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[180/212] mm/vmscan: never demote for memcg reclaim

Message ID 20210902215930.MtR2KoOu5%akpm@linux-foundation.org (mailing list archive)
State New
Headers show
Series [001/212] ia64: fix typo in a comment | expand

Commit Message

Andrew Morton Sept. 2, 2021, 9:59 p.m. UTC 
From: Dave Hansen <dave.hansen@linux.intel.com>
Subject: mm/vmscan: never demote for memcg reclaim

Global reclaim aims to reduce the amount of memory used on a given node or
set of nodes.  Migrating pages to another node serves this purpose.

memcg reclaim is different.  Its goal is to reduce the total memory
consumption of the entire memcg, across all nodes.  Migration does not
assist memcg reclaim because it just moves page contents between nodes
rather than actually reducing memory consumption.

Link: https://lkml.kernel.org/r/20210715055145.195411-9-ying.huang@intel.com
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Suggested-by: Yang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Keith Busch <kbusch@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
diff mbox series

Patch

--- a/mm/vmscan.c~mm-vmscan-never-demote-for-memcg-reclaim
+++ a/mm/vmscan.c
@@ -524,8 +524,13 @@  static long add_nr_deferred(long nr, str
 
 static bool can_demote(int nid, struct scan_control *sc)
 {
-	if (sc && sc->no_demotion)
-		return false;
+	if (sc) {
+		if (sc->no_demotion)
+			return false;
+		/* It is pointless to do demotion in memcg reclaim */
+		if (cgroup_reclaim(sc))
+			return false;
+	}
 	if (next_demotion_node(nid) == NUMA_NO_NODE)
 		return false;