linux-kernel - [PATCH RFC] mm: do not start node_reclaim for page order > MAX

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Message-ID: <154109387197.925352.10499549042420271600.stgit@buzz>
Date:   Thu, 01 Nov 2018 20:37:52 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>, linux-kernel@...r.kernel.org
Subject: [PATCH RFC] mm: do not start node_reclaim for page order > MAX_ORDER

Page allocator has check in __alloc_pages_slowpath() but nowdays
there is earlier entry point into reclimer without such check:
get_page_from_freelist() -> node_reclaim().

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
---
 mm/vmscan.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 62ac0c488624..52f672420f0b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4117,6 +4117,12 @@ int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
 {
 	int ret;
 
+	/*
+	 * Do not scan if allocation will never succeed.
+	 */
+	if (order >= MAX_ORDER)
+		return NODE_RECLAIM_NOSCAN;
+
 	/*
 	 * Node reclaim reclaims unmapped file backed pages and
 	 * slab pages if we are over the defined limits.