From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753358AbaJBN33 (ORCPT ); Thu, 2 Oct 2014 09:29:29 -0400 Received: from cantor2.suse.de ([195.135.220.15]:35434 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752480AbaJBN31 (ORCPT ); Thu, 2 Oct 2014 09:29:27 -0400 From: Mel Gorman To: Dave Jones Cc: Linus Torvalds , Hugh Dickins , Al Viro , Rik van Riel , Ingo Molnar , Peter Zijlstra , Aneesh Kumar , Michel Lespinasse , Kirill A Shutemov , Mel Gorman , Linux Kernel Subject: [PATCH 4/4] mm: numa: Do not mark PTEs pte_numa when splitting huge pages Date: Thu, 2 Oct 2014 14:29:18 +0100 Message-Id: <1412256558-9995-5-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 1.8.4.5 In-Reply-To: <1412256558-9995-1-git-send-email-mgorman@suse.de> References: <1412256558-9995-1-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch reverts 1ba6e0b50b ("mm: numa: split_huge_page: transfer the NUMA type from the pmd to the pte"). If a huge page is being split due a protection change and the tail will be in a PROT_NONE vma then NUMA hinting PTEs are temporarily created in the protected VMA. VM_RW|VM_PROTNONE |-----------------| ^ split here In the specific case above, it should get fixed up by change_pte_range() but there is a window of opportunity for weirdness to happen. Similarly, if a huge page is shrunk and split during a protection update but before pmd_numa is cleared then a pte_numa can be left behind. Instead of adding complexity trying to deal with the case, this patch will not mark PTEs NUMA when splitting a huge page. NUMA hinting faults will not be triggered which is marginal in comparison to the complexity in dealing with the corner cases during THP split. Signed-off-by: Mel Gorman --- mm/huge_memory.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index d9a21d06..17a74d6 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1801,8 +1801,6 @@ static int __split_huge_page_map(struct page *page, entry = pte_wrprotect(entry); if (!pmd_young(*pmd)) entry = pte_mkold(entry); - if (pmd_numa(*pmd)) - entry = pte_mknuma(entry); pte = pte_offset_map(&_pmd, haddr); BUG_ON(!pte_none(*pte)); set_pte_at(mm, haddr, pte, entry); -- 1.8.4.5