linux-kernel - Re: [PATCH v2] mm: exclude isolated non-lru pages from NR_ISOLATED_ANON or NR_ISOLATED

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Message-ID: <20161014144448.GA2899@blaptop>
Date:   Fri, 14 Oct 2016 23:44:48 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Minchan Kim <minchan@...nel.org>,
        Ming Ling <ming.ling@...eadtrum.com>,
        akpm@...ux-foundation.org, mgorman@...hsingularity.net,
        vbabka@...e.cz, hannes@...xchg.org, baiyaowei@...s.chinamobile.com,
        iamjoonsoo.kim@....com, rientjes@...gle.com, hughd@...gle.com,
        kirill.shutemov@...ux.intel.com, riel@...hat.com, mgorman@...e.de,
        aquini@...hat.com, corbet@....net, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, orson.zhai@...eadtrum.com,
        geng.ren@...eadtrum.com, chunyan.zhang@...eadtrum.com,
        zhizhou.tian@...eadtrum.com, yuming.han@...eadtrum.com,
        xiajing@...eadst.com
Subject: Re: [PATCH v2] mm: exclude isolated non-lru pages from
 NR_ISOLATED_ANON or NR_ISOLATED_FILE.

On Fri, Oct 14, 2016 at 03:53:34PM +0200, Michal Hocko wrote:
> On Fri 14-10-16 22:46:04, Minchan Kim wrote:
> [...]
> > > > > Why don't you simply mimic what shrink_inactive_list does? Aka count the
> > > > > number of isolated pages and then account them when appropriate?
> > > > >
> > > > I think i am correcting clearly wrong part. So, there is no need to
> > > > describe it too detailed. It's a misunderstanding, and i will add
> > > > more comments as you suggest.
> > > 
> > > OK, so could you explain why you prefer to relyon __PageMovable rather
> > > than do a trivial counting during the isolation?
> > 
> > I don't get it. Could you elaborate it a bit more?
> 
> It is really simple. You can count the number of file and anonymous
> pages while they are isolated and then account them to NR_ISOLATED_*
> later. Basically the same thing we do during the reclaim. We absolutely
> do not have to rely on __PageMovable and make this code more complex
> than necessary.

I don't understand your point.
isolate_migratepages_block can isolate any movable pages, for instance,
anon, file and non-lru and they are isolated into cc->migratepges.
Then, acct_isolated accounts them to NR_ISOLATED_*.
Isn't it same with the one you suggested?
The problem is we should identify which pages is non-lru movable first.
If it's not non-lru, it means the page is either anon or file so we
can account them. 
That's exactly waht Ming Ling did.

Sorry if I didn't get your point. Maybe, it would be better to give
pseudo code out of your mind for better understanding rather than
several ping-ping with vague words.

Thanks.