linux-kernel - Re: [PATCH 2/2] mm/page_alloc: DEBUG_VM checks for free

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Message-Id: <20140508153433.7fcbe624549259b68659fe10@linux-foundation.org>
Date:	Thu, 8 May 2014 15:34:33 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Sasha Levin <sasha.levin@...cle.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Mel Gorman <mgorman@...e.de>,
	Yong-Taek Lee <ytk.lee@...sung.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Hugh Dickins <hughd@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Dave Jones <davej@...hat.com>
Subject: Re: [PATCH 2/2] mm/page_alloc: DEBUG_VM checks for free_list
 placement of CMA and RESERVE pages

On Thu, 8 May 2014 15:19:37 +0900 Minchan Kim <minchan@...nel.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 :(

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