linux-kernel - Re: [PATCH 18/34] mm: rename NR_ANON_PAGES to NR_ANON

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Message-ID: <20160713085516.GI9806@techsingularity.net>
Date:	Wed, 13 Jul 2016 09:55:16 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Minchan Kim <minchan@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 18/34] mm: rename NR_ANON_PAGES to NR_ANON_MAPPED

On Tue, Jul 12, 2016 at 10:58:01AM -0400, Johannes Weiner wrote:
> On Fri, Jul 08, 2016 at 10:34:54AM +0100, Mel Gorman wrote:
> > NR_FILE_PAGES  is the number of        file pages.
> > NR_FILE_MAPPED is the number of mapped file pages.
> > NR_ANON_PAGES  is the number of mapped anon pages.
> > 
> > This is unhelpful naming as it's easy to confuse NR_FILE_MAPPED and
> > NR_ANON_PAGES for mapped pages.  This patch renames NR_ANON_PAGES so we
> > have
> > 
> > NR_FILE_PAGES  is the number of        file pages.
> > NR_FILE_MAPPED is the number of mapped file pages.
> > NR_ANON_MAPPED is the number of mapped anon pages.
> 
> That looks wrong to me. The symmetry is between NR_FILE_PAGES and
> NR_ANON_PAGES. NR_FILE_MAPPED is merely elaborating on the mapped
> subset of NR_FILE_PAGES, something which isn't necessary for anon
> pages as they're always mapped.

How strongly do you feel about reverting it as later patches would cause
lots of conflicts.

Obviously I found the new names clearer but I was thinking a lot at the
time about mapped vs unmapped due to looking closely at both reclaim and
[f|m]advise functions at the time. I found it mildly irksome to switch
between the semantics of file/anon when looking at the vmstat updates.

-- 
Mel Gorman
SUSE Labs