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Subject[PATCH 2/4] mm: Fix memcg stack accounting for sub-page stacks
Date
We should account for stacks regardless of stack size, and we need
to account in sub-page units if THREAD_SIZE < PAGE_SIZE. Change the
units to kilobytes and Move it into account_kernel_stack().

Fixes: 12580e4b54ba8 ("mm: memcontrol: report kernel stack usage in cgroup2 memory.stat")
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
include/linux/memcontrol.h | 2 +-
kernel/fork.c | 19 ++++++++-----------
mm/memcontrol.c | 2 +-
3 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index a805474df4ab..3b653b86bb8f 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -52,7 +52,7 @@ enum mem_cgroup_stat_index {
MEM_CGROUP_STAT_SWAP, /* # of pages, swapped out */
MEM_CGROUP_STAT_NSTATS,
/* default hierarchy stats */
- MEMCG_KERNEL_STACK = MEM_CGROUP_STAT_NSTATS,
+ MEMCG_KERNEL_STACK_KB = MEM_CGROUP_STAT_NSTATS,
MEMCG_SLAB_RECLAIMABLE,
MEMCG_SLAB_UNRECLAIMABLE,
MEMCG_SOCK,
diff --git a/kernel/fork.c b/kernel/fork.c
index 466ba8febe3b..146c9840c079 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -165,20 +165,12 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP,
THREAD_SIZE_ORDER);

- if (page)
- memcg_kmem_update_page_stat(page, MEMCG_KERNEL_STACK,
- 1 << THREAD_SIZE_ORDER);
-
return page ? page_address(page) : NULL;
}

static inline void free_thread_stack(unsigned long *stack)
{
- struct page *page = virt_to_page(stack);
-
- memcg_kmem_update_page_stat(page, MEMCG_KERNEL_STACK,
- -(1 << THREAD_SIZE_ORDER));
- __free_kmem_pages(page, THREAD_SIZE_ORDER);
+ free_kmem_pages((unsigned long)stack, THREAD_SIZE_ORDER);
}
# else
static struct kmem_cache *thread_stack_cache;
@@ -223,10 +215,15 @@ static struct kmem_cache *mm_cachep;

static void account_kernel_stack(unsigned long *stack, int account)
{
- struct zone *zone = page_zone(virt_to_page(stack));
+ /* All stack pages are in the same zone and belong to the same memcg. */
+ struct page *first_page = virt_to_page(stack);

- mod_zone_page_state(zone, NR_KERNEL_STACK_KB,
+ mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
THREAD_SIZE / 1024 * account);
+
+ memcg_kmem_update_page_stat(
+ first_page, MEMCG_KERNEL_STACK_KB,
+ account * (THREAD_SIZE / 1024));
}

void free_task(struct task_struct *tsk)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ac8664db3823..ee44afc1f2d0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5133,7 +5133,7 @@ static int memory_stat_show(struct seq_file *m, void *v)
seq_printf(m, "file %llu\n",
(u64)stat[MEM_CGROUP_STAT_CACHE] * PAGE_SIZE);
seq_printf(m, "kernel_stack %llu\n",
- (u64)stat[MEMCG_KERNEL_STACK] * PAGE_SIZE);
+ (u64)stat[MEMCG_KERNEL_STACK_KB] * 1024);
seq_printf(m, "slab %llu\n",
(u64)(stat[MEMCG_SLAB_RECLAIMABLE] +
stat[MEMCG_SLAB_UNRECLAIMABLE]) * PAGE_SIZE);
--
2.7.4
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