From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay3.corp.sgi.com [198.149.34.15]) by oss.sgi.com (Postfix) with ESMTP id 1A6AF7F50 for ; Mon, 23 Mar 2015 07:24:09 -0500 (CDT) Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by relay3.corp.sgi.com (Postfix) with ESMTP id 8F2FBAC002 for ; Mon, 23 Mar 2015 05:24:08 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by cuda.sgi.com with ESMTP id NsfjN5Ez6Ful2IUz (version=TLSv1 cipher=AES256-SHA bits=256 verify=NO) for ; Mon, 23 Mar 2015 05:24:06 -0700 (PDT) From: Mel Gorman Subject: [PATCH 1/3] mm: numa: Group related processes based on VMA flags instead of page table flags Date: Mon, 23 Mar 2015 12:24:01 +0000 Message-Id: <1427113443-20973-2-git-send-email-mgorman@suse.de> In-Reply-To: <1427113443-20973-1-git-send-email-mgorman@suse.de> References: <1427113443-20973-1-git-send-email-mgorman@suse.de> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Dave Chinner Cc: linuxppc-dev@lists.ozlabs.org, Linux Kernel Mailing List , xfs@oss.sgi.com, Linux-MM , Aneesh Kumar , Andrew Morton , Linus Torvalds , Ingo Molnar , Mel Gorman Threads that share writable data within pages are grouped together as related tasks. This decision is based on whether the PTE is marked dirty which is subject to timing races between the PTE scanner update and when the application writes the page. If the page is file-backed, then background flushes and sync also affect placement. This is unpredictable behaviour which is impossible to reason about so this patch makes grouping decisions based on the VMA flags. Signed-off-by: Mel Gorman --- mm/huge_memory.c | 13 ++----------- mm/memory.c | 19 +++++++++++-------- 2 files changed, 13 insertions(+), 19 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 626e93db28ba..2f12e9fcf1a2 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1291,17 +1291,8 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, flags |= TNF_FAULT_LOCAL; } - /* - * Avoid grouping on DSO/COW pages in specific and RO pages - * in general, RO pages shouldn't hurt as much anyway since - * they can be in shared cache state. - * - * FIXME! This checks "pmd_dirty()" as an approximation of - * "is this a read-only page", since checking "pmd_write()" - * is even more broken. We haven't actually turned this into - * a writable page, so pmd_write() will always be false. - */ - if (!pmd_dirty(pmd)) + /* See similar comment in do_numa_page for explanation */ + if (!(vma->vm_flags & VM_WRITE)) flags |= TNF_NO_GROUP; /* diff --git a/mm/memory.c b/mm/memory.c index 411144f977b1..20beb6647dba 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3069,16 +3069,19 @@ static int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, } /* - * Avoid grouping on DSO/COW pages in specific and RO pages - * in general, RO pages shouldn't hurt as much anyway since - * they can be in shared cache state. + * Avoid grouping on RO pages in general. RO pages shouldn't hurt as + * much anyway since they can be in shared cache state. This misses + * the case where a mapping is writable but the process never writes + * to it but pte_write gets cleared during protection updates and + * pte_dirty has unpredictable behaviour between PTE scan updates, + * background writeback, dirty balancing and application behaviour. * - * FIXME! This checks "pmd_dirty()" as an approximation of - * "is this a read-only page", since checking "pmd_write()" - * is even more broken. We haven't actually turned this into - * a writable page, so pmd_write() will always be false. + * TODO: Note that the ideal here would be to avoid a situation where a + * NUMA fault is taken immediately followed by a write fault in + * some cases which would have lower overhead overall but would be + * invasive as the fault paths would need to be unified. */ - if (!pte_dirty(pte)) + if (!(vma->vm_flags & VM_WRITE)) flags |= TNF_NO_GROUP; /* -- 2.1.2 _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs