From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934317AbcAYTwG (ORCPT ); Mon, 25 Jan 2016 14:52:06 -0500 Received: from e06smtp11.uk.ibm.com ([195.75.94.107]:58679 "EHLO e06smtp11.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934228AbcAYTwC (ORCPT ); Mon, 25 Jan 2016 14:52:02 -0500 X-IBM-Helo: d06dlp03.portsmouth.uk.ibm.com X-IBM-MailFrom: borntraeger@de.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org;linux-s390@vger.kernel.org Subject: Re: [PATCH/RFC] mm/debug_pagealloc: enable it by default To: Dave Jones , Joonsoo Kim , linux-kernel@vger.kernel.org, peterz@infradead.org, heiko.carstens@de.ibm.com, akpm@linux-foundation.org, linux-s390 References: <1453463080-84320-1-git-send-email-borntraeger@de.ibm.com> <20160125064151.GA22557@js1304-P5Q-DELUXE> <56A5DB21.2090300@de.ibm.com> <20160125192210.GA20919@codemonkey.org.uk> <20160125193820.GA22444@codemonkey.org.uk> From: Christian Borntraeger Message-ID: <56A67CDC.6080906@de.ibm.com> Date: Mon, 25 Jan 2016 20:51:56 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <20160125193820.GA22444@codemonkey.org.uk> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16012519-0041-0000-0000-00000748699B Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/25/2016 08:38 PM, Dave Jones wrote: > Content preview: On Mon, Jan 25, 2016 at 02:22:10PM -0500, Dave Jones wrote: > > > A default mode would be ok for me as it makes things obvious. Will send > > > a patch. > > The messaging around changing a default like this was really > poor. > When we do behaviour changes like this, we typically rename the CONFIG > option > to make it obvious that things aren't as they used to be. [...] > > Content analysis details: (-2.9 points, 5.0 required) > > pts rule name description > ---- ---------------------- -------------------------------------------------- > -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP > -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% > [score: 0.0000] > X-ZLA-Header: unknown; 0 > X-ZLA-DetailInfo: BA=6.00004114; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZH=6.00000000; ZP=6.00000000; ZU=6.00000002; UDB=6.00294159; UTC=2016-01-25 19:38:24 > x-cbid: 16012519-0041-0000-0000-0000074865D5 > X-IBM-ISS-SpamDetectors: Score=0.40962; FLB=0; FLI=0; BY=0; FL=0; FP=0; FZ=0; > HX=0; KW=0; PH=0; RB=0; SC=0.40962; ST=0; TS=0; UL=0; ISC= > X-IBM-ISS-DetailInfo: BY=3.00004831; HX=3.00000240; KW=3.00000007; > PH=3.00000004; SC=3.00000137; SDB=6.00650474; UDB=6.00294159; UTC=2016-01-25 > 19:38:24 > X-TM-AS-MML: disable > > On Mon, Jan 25, 2016 at 02:22:10PM -0500, Dave Jones wrote: > > > > A default mode would be ok for me as it makes things obvious. Will send > > > a patch. > > > > The messaging around changing a default like this was really poor. > > When we do behaviour changes like this, we typically rename the CONFIG option > > to make it obvious that things aren't as they used to be. > > Looking at this closer, shouldn't the original diff to make this runtime > have also changed the x86 implementation details in arch/x86/mm/pageattr.c ? > Even when we don't boot with the enable flag, we're doing the "split 2M page into 4Ks" > thing. It looks like a s/debug_pagealloc/debug_pagealloc_enabled()/ might > do the right thing maybe ? I have some patches ready, that fix the identity mapping for s390 and x86. sparc is hard to do as it allocates the TSB very early. Will send around what I have soon.