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Subject[patch 07/10] mm: vmscan: convert global reclaim to per-memcg LRU lists
Date
The global per-zone LRU lists are about to go away on memcg-enabled
kernels, global reclaim must be able to find its pages on the
per-memcg LRU lists.

Since the LRU pages of a zone are distributed over all existing memory
cgroups, a scan target for a zone is complete when all memory cgroups
are scanned for their proportional share of a zone's memory.

The forced scanning of small scan targets from kswapd is limited to
zones marked unreclaimable, otherwise kswapd can quickly overreclaim
by force-scanning the LRU lists of multiple memory cgroups.

Signed-off-by: Johannes Weiner <jweiner@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Kirill A. Shutemov <kirill@shutemov.name>
---
mm/vmscan.c | 39 ++++++++++++++++++++++-----------------
1 files changed, 22 insertions(+), 17 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 96acc1a..f411e7f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1887,7 +1887,7 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
* latencies, so it's better to scan a minimum amount there as
* well.
*/
- if (current_is_kswapd())
+ if (current_is_kswapd() && mz->zone->all_unreclaimable)
force_scan = true;
if (!global_reclaim(sc))
force_scan = true;
@@ -2111,16 +2111,6 @@ static void shrink_zone(int priority, struct zone *zone,
};
struct mem_cgroup *memcg;

- if (global_reclaim(sc)) {
- struct mem_cgroup_zone mz = {
- .mem_cgroup = NULL,
- .zone = zone,
- };
-
- shrink_mem_cgroup_zone(priority, &mz, sc);
- return;
- }
-
memcg = mem_cgroup_iter(root, NULL, &reclaim);
do {
struct mem_cgroup_zone mz = {
@@ -2134,6 +2124,10 @@ static void shrink_zone(int priority, struct zone *zone,
* scanned it with decreasing priority levels until
* nr_to_reclaim had been reclaimed. This priority
* cycle is thus over after a single memcg.
+ *
+ * Direct reclaim and kswapd, on the other hand, have
+ * to scan all memory cgroups to fulfill the overall
+ * scan target for the zone.
*/
if (!global_reclaim(sc)) {
mem_cgroup_iter_break(root, memcg);
@@ -2451,13 +2445,24 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
static void age_active_anon(struct zone *zone, struct scan_control *sc,
int priority)
{
- struct mem_cgroup_zone mz = {
- .mem_cgroup = NULL,
- .zone = zone,
- };
+ struct mem_cgroup *memcg;

- if (inactive_anon_is_low(&mz))
- shrink_active_list(SWAP_CLUSTER_MAX, &mz, sc, priority, 0);
+ if (!total_swap_pages)
+ return;
+
+ memcg = mem_cgroup_iter(NULL, NULL, NULL);
+ do {
+ struct mem_cgroup_zone mz = {
+ .mem_cgroup = memcg,
+ .zone = zone,
+ };
+
+ if (inactive_anon_is_low(&mz))
+ shrink_active_list(SWAP_CLUSTER_MAX, &mz,
+ sc, priority, 0);
+
+ memcg = mem_cgroup_iter(NULL, memcg, NULL);
+ } while (memcg);
}

/*
--
1.7.6.2


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