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SubjectRe: [PATCH v20 00/20] per memcg lru lock
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Hi Johannes & all,

Thanks for all comments and suggestions, here is a patch base on v20, as a summary for all you suggested:
Is this ok?

Many thanks!
Alex

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0c97292834fa..0fe4172c8c14 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -20,6 +20,9 @@
* Lockless page tracking & accounting
* Unified hierarchy configuration model
* Copyright (C) 2015 Red Hat, Inc., Johannes Weiner
+ *
+ * Per memcg lru locking
+ * Copyright (C) 2020 Alibaba, Inc, Alex Shi
*/

#include <linux/page_counter.h>
@@ -1380,6 +1383,14 @@ struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct pglist_data *pgd
return lruvec;
}

+/**
+ * lock_page_lruvec - return lruvec for the locked page.
+ * @page: the page
+ *
+ * This series functions should be used in either conditions:
+ * PageLRU is cleared or unset
+ * or, page->_refcount is zero
+ */
struct lruvec *lock_page_lruvec(struct page *page)
{
struct lruvec *lruvec;
diff --git a/mm/swap.c b/mm/swap.c
index 9fe5ff9a8111..bcc814de35c4 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -264,6 +264,13 @@ void lru_note_cost(struct lruvec *lruvec, bool file, unsigned int nr_pages)
do {
unsigned long lrusize;

+ /*
+ * Hold lruvec->lru_lock is safe here, since
+ * 1) The pinned lruvec in reclaim, or
+ * 2) From a pre-LRU page during refault (which also holds the
+ * rcu lock, so would be safe even if the page was on the LRU
+ * and could move simultaneously to a new lruvec).
+ */
spin_lock_irq(&lruvec->lru_lock);
/* Record cost event */
if (file)
@@ -355,10 +362,12 @@ static void activate_page(struct page *page)
struct lruvec *lruvec;

page = compound_head(page);
- lruvec = lock_page_lruvec_irq(page);
- if (PageLRU(page))
+ if (TestClearPageLRU(page)) {
+ lruvec = lock_page_lruvec_irq(page);
__activate_page(page, lruvec);
- unlock_page_lruvec_irq(lruvec);
+ unlock_page_lruvec_irq(lruvec);
+ SetPageLRU(page);
+ }
}
#endif

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7ed10ade548d..af03a7f2e1b8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1868,6 +1868,10 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
continue;
}

+ /*
+ * All pages were isolated from the same lruvec (and isolation
+ * inhibits memcg migration).
+ */
VM_BUG_ON_PAGE(!lruvec_holds_page_lru_lock(page, lruvec), page);
lru = page_lru(page);
nr_pages = thp_nr_pages(page);
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