+ mm-vmscan-never-demote-for-memcg-reclaim.patch added to -mm tree

* + mm-vmscan-never-demote-for-memcg-reclaim.patch added to -mm tree
@ 2021-07-15 21:28 akpm
  0 siblings, 0 replies; 2+ messages in thread
From: akpm @ 2021-07-15 21:28 UTC (permalink / raw)
  To: dan.j.williams, dave.hansen, david, gthelen, kbusch, mhocko,
	mm-commits, osalvador, rientjes, shy828301, weixugc, yang.shi,
	ying.huang, ziy


The patch titled
     Subject: mm/vmscan: never demote for memcg reclaim
has been added to the -mm tree.  Its filename is
     mm-vmscan-never-demote-for-memcg-reclaim.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-vmscan-never-demote-for-memcg-reclaim.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-vmscan-never-demote-for-memcg-reclaim.patch

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------------------------------------------------------
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>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Zi Yan <ziy@nvidia.com>
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(-)

--- a/mm/vmscan.c~mm-vmscan-never-demote-for-memcg-reclaim
+++ a/mm/vmscan.c
@@ -521,8 +521,13 @@ static long add_nr_deferred(long nr, str
 
 static bool can_demote_anon_pages(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;
 
_

Patches currently in -mm which might be from dave.hansen@linux.intel.com are

mm-numa-automatically-generate-node-migration-order.patch
mm-migrate-update-node-demotion-order-on-hotplug-events.patch
mm-migrate-demote-pages-during-reclaim.patch
mm-vmscan-add-helper-for-querying-ability-to-age-anonymous-pages.patch
mm-vmscan-never-demote-for-memcg-reclaim.patch
mm-mempolicy-add-mpol_preferred_many-for-multiple-preferred-nodes.patch


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