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

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Date:   Fri, 14 Oct 2016 17:03:55 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     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 14-10-16 23:44:48, Minchan Kim wrote:
> 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.

diff --git a/mm/compaction.c b/mm/compaction.c
index 0409a4ad6ea1..6584705a46f6 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -685,7 +685,8 @@ static bool too_many_isolated(struct zone *zone)
  */
 static unsigned long
 isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
-			unsigned long end_pfn, isolate_mode_t isolate_mode)
+			unsigned long end_pfn, isolate_mode_t isolate_mode,
+			unsigned long *isolated_file, unsigned long *isolated_anon)
 {
 	struct zone *zone = cc->zone;
 	unsigned long nr_scanned = 0, nr_isolated = 0;
@@ -866,6 +867,10 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 
 		/* Successfully isolated */
 		del_page_from_lru_list(page, lruvec, page_lru(page));
+		if (page_is_file_cache(page))
+			(*isolated_file)++;
+		else
+			(*isolated_anon)++;
 
 isolate_success:
 		list_add(&page->lru, &cc->migratepages);

Makes more sense?
-- 
Michal Hocko
SUSE Labs