From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f177.google.com (mail-pf0-f177.google.com [209.85.192.177]) by kanga.kvack.org (Postfix) with ESMTP id 994496B0005 for ; Mon, 11 Apr 2016 02:10:57 -0400 (EDT) Received: by mail-pf0-f177.google.com with SMTP id c20so117579853pfc.1 for ; Sun, 10 Apr 2016 23:10:57 -0700 (PDT) Received: from e28smtp09.in.ibm.com (e28smtp09.in.ibm.com. [125.16.236.9]) by mx.google.com with ESMTPS id c62si1480453pfd.69.2016.04.10.23.10.56 for (version=TLS1_2 cipher=AES128-SHA bits=128/128); Sun, 10 Apr 2016 23:10:56 -0700 (PDT) Received: from localhost by e28smtp09.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 11 Apr 2016 11:40:54 +0530 Received: from d28av02.in.ibm.com (d28av02.in.ibm.com [9.184.220.64]) by d28relay03.in.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u3B6AlnV6095162 for ; Mon, 11 Apr 2016 11:40:47 +0530 Received: from d28av02.in.ibm.com (localhost [127.0.0.1]) by d28av02.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u3B6AhsW009363 for ; Mon, 11 Apr 2016 11:40:45 +0530 Message-ID: <570B3FDB.90305@linux.vnet.ibm.com> Date: Mon, 11 Apr 2016 11:40:35 +0530 From: Anshuman Khandual MIME-Version: 1.0 Subject: Re: [PATCH 02/10] mm/hugetlb: Add PGD based implementation awareness References: <1460007464-26726-1-git-send-email-khandual@linux.vnet.ibm.com> <1460007464-26726-3-git-send-email-khandual@linux.vnet.ibm.com> <570622B4.5020407@gmail.com> <570B3531.2000808@linux.vnet.ibm.com> In-Reply-To: <570B3531.2000808@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Balbir Singh , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Cc: hughd@google.com, dave.hansen@intel.com, aneesh.kumar@linux.vnet.ibm.com, kirill@shutemov.name, n-horiguchi@ah.jp.nec.com, mgorman@techsingularity.net, akpm@linux-foundation.org On 04/11/2016 10:55 AM, Anshuman Khandual wrote: > On 04/07/2016 02:34 PM, Balbir Singh wrote: >> > >> > >> > On 07/04/16 15:37, Anshuman Khandual wrote: >>> >> Currently the config ARCH_WANT_GENERAL_HUGETLB enabled functions like >>> >> 'huge_pte_alloc' and 'huge_pte_offset' dont take into account HugeTLB >>> >> page implementation at the PGD level. This is also true for functions >>> >> like 'follow_page_mask' which is called from move_pages() system call. >>> >> This lack of PGD level huge page support prohibits some architectures >>> >> to use these generic HugeTLB functions. >>> >> >> > >> > From what I know of move_pages(), it will always call follow_page_mask() >> > with FOLL_GET (I could be wrong here) and the implementation below >> > returns NULL for follow_huge_pgd(). > You are right. This patch makes ARCH_WANT_GENERAL_HUGETLB functions aware > of PGD implementation so that we can do all transactions on 16GB pages > using these function instead of the present arch overrides. But that also > requires follow_page_mask() changes for every other access to the page > than the migrate_pages() usage. > > But yes, we dont support migrate_pages() on PGD based pages yet, hence > it just returns NULL in that case. May be the commit message needs to > reflect this. The next commit actually changes follow_huge_pud|pgd() functions to support FOLL_GET and PGD based huge page migration. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org