linux-kernel - [PATCH v1 7/7] mm/mlock: recharge mlocked pages at culling by vmscan

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Date:   Wed, 04 Sep 2019 16:53:22 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org
Cc:     Michal Hocko <mhocko@...e.com>, Roman Gushchin <guro@...com>,
        Johannes Weiner <hannes@...xchg.org>
Subject: [PATCH v1 7/7] mm/mlock: recharge mlocked pages at culling by vmscan

If mlock cannot catch page in LRU then it isn't moved into unevictable lru.
These pages are 'culled' by reclaimer and moved into unevictable lru.
It seems pages locked with MLOCK_ONFAULT always go through this path.

Reclaimer calls try_to_unmap for already isolated pages, thus on this path
we could freely change page to owner of any mlock vma we found in rmap.

This patch passes flag TTU_LRU_ISOLATED into try_to_ummap to move pages
in mmlock_vma_page().

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
---
 mm/vmscan.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index bf7a05e8a717..2060f254dd6b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1345,7 +1345,8 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		 * processes. Try to unmap it here.
 		 */
 		if (page_mapped(page)) {
-			enum ttu_flags flags = ttu_flags | TTU_BATCH_FLUSH;
+			enum ttu_flags flags = ttu_flags | TTU_BATCH_FLUSH |
+					       TTU_LRU_ISOLATED;

 			if (unlikely(PageTransHuge(page)))
 				flags |= TTU_SPLIT_HUGE_PMD;