linux-kernel - [PATCH v6 09/12] khugepaged: avoid unnecessary mTHP collapse attempts

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250515030312.125567-10-npache@redhat.com>
Date: Wed, 14 May 2025 21:03:09 -0600
From: Nico Pache <npache@...hat.com>
To: linux-mm@...ck.org,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Cc: david@...hat.com,
	ziy@...dia.com,
	baolin.wang@...ux.alibaba.com,
	lorenzo.stoakes@...cle.com,
	Liam.Howlett@...cle.com,
	ryan.roberts@....com,
	dev.jain@....com,
	corbet@....net,
	rostedt@...dmis.org,
	mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com,
	akpm@...ux-foundation.org,
	baohua@...nel.org,
	willy@...radead.org,
	peterx@...hat.com,
	wangkefeng.wang@...wei.com,
	usamaarif642@...il.com,
	sunnanyong@...wei.com,
	vishal.moola@...il.com,
	thomas.hellstrom@...ux.intel.com,
	yang@...amperecomputing.com,
	kirill.shutemov@...ux.intel.com,
	aarcange@...hat.com,
	raquini@...hat.com,
	anshuman.khandual@....com,
	catalin.marinas@....com,
	tiwai@...e.de,
	will@...nel.org,
	dave.hansen@...ux.intel.com,
	jack@...e.cz,
	cl@...two.org,
	jglisse@...gle.com,
	surenb@...gle.com,
	zokeefe@...gle.com,
	hannes@...xchg.org,
	rientjes@...gle.com,
	mhocko@...e.com,
	rdunlap@...radead.org
Subject: [PATCH v6 09/12] khugepaged: avoid unnecessary mTHP collapse attempts

There are cases where, if an attempted collapse fails, all subsequent
orders are guaranteed to also fail. Avoid these collapse attempts by
bailing out early.

Signed-off-by: Nico Pache <npache@...hat.com>
---
 mm/khugepaged.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 5920d4715a11..517cf2b271d7 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1371,6 +1371,23 @@ static int khugepaged_scan_bitmap(struct mm_struct *mm, unsigned long address,
 				collapsed += (1 << order);
 				continue;
 			}
+			/*
+			 * Some ret values indicate all lower order will also
+			 * fail, dont trying to collapse smaller orders
+			 */
+			if (ret == SCAN_EXCEED_NONE_PTE ||
+				ret == SCAN_EXCEED_SWAP_PTE ||
+				ret == SCAN_EXCEED_SHARED_PTE ||
+				ret == SCAN_PTE_NON_PRESENT ||
+				ret == SCAN_PTE_UFFD_WP ||
+				ret == SCAN_ALLOC_HUGE_PAGE_FAIL ||
+				ret == SCAN_CGROUP_CHARGE_FAIL ||
+				ret == SCAN_COPY_MC ||
+				ret == SCAN_PAGE_LOCK ||
+				ret == SCAN_PAGE_COUNT)
+				goto next;
+			else
+				break;
 		}
 
 next:
-- 
2.49.0