在 2021/3/2 10:00, Zi Yan 写道:
> On 1 Mar 2021, at 20:34, 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.
>>
>> Signed-off-by: Zhou Guanghui <zhouguanghui1@xxxxxxxxxx>
>> ---
>> 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;
>> +}
>> +
>> struct mem_cgroup *lock_page_memcg(struct page *page);
>> void __unlock_page_memcg(struct mem_cgroup *memcg);
>> void unlock_page_memcg(struct page *page);
>> @@ -1291,6 +1297,10 @@ mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg)
>> {
>> }
>>
>> +static inline void copy_page_memcg(struct page *dst, struct page *src)
>> +{
>> +}
>> +
>> static inline struct mem_cgroup *lock_page_memcg(struct page *page)
>> {
>> return NULL;
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 3e4b29ee2b1e..ee0a63dc1c9b 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -3307,8 +3307,10 @@ void split_page(struct page *page, unsigned int order)
>> VM_BUG_ON_PAGE(PageCompound(page), page);
>> VM_BUG_ON_PAGE(!page_count(page), page);
>>
>> - for (i = 1; i < (1 << order); i++)
>> + for (i = 1; i < (1 << order); i++) {
>> set_page_refcounted(page + i);
>> + copy_page_memcg(page + i, page);
>> + }
>> split_page_owner(page, 1 << order);
>> }
>> EXPORT_SYMBOL_GPL(split_page);
>> --
>> 2.25.0
>
> +memcg maintainers
>
> split_page() is used for non-compound higher-order pages. I am not sure
> if there is any such pages monitored by memcg. Please let me know
> if I miss anything.
Thank you for taking time for this.
This should be put in kmemcg, and I'll modify it.
When the kmemcg is enabled and _GFP_ACCOUNT is set, the charged and
uncharged sizes do not match when alloc/free_pages_exact method is used
to apply for or free memory with exact size. This is because memcg data
of the tail page is not set during the split page.
