linux-kernel - [PATCH 04/16] mm: numa: Do not migrate or account for hinting faults on the zero page

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: <1373536020-2799-5-git-send-email-mgorman@suse.de>
Date:	Thu, 11 Jul 2013 10:46:48 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, Mel Gorman <mgorman@...e.de>
Subject: [PATCH 04/16] mm: numa: Do not migrate or account for hinting faults on the zero page

The zero page is not replicated between nodes and is often shared
between processes. The data is read-only and likely to be cached in
local CPUs if heavily accessed meaning that the remote memory access
cost is less of a concern. This patch stops accounting for numa hinting
faults on the zero page in both terms of counting faults and scheduling
tasks on nodes.

Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 mm/huge_memory.c | 9 +++++++++
 mm/memory.c      | 7 ++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e4a79fa..ec938ed 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1302,6 +1302,15 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
 
 	page = pmd_page(pmd);
 	get_page(page);
+
+	/*
+	 * Do not account for faults against the huge zero page. The read-only
+	 * data is likely to be read-cached on the local CPUs and it is less
+	 * useful to know about local versus remote hits on the zero page.
+	 */
+	if (is_huge_zero_pfn(page_to_pfn(page)))
+		goto clear_pmdnuma;
+
 	src_nid = numa_node_id();
 	count_vm_numa_event(NUMA_HINT_FAULTS);
 	if (src_nid == page_to_nid(page))
diff --git a/mm/memory.c b/mm/memory.c
index ba94dec..422351c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3560,8 +3560,13 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	set_pte_at(mm, addr, ptep, pte);
 	update_mmu_cache(vma, addr, ptep);
 
+	/*
+	 * Do not account for faults against the huge zero page. The read-only
+	 * data is likely to be read-cached on the local CPUs and it is less
+	 * useful to know about local versus remote hits on the zero page.
+	 */
 	page = vm_normal_page(vma, addr, pte);
-	if (!page) {
+	if (!page || is_zero_pfn(page_to_pfn(page))) {
 		pte_unmap_unlock(ptep, ptl);
 		return 0;
 	}
-- 
1.8.1.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/