Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932941Ab3GOPYg (ORCPT ); Mon, 15 Jul 2013 11:24:36 -0400 Received: from cantor2.suse.de ([195.135.220.15]:46085 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932507Ab3GOPU1 (ORCPT ); Mon, 15 Jul 2013 11:20:27 -0400 From: Mel Gorman To: Peter Zijlstra , Srikar Dronamraju Cc: Ingo Molnar , Andrea Arcangeli , Johannes Weiner , Linux-MM , LKML , Mel Gorman Subject: [PATCH 04/18] mm: numa: Do not migrate or account for hinting faults on the zero page Date: Mon, 15 Jul 2013 16:20:06 +0100 Message-Id: <1373901620-2021-5-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1373901620-2021-1-git-send-email-mgorman@suse.de> References: <1373901620-2021-1-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2092 Lines: 60 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 --- 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..6c6f6b0 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 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/