Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752497AbaKZUtj (ORCPT ); Wed, 26 Nov 2014 15:49:39 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:43061 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750979AbaKZUti (ORCPT ); Wed, 26 Nov 2014 15:49:38 -0500 Date: Wed, 26 Nov 2014 12:49:36 -0800 From: Andrew Morton To: Joonsoo Kim Cc: Mel Gorman , Johannes Weiner , Minchan Kim , Dave Hansen , Michal Nazarewicz , Jungsoo Son , Ingo Molnar , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/8] mm/debug-pagealloc: make debug-pagealloc boottime configurable Message-Id: <20141126124936.56cc901e13f27927d7b42aaf@linux-foundation.org> In-Reply-To: <20141124234237.GA7824@js1304-P5Q-DELUXE> References: <1416816926-7756-1-git-send-email-iamjoonsoo.kim@lge.com> <1416816926-7756-4-git-send-email-iamjoonsoo.kim@lge.com> <20141124145542.08b97076.akpm@linux-foundation.org> <20141124234237.GA7824@js1304-P5Q-DELUXE> X-Mailer: Sylpheed 3.4.0beta7 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 25 Nov 2014 08:42:37 +0900 Joonsoo Kim wrote: > On Mon, Nov 24, 2014 at 02:55:42PM -0800, Andrew Morton wrote: > > On Mon, 24 Nov 2014 17:15:21 +0900 Joonsoo Kim wrote: > > > > > Now, we have prepared to avoid using debug-pagealloc in boottime. So > > > introduce new kernel-parameter to disable debug-pagealloc in boottime, > > > and makes related functions to be disabled in this case. > > > > > > Only non-intuitive part is change of guard page functions. Because > > > guard page is effective only if debug-pagealloc is enabled, turning off > > > according to debug-pagealloc is reasonable thing to do. > > > > > > ... > > > > > > --- a/Documentation/kernel-parameters.txt > > > +++ b/Documentation/kernel-parameters.txt > > > @@ -858,6 +858,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > > > causing system reset or hang due to sending > > > INIT from AP to BSP. > > > > > > + disable_debug_pagealloc > > > + [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this > > > + parameter allows user to disable it at boot time. > > > + With this parameter, we can avoid allocating huge > > > + chunk of memory for debug pagealloc and then > > > + the system will work mostly same with the kernel > > > + built without CONFIG_DEBUG_PAGEALLOC. > > > + > > > > Weren't we going to make this default to "off", require a boot option > > to turn debug_pagealloc on? > > Hello, Andrew. > > I'm afraid that changing default to "off" confuses some old users. > They would expect that it is default "on". But, it is just debug > feature, so, it may be no problem. If you prefer to change default, I > will rework this patch. Please let me know your decision. I suspect the number of "old users" is one ;) I think it would be better to default to off - that's the typical behaviour for debug features, for good reasons. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/