Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757500AbcCaQpo (ORCPT ); Thu, 31 Mar 2016 12:45:44 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:46878 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755652AbcCaQpm (ORCPT ); Thu, 31 Mar 2016 12:45:42 -0400 Subject: Re: [RFC PATCH 1/2] mm/hugetlbfs: Attempt PUD_SIZE mapping alignment if PMD sharing enabled To: Naoya Horiguchi References: <1459213970-17957-1-git-send-email-mike.kravetz@oracle.com> <1459213970-17957-2-git-send-email-mike.kravetz@oracle.com> <20160331021850.GA4079@hori1.linux.bs1.fc.nec.co.jp> Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "x86@kernel.org" , Hugh Dickins , Hillf Danton , "Kirill A. Shutemov" , David Rientjes , Dave Hansen , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Catalin Marinas , Will Deacon , Steve Capper , Andrew Morton From: Mike Kravetz Message-ID: <56FD541B.4040002@oracle.com> Date: Thu, 31 Mar 2016 09:45:15 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20160331021850.GA4079@hori1.linux.bs1.fc.nec.co.jp> Content-Type: text/plain; charset=iso-2022-jp Content-Transfer-Encoding: 7bit X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1770 Lines: 54 On 03/30/2016 07:18 PM, Naoya Horiguchi wrote: > On Mon, Mar 28, 2016 at 06:12:49PM -0700, Mike Kravetz wrote: >> When creating a hugetlb mapping, attempt PUD_SIZE alignment if the >> following conditions are met: >> - Address passed to mmap or shmat is NULL >> - The mapping is flaged as shared >> - The mapping is at least PUD_SIZE in length >> If a PUD_SIZE aligned mapping can not be created, then fall back to a >> huge page size mapping. > > It would be kinder if the patch description includes why this change. > Simply "to facilitate pmd sharing" is helpful for someone who read > "git log". Ok, will do. > >> >> Signed-off-by: Mike Kravetz >> --- >> fs/hugetlbfs/inode.c | 29 +++++++++++++++++++++++++++-- >> 1 file changed, 27 insertions(+), 2 deletions(-) >> >> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c >> index 540ddc9..22b2e38 100644 >> --- a/fs/hugetlbfs/inode.c >> +++ b/fs/hugetlbfs/inode.c >> @@ -175,6 +175,17 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr, >> struct vm_area_struct *vma; >> struct hstate *h = hstate_file(file); >> struct vm_unmapped_area_info info; >> + bool pud_size_align = false; >> + unsigned long ret_addr; >> + >> + /* >> + * If PMD sharing is enabled, align to PUD_SIZE to facilitate >> + * sharing. Only attempt alignment if no address was passed in, >> + * flags indicate sharing and size is big enough. >> + */ >> + if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) && >> + !addr && flags & MAP_SHARED && len >= PUD_SIZE) >> + pud_size_align = true; > > This code will have duplicates in the next patch, so how about checking > this in a separate check routine? Good suggestion, thanks -- Mike Kravetz > > Thanks, > Naoya Horiguchi >