linux-kernel - [PATCHv2 2/8] khugepaged: Do not stop collapse if less than half PTEs are referenced

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: <20200403112928.19742-3-kirill.shutemov@linux.intel.com>
Date:   Fri,  3 Apr 2020 14:29:22 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     akpm@...ux-foundation.org, Andrea Arcangeli <aarcange@...hat.com>
Cc:     Zi Yan <ziy@...dia.com>, Yang Shi <yang.shi@...ux.alibaba.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv2 2/8] khugepaged: Do not stop collapse if less than half PTEs are referenced

__collapse_huge_page_swapin() check number of referenced PTE to decide
if the memory range is hot enough to justify swapin.

The problem is that it stops collapse altogether if there's not enough
referenced pages, not only swappingin.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Fixes: 0db501f7a34c ("mm, thp: convert from optimistic swapin collapsing to conservative")
Reviewed-by: Zi Yan <ziy@...dia.com>
---
 mm/khugepaged.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 99bab7e4d05b..14d7afc90786 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -905,7 +905,8 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
 	/* we only decide to swapin, if there is enough young ptes */
 	if (referenced < HPAGE_PMD_NR/2) {
 		trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
-		return false;
+		/* Do not block collapse, only skip swapping in */
+		return true;
 	}
 	vmf.pte = pte_offset_map(pmd, address);
 	for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE;
-- 
2.26.0