mm: vmscan: memcontrol: remove mem_cgroup_select_victim_node()

Since commit 1ba6fc9af35b ("mm: vmscan: do not share cgroup iteration
between reclaimers"), the memcg reclaim does not bail out earlier based
on sc->nr_reclaimed and will traverse all the nodes.  All the
reclaimable pages of the memcg on all the nodes will be scanned relative
to the reclaim priority.  So, there is no need to maintain state
regarding which node to start the memcg reclaim from.

This patch effectively reverts the commit 889976dbcb12 ("memcg: reclaim
memory from nodes in round-robin order") and commit 453a9bf347f1
("memcg: fix numa scan information update to be triggered by memory
event").

[shakeelb@google.com: v2]
  Link: http://lkml.kernel.org/r/20191030204232.139424-1-shakeelb@google.com
Link: http://lkml.kernel.org/r/20191029234753.224143-1-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 9 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ee4eecc7e1c2..2beff0e0dc7b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3348,10 +3348,8 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 					   gfp_t gfp_mask,
 					   bool may_swap)
 {
-	struct zonelist *zonelist;
 	unsigned long nr_reclaimed;
 	unsigned long pflags;
-	int nid;
 	unsigned int noreclaim_flag;
 	struct scan_control sc = {
 		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
@@ -3364,16 +3362,14 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 		.may_unmap = 1,
 		.may_swap = may_swap,
 	};
-
-	set_task_reclaim_state(current, &sc.reclaim_state);
 	/*
-	 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
-	 * take care of from where we get pages. So the node where we start the
-	 * scan does not need to be the current node.
+	 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
+	 * equal pressure on all the nodes. This is based on the assumption that
+	 * the reclaim does not bail out early.
 	 */
-	nid = mem_cgroup_select_victim_node(memcg);
+	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
 
-	zonelist = &NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK];
+	set_task_reclaim_state(current, &sc.reclaim_state);
 
 	trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);