linux-kernel - [patch 1/2] mm, compaction: kcompactd should not ignore pageblock skip

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Message-ID: <alpine.DEB.2.10.1708151638550.106658@chino.kir.corp.google.com>
Date:   Tue, 15 Aug 2017 16:39:30 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [patch 1/2] mm, compaction: kcompactd should not ignore pageblock
 skip

Kcompactd is needlessly ignoring pageblock skip information.  It is doing
MIGRATE_SYNC_LIGHT compaction, which is no more powerful than
MIGRATE_SYNC compaction.

If compaction recently failed to isolate memory from a set of pageblocks,
there is nothing to indicate that kcompactd will be able to do so, or
that it is beneficial from attempting to isolate memory.

Use the pageblock skip hint to avoid rescanning pageblocks needlessly
until that information is reset.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 mm/compaction.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1927,9 +1927,8 @@ static void kcompactd_do_work(pg_data_t *pgdat)
 		.total_free_scanned = 0,
 		.classzone_idx = pgdat->kcompactd_classzone_idx,
 		.mode = MIGRATE_SYNC_LIGHT,
-		.ignore_skip_hint = true,
+		.ignore_skip_hint = false,
 		.gfp_mask = GFP_KERNEL,
-
 	};
 	trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
 							cc.classzone_idx);