From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755915AbaEHWeh (ORCPT <rfc822;w@1wt.eu>);
	Thu, 8 May 2014 18:34:37 -0400
Received: from mail.linuxfoundation.org ([140.211.169.12]:42251 "EHLO
	mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753994AbaEHWef (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 8 May 2014 18:34:35 -0400
Date: Thu, 8 May 2014 15:34:33 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>, Vlastimil Babka <vbabka@suse.cz>,
        Sasha Levin <sasha.levin@oracle.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Mel Gorman <mgorman@suse.de>, Yong-Taek Lee <ytk.lee@samsung.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Hugh Dickins <hughd@google.com>, Rik van Riel <riel@redhat.com>,
        Michal Nazarewicz <mina86@mina86.com>, Dave Jones <davej@redhat.com>
Subject: Re: [PATCH 2/2] mm/page_alloc: DEBUG_VM checks for free_list
 placement of CMA and RESERVE pages
Message-Id: <20140508153433.7fcbe624549259b68659fe10@linux-foundation.org>
In-Reply-To: <20140508061937.GE5282@bbox>
References: <533D8015.1000106@suse.cz>
	<1396539618-31362-1-git-send-email-vbabka@suse.cz>
	<1396539618-31362-2-git-send-email-vbabka@suse.cz>
	<53616F39.2070001@oracle.com>
	<53638ADA.5040200@suse.cz>
	<5367A1E5.2020903@oracle.com>
	<5367B356.1030403@suse.cz>
	<20140507013333.GB26212@bbox>
	<536A4A3B.1090403@suse.cz>
	<20140508055421.GC9161@js1304-P5Q-DELUXE>
	<20140508061937.GE5282@bbox>
X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; 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: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, 8 May 2014 15:19:37 +0900 Minchan Kim <minchan@kernel.org> wrote:

> > I also think that VM_DEBUG overhead isn't problem because of same
> > reason from Vlastimil.
> 
> Guys, please read this.
> 
> https://lkml.org/lkml/2013/7/17/591
> 
> If you guys really want it, we could separate it with
> CONFIG_DEBUG_CMA or CONFIG_DEBUG_RESERVE like stuff.
> Otherwise, just remain in mmotm.

Wise words, those.

Yes, these checks are in a pretty hot path.  I'm inclined to make the
patch -mm (and -next) only.

Unless there's a really good reason, such as "nobody who uses CMA is
likely to be testing -next", which sounds likely :(