On 25/12/2019 12.04, Alex Shi wrote:
From the commit_charge's explanations and mem_cgroup_commit_charge
comments, as well as call path when lrucare is ture, The lru_lock is
just to guard the task migration(which would be lead to move_account)
So it isn't needed when !PageLRU, and better be fold into PageLRU to
reduce lock contentions.
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: cgroups@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
mm/memcontrol.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c5b5f74cfd4d..0ad10caabc3d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2572,12 +2572,11 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
static void lock_page_lru(struct page *page, int *isolated)
{
- pg_data_t *pgdat = page_pgdat(page);
-
- spin_lock_irq(&pgdat->lru_lock);
if (PageLRU(page)) {
+ pg_data_t *pgdat = page_pgdat(page);
struct lruvec *lruvec;
+ spin_lock_irq(&pgdat->lru_lock);
That's wrong. Here PageLRU must be checked again under lru_lock.
Also I don't like these functions:
- called lock/unlock but actually also isolates
- used just once
- pgdat evaluated twice
lruvec = mem_cgroup_page_lruvec(page, pgdat);
ClearPageLRU(page);
del_page_from_lru_list(page, lruvec, page_lru(page));
@@ -2588,17 +2587,17 @@ static void lock_page_lru(struct page *page, int *isolated)
static void unlock_page_lru(struct page *page, int isolated)
{
- pg_data_t *pgdat = page_pgdat(page);
if (isolated) {
+ pg_data_t *pgdat = page_pgdat(page);
struct lruvec *lruvec;
lruvec = mem_cgroup_page_lruvec(page, pgdat);
VM_BUG_ON_PAGE(PageLRU(page), page);
SetPageLRU(page);
add_page_to_lru_list(page, lruvec, page_lru(page));
+ spin_unlock_irq(&pgdat->lru_lock);
}
- spin_unlock_irq(&pgdat->lru_lock);
}
static void commit_charge(struct page *page, struct mem_cgroup *memcg,
