linux-kernel - [RFC LPC2025 PATCH 1/4] mm/khugepaged: Remove hpage_collapse_scan

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Message-ID: <20251205233217.3344186-2-joshua.hahnjy@gmail.com>
Date: Fri,  5 Dec 2025 15:32:12 -0800
From: Joshua Hahn <joshua.hahnjy@...il.com>
To: 
Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	Barry Song <baohua@...nel.org>,
	David Hildenbrand <david@...nel.org>,
	Dev Jain <dev.jain@....com>,
	Lance Yang <lance.yang@...ux.dev>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Nico Pache <npache@...hat.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Zi Yan <ziy@...dia.com>,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-trace-kernel@...r.kernel.org
Subject: [RFC LPC2025 PATCH 1/4] mm/khugepaged: Remove hpage_collapse_scan_abort

Commit 14a4e2141e24 ("mm, thp: only collapse hugepages to nodes with
affinity for zone_reclaim_mode") introduced khugepaged_scan_abort,
which was later renamed to hpage_collapse_scan_abort. It prevents
collapsing hugepages to remote nodes when zone_reclaim_mode is enabled
as to prefer reclaiming & allocating locally instead of allocating on a
far away remote node (distance > RECLAIM_DISTANCE).

With the zone_reclaim_mode sysctl being deprecated later in the series,
remove hpage_collapse_scan_abort, its callers, and its associated values
in the scan_result enum.

Signed-off-by: Joshua Hahn <joshua.hahnjy@...il.com>
---
 include/trace/events/huge_memory.h |  1 -
 mm/khugepaged.c                    | 34 ------------------------------
 2 files changed, 35 deletions(-)

diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
index 4cde53b45a85..1c0b146d1286 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -20,7 +20,6 @@
 	EM( SCAN_PTE_MAPPED_HUGEPAGE,	"pte_mapped_hugepage")		\
 	EM( SCAN_LACK_REFERENCED_PAGE,	"lack_referenced_page")		\
 	EM( SCAN_PAGE_NULL,		"page_null")			\
-	EM( SCAN_SCAN_ABORT,		"scan_aborted")			\
 	EM( SCAN_PAGE_COUNT,		"not_suitable_page_count")	\
 	EM( SCAN_PAGE_LRU,		"page_not_in_lru")		\
 	EM( SCAN_PAGE_LOCK,		"page_locked")			\
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 97d1b2824386..a93228a53ee4 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -40,7 +40,6 @@ enum scan_result {
 	SCAN_PTE_MAPPED_HUGEPAGE,
 	SCAN_LACK_REFERENCED_PAGE,
 	SCAN_PAGE_NULL,
-	SCAN_SCAN_ABORT,
 	SCAN_PAGE_COUNT,
 	SCAN_PAGE_LRU,
 	SCAN_PAGE_LOCK,
@@ -830,30 +829,6 @@ struct collapse_control khugepaged_collapse_control = {
 	.is_khugepaged = true,
 };
 
-static bool hpage_collapse_scan_abort(int nid, struct collapse_control *cc)
-{
-	int i;
-
-	/*
-	 * If node_reclaim_mode is disabled, then no extra effort is made to
-	 * allocate memory locally.
-	 */
-	if (!node_reclaim_enabled())
-		return false;
-
-	/* If there is a count for this node already, it must be acceptable */
-	if (cc->node_load[nid])
-		return false;
-
-	for (i = 0; i < MAX_NUMNODES; i++) {
-		if (!cc->node_load[i])
-			continue;
-		if (node_distance(nid, i) > node_reclaim_distance)
-			return true;
-	}
-	return false;
-}
-
 #define khugepaged_defrag()					\
 	(transparent_hugepage_flags &				\
 	 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG))
@@ -1355,10 +1330,6 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
 		 * hit record.
 		 */
 		node = folio_nid(folio);
-		if (hpage_collapse_scan_abort(node, cc)) {
-			result = SCAN_SCAN_ABORT;
-			goto out_unmap;
-		}
 		cc->node_load[node]++;
 		if (!folio_test_lru(folio)) {
 			result = SCAN_PAGE_LRU;
@@ -2342,11 +2313,6 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
 		}
 
 		node = folio_nid(folio);
-		if (hpage_collapse_scan_abort(node, cc)) {
-			result = SCAN_SCAN_ABORT;
-			folio_put(folio);
-			break;
-		}
 		cc->node_load[node]++;
 
 		if (!folio_test_lru(folio)) {
-- 
2.47.3