From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-f181.google.com (mail-ie0-f181.google.com [209.85.223.181]) by kanga.kvack.org (Postfix) with ESMTP id 6259F6B0069 for ; Wed, 26 Nov 2014 15:49:39 -0500 (EST) Received: by mail-ie0-f181.google.com with SMTP id tp5so3370988ieb.40 for ; Wed, 26 Nov 2014 12:49:39 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id h12si4203514ici.1.2014.11.26.12.49.37 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 26 Nov 2014 12:49:38 -0800 (PST) Date: Wed, 26 Nov 2014 12:49:36 -0800 From: Andrew Morton 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> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: 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 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org