linux-kernel - [PATCH v2 5/7] mm: vmscan: do not scan anon pages if memcg swap limit is hit

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Message-ID: <6f6fa6cbfe005917911f89b2b12d5fbfa0b071e4.1450352792.git.vdavydov@virtuozzo.com>
Date:	Thu, 17 Dec 2015 15:29:58 +0300
From:	Vladimir Davydov <vdavydov@...tuozzo.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>, <linux-mm@...ck.org>,
	<cgroups@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 5/7] mm: vmscan: do not scan anon pages if memcg swap limit is hit

We don't scan anonymous memory if we ran out of swap, neither should we
do it in case memcg swap limit is hit, because swap out is impossible
anyway.

Signed-off-by: Vladimir Davydov <vdavydov@...tuozzo.com>
Acked-by: Johannes Weiner <hannes@...xchg.org>
---
Changes in v2:
 - Do not check swap limit on the legacy hierarchy.

 include/linux/swap.h |  6 ++++++
 mm/memcontrol.c      | 13 +++++++++++++
 mm/vmscan.c          |  2 +-
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index f8fb4e06c4bd..c544998dfbe7 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -551,6 +551,7 @@ static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
 extern void mem_cgroup_swapout(struct page *page, swp_entry_t entry);
 extern int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry);
 extern void mem_cgroup_uncharge_swap(swp_entry_t entry);
+extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
 #else
 static inline void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 {
@@ -565,6 +566,11 @@ static inline int mem_cgroup_try_charge_swap(struct page *page,
 static inline void mem_cgroup_uncharge_swap(swp_entry_t entry)
 {
 }
+
+static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
+{
+	return get_nr_swap_pages();
+}
 #endif
 
 #endif /* __KERNEL__*/
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 567b56da2c23..e0e498f5ca32 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5736,6 +5736,19 @@ void mem_cgroup_uncharge_swap(swp_entry_t entry)
 	rcu_read_unlock();
 }
 
+long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
+{
+	long nr_swap_pages = get_nr_swap_pages();
+
+	if (!do_swap_account || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
+		return nr_swap_pages;
+	for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg))
+		nr_swap_pages = min_t(long, nr_swap_pages,
+				      READ_ONCE(memcg->swap.limit) -
+				      page_counter_read(&memcg->swap));
+	return nr_swap_pages;
+}
+
 /* for remember boot option*/
 #ifdef CONFIG_MEMCG_SWAP_ENABLED
 static int really_do_swap_account __initdata = 1;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b220e6cda25d..ab52d865d922 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1995,7 +1995,7 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
 		force_scan = true;
 
 	/* If we have no swap space, do not bother scanning anon pages. */
-	if (!sc->may_swap || (get_nr_swap_pages() <= 0)) {
+	if (!sc->may_swap || mem_cgroup_get_nr_swap_pages(memcg) <= 0) {
 		scan_balance = SCAN_FILE;
 		goto out;
 	}
-- 
2.1.4

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