
return;
VM_BUG_ON_PAGE(!(pc->flags & PCG_MEMSW), page);
+ memcg = pc->mem_cgroup;
- oldid = swap_cgroup_record(entry, mem_cgroup_id(pc->mem_cgroup));
+ oldid = swap_cgroup_record(entry, mem_cgroup_id(memcg));
VM_BUG_ON_PAGE(oldid, page);
+ mem_cgroup_swap_statistics(memcg, true);
+ this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PSWPOUT]);
+
+ pc->flags = 0;
- pc->flags &= ~PCG_MEMSW;
- css_get(&pc->mem_cgroup->css);
- mem_cgroup_swap_statistics(pc->mem_cgroup, true);
- this_cpu_inc(pc->mem_cgroup->stat->events[MEM_CGROUP_EVENTS_PSWPOUT]);
+ if (!mem_cgroup_is_root(memcg))
+ page_counter_uncharge(&memcg->memory, 1);
+
+ /* XXX: caller holds IRQ-safe mapping->tree_lock */
+ VM_BUG_ON(!irqs_disabled());
+
+ mem_cgroup_charge_statistics(memcg, page, -1);
+ memcg_check_events(memcg, page);
}
/**
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