From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754649AbcIMLkO (ORCPT ); Tue, 13 Sep 2016 07:40:14 -0400 Received: from mail-wm0-f51.google.com ([74.125.82.51]:35120 "EHLO mail-wm0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753762AbcIMLkF (ORCPT ); Tue, 13 Sep 2016 07:40:05 -0400 Date: Tue, 13 Sep 2016 14:40:01 +0300 From: "Kirill A. Shutemov" To: Rui Teng Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Michal Hocko , Naoya Horiguchi , Chen Gang , "Kirill A . Shutemov" , Vlastimil Babka , "Aneesh Kumar K . V" , hejianet@linux.vnet.ibm.com Subject: Re: [RFC] mm: Change the data type of huge page size from unsigned long to u64 Message-ID: <20160913114001.GB31186@node> References: <1473758765-13673-1-git-send-email-rui.teng@linux.vnet.ibm.com> <20160913093257.GA31186@node> <09ab7941-07fa-0003-46d8-9fa5c07eba2d@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <09ab7941-07fa-0003-46d8-9fa5c07eba2d@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 13, 2016 at 07:21:07PM +0800, Rui Teng wrote: > On 9/13/16 5:32 PM, Kirill A. Shutemov wrote: > >On Tue, Sep 13, 2016 at 05:26:05PM +0800, Rui Teng wrote: > >>The huge page size could be 16G(0x400000000) on ppc64 architecture, and it will > >>cause an overflow on unsigned long data type(0xFFFFFFFF). > > > >Huh? ppc64 is 64-bit system and sizeof(void *) is equal to > >sizeof(unsigned long) on Linux (LP64 model). > > > >So where your 0xFFFFFFFF comes from? > > > The size of unsigned long data type is 4 bytes No, it's not. -- Kirill A. Shutemov