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

From: Konstantin Khlebnikov
Date: Tue Oct 15 2019 - 06:49:24 EST


On 15/10/2019 13.36, Michal Hocko wrote:
On Tue 15-10-19 11:44:22, Konstantin Khlebnikov wrote:
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.

Those counters are exported right? Or do we exclude them for v1?

It seems per-lruvec statistics is not exposed anywhere.
And per-lruvec NR_FILE_MAPPED, NR_FILE_DIRTY, NR_WRITEBACK never had users.

I've found this because I'm using mem_cgroup_move_account for recharging
pages at mlock and playing right now with debug for memory cgroup which
validates statistics and counters when cgroup dies.


Fixes: 00f3ca2c2d66 ("mm: memcontrol: per-lruvec stats infrastructure")
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>

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@xxxxxxxx>

---
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