Messages in this thread | | | Date | Tue, 2 Mar 2021 16:51:05 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH] mm/memcg: set memcg when split pages |
| |
On Tue 02-03-21 10:17:03, Michal Hocko wrote: > [Cc Johannes for awareness and fixup Nick's email] > > On Tue 02-03-21 01:34:51, Zhou Guanghui wrote: > > When split page, the memory cgroup info recorded in first page is > > not copied to tail pages. In this case, when the tail pages are > > freed, the uncharge operation is not performed. As a result, the > > usage of this memcg keeps increasing, and the OOM may occur. > > > > So, the copying of first page's memory cgroup info to tail pages > > is needed when split page. > > I was not aware that alloc_pages_exact is used for accounted allocations > but git grep told me otherwise so this is not a theoretical one. Both > users (arm64 and s390 kvm) are quite recent AFAICS. split_page is also > used in dma allocator but I got lost in indirection so I have no idea > whether there are any users there. > > The page itself looks reasonable to me. > > > Signed-off-by: Zhou Guanghui <zhouguanghui1@huawei.com> > > Acked-by: Michal Hocko <mhocko@suse.com> > > Minor nit > > > --- > > include/linux/memcontrol.h | 10 ++++++++++ > > mm/page_alloc.c | 4 +++- > > 2 files changed, 13 insertions(+), 1 deletion(-) > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > index e6dc793d587d..c7e2b4421dc1 100644 > > --- a/include/linux/memcontrol.h > > +++ b/include/linux/memcontrol.h > > @@ -867,6 +867,12 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg); > > extern bool cgroup_memory_noswap; > > #endif > > > > +static inline void copy_page_memcg(struct page *dst, struct page *src) > > +{ > > + if (src->memcg_data) > > + dst->memcg_data = src->memcg_data; > > I would just drop the test. The struct page is a single cache line which > is dirty by the reference count so another store will unlikely be > noticeable even when NULL is stored here and you safe a conditional.
Disregard this. As Zi Yan mentioned in other reply, we need to keep the check and take a css reference along with transfering the memcg.
-- Michal Hocko SUSE Labs
| |