Re: [PATCH] mm/memcontrol: update lruvec counters in mem_cgroup_move_account

Konstantin Khlebnikov
2019-10-15T08:44:28Z

On 15/10/2019 11.20, Michal Hocko wrote:
> On Tue 15-10-19 11:09:59, Konstantin Khlebnikov wrote:
>> Mapped, dirty and writeback pages are also counted in per-lruvec stats.
>> These counters needs update when page is moved between cgroups.
>
> Please describe the user visible effect.

Surprisingly I don't see any users at this moment.
So, there is no effect in mainline kernel.

>> Fixes: 00f3ca2c2d66 ("mm: memcontrol: per-lruvec stats infrastructure")
>> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
>
> We want Cc: stable I suspect because broken stats might be really
> misleading.
>
> The patch looks ok to me otherwise
> Acked-by: Michal Hocko <mhocko@suse.com>
>
>> ---
>> mm/memcontrol.c | 18 ++++++++++++------
>> 1 file changed, 12 insertions(+), 6 deletions(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index bdac56009a38..363106578876 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -5420,6 +5420,8 @@ static int mem_cgroup_move_account(struct page *page,
>> struct mem_cgroup *from,
>> struct mem_cgroup *to)
>> {
>> + struct lruvec *from_vec, *to_vec;
>> + struct pglist_data *pgdat;
>> unsigned long flags;
>> unsigned int nr_pages = compound ? hpage_nr_pages(page) : 1;
>> int ret;
>> @@ -5443,11 +5445,15 @@ static int mem_cgroup_move_account(struct page *page,
>>
>> anon = PageAnon(page);
>>
>> + pgdat = page_pgdat(page);
>> + from_vec = mem_cgroup_lruvec(pgdat, from);
>> + to_vec = mem_cgroup_lruvec(pgdat, to);
>> +
>> spin_lock_irqsave(&from->move_lock, flags);
>>
>> if (!anon && page_mapped(page)) {
>> - __mod_memcg_state(from, NR_FILE_MAPPED, -nr_pages);
>> - __mod_memcg_state(to, NR_FILE_MAPPED, nr_pages);
>> + __mod_lruvec_state(from_vec, NR_FILE_MAPPED, -nr_pages);
>> + __mod_lruvec_state(to_vec, NR_FILE_MAPPED, nr_pages);
>> }
>>
>> /*
>> @@ -5459,14 +5465,14 @@ static int mem_cgroup_move_account(struct page *page,
>> struct address_space *mapping = page_mapping(page);
>>
>> if (mapping_cap_account_dirty(mapping)) {
>> - __mod_memcg_state(from, NR_FILE_DIRTY, -nr_pages);
>> - __mod_memcg_state(to, NR_FILE_DIRTY, nr_pages);
>> + __mod_lruvec_state(from_vec, NR_FILE_DIRTY, -nr_pages);
>> + __mod_lruvec_state(to_vec, NR_FILE_DIRTY, nr_pages);
>> }
>> }
>>
>> if (PageWriteback(page)) {
>> - __mod_memcg_state(from, NR_WRITEBACK, -nr_pages);
>> - __mod_memcg_state(to, NR_WRITEBACK, nr_pages);
>> + __mod_lruvec_state(from_vec, NR_WRITEBACK, -nr_pages);
>> + __mod_lruvec_state(to_vec, NR_WRITEBACK, nr_pages);
>> }
>>
>> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>