Re: [PATCH 5/5] mm: page_alloc: defrag_mode kswapd/kcompactd watermarks

[Johannes Weiner <hannes@cmpxchg.org>]

Andrew, could you please fold this delta patch?

---

From 3d2ff7b72df9e4f1a31b3cff2ae6a4584c06bdca Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Fri, 14 Mar 2025 11:38:41 -0400
Subject: [PATCH] mm: page_alloc: defrag_mode kswapd/kcompactd watermarks fix

Fix squawks from rebasing that affect the behavior of !defrag_mode.

FWIW, it seems to actually have slightly helped the vanilla kernel in
the benchmark. But the point was to not change the default behavior:

                                                VANILLA        WMARKFIX-VANILLA
Hugealloc Time mean               52739.45 (    +0.00%)   62758.21 (   +19.00%)
Hugealloc Time stddev             56541.26 (    +0.00%)   76253.41 (   +34.86%)
Kbuild Real time                    197.47 (    +0.00%)     197.25 (    -0.11%)
Kbuild User time                   1240.49 (    +0.00%)    1241.33 (    +0.07%)
Kbuild System time                   70.08 (    +0.00%)      71.00 (    +1.28%)
THP fault alloc                   46727.07 (    +0.00%)   41492.73 (   -11.20%)
THP fault fallback                21910.60 (    +0.00%)   27146.53 (   +23.90%)
Direct compact fail                 195.80 (    +0.00%)     260.93 (   +33.10%)
Direct compact success                7.93 (    +0.00%)       6.67 (   -14.18%)
Direct compact success rate %         3.51 (    +0.00%)       2.76 (   -16.78%)
Compact daemon scanned migrate  3369601.27 (    +0.00%) 3827734.27 (   +13.60%)
Compact daemon scanned free     5075474.47 (    +0.00%) 5910839.73 (   +16.46%)
Compact direct scanned migrate   161787.27 (    +0.00%)  168271.13 (    +4.01%)
Compact direct scanned free      163467.53 (    +0.00%)  222558.33 (   +36.15%)
Compact total migrate scanned   3531388.53 (    +0.00%) 3996005.40 (   +13.16%)
Compact total free scanned      5238942.00 (    +0.00%) 6133398.07 (   +17.07%)
Alloc stall                        2371.07 (    +0.00%)    2478.00 (    +4.51%)
Pages kswapd scanned            2160926.73 (    +0.00%) 1726204.67 (   -20.12%)
Pages kswapd reclaimed           533191.07 (    +0.00%)  537963.73 (    +0.90%)
Pages direct scanned             400450.33 (    +0.00%)  450004.87 (   +12.37%)
Pages direct reclaimed            94441.73 (    +0.00%)   99193.07 (    +5.03%)
Pages total scanned             2561377.07 (    +0.00%) 2176209.53 (   -15.04%)
Pages total reclaimed            627632.80 (    +0.00%)  637156.80 (    +1.52%)
Swap out                          47959.53 (    +0.00%)   45186.20 (    -5.78%)
Swap in                            7276.00 (    +0.00%)    7109.40 (    -2.29%)
File refaults                    138043.00 (    +0.00%)  145238.73 (    +5.21%)

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/compaction.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 4a2ccb82d0b2..a481755791a9 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -3075,6 +3075,8 @@ static bool kcompactd_node_suitable(pg_data_t *pgdat)
 	struct zone *zone;
 	enum zone_type highest_zoneidx = pgdat->kcompactd_highest_zoneidx;
 	enum compact_result ret;
+	unsigned int alloc_flags = defrag_mode ?
+		ALLOC_WMARK_HIGH : ALLOC_WMARK_MIN;
 
 	for (zoneid = 0; zoneid <= highest_zoneidx; zoneid++) {
 		zone = &pgdat->node_zones[zoneid];
@@ -3084,7 +3086,7 @@ static bool kcompactd_node_suitable(pg_data_t *pgdat)
 
 		ret = compaction_suit_allocation_order(zone,
 				pgdat->kcompactd_max_order,
-				highest_zoneidx, ALLOC_WMARK_MIN,
+				highest_zoneidx, alloc_flags,
 				false, true);
 		if (ret == COMPACT_CONTINUE)
 			return true;
@@ -3108,7 +3110,7 @@ static void kcompactd_do_work(pg_data_t *pgdat)
 		.mode = MIGRATE_SYNC_LIGHT,
 		.ignore_skip_hint = false,
 		.gfp_mask = GFP_KERNEL,
-		.alloc_flags = ALLOC_WMARK_HIGH,
+		.alloc_flags = defrag_mode ? ALLOC_WMARK_HIGH : ALLOC_WMARK_MIN,
 	};
 	enum compact_result ret;
 
-- 
2.48.1