From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933473AbcAYTie (ORCPT ); Mon, 25 Jan 2016 14:38:34 -0500 Received: from arcturus.aphlor.org ([188.246.204.175]:49194 "EHLO arcturus.aphlor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933146AbcAYTi3 (ORCPT ); Mon, 25 Jan 2016 14:38:29 -0500 Date: Mon, 25 Jan 2016 14:38:20 -0500 From: Dave Jones To: Christian Borntraeger , Joonsoo Kim , linux-kernel@vger.kernel.org, peterz@infradead.org, heiko.carstens@de.ibm.com, akpm@linux-foundation.org, linux-s390 Subject: Re: [PATCH/RFC] mm/debug_pagealloc: enable it by default Message-ID: <20160125193820.GA22444@codemonkey.org.uk> Mail-Followup-To: Dave Jones , Christian Borntraeger , 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160125192210.GA20919@codemonkey.org.uk> User-Agent: Mutt/1.5.24 (2015-08-30) X-Spam-Score: -2.9 (--) X-Spam-Report: Spam detection software, running on the system "arcturus.aphlor.org", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. 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] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 ? It's almost comedic that I walked into change c9e0d39126af thinking all this stuff was working _because_ we were doing that page splitting. Dave