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

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Date:   Tue, 18 Oct 2016 14:52:47 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Ming Ling <ming.ling@...eadtrum.com>
Cc:     Minchan Kim <minchan@...nel.org>, 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 Tue 18-10-16 15:29:50, Minchan Kim wrote:
> On Mon, Oct 17, 2016 at 10:42:45AM +0200, Michal Hocko wrote:
[...]
> > Sure, what do you think about the following? I haven't marked it for
> > stable because there was no bug report for it AFAIU.
> > ---
> > From 3b2bd4486f36ada9f6dc86d3946855281455ba9f Mon Sep 17 00:00:00 2001
> > From: Ming Ling <ming.ling@...eadtrum.com>
> > Date: Mon, 17 Oct 2016 10:26:50 +0200
> > Subject: [PATCH] mm, compaction: fix NR_ISOLATED_* stats for pfn based
> >  migration
> > 
> > Since bda807d44454 ("mm: migrate: support non-lru movable page
> > migration") isolate_migratepages_block) can isolate !PageLRU pages which
> > would acct_isolated account as NR_ISOLATED_*. Accounting these non-lru
> > pages NR_ISOLATED_{ANON,FILE} doesn't make any sense and it can misguide
> > heuristics based on those counters such as pgdat_reclaimable_pages resp.
> > too_many_isolated which would lead to unexpected stalls during the
> > direct reclaim without any good reason. Note that
> > __alloc_contig_migrate_range can isolate a lot of pages at once.
> > 
> > On mobile devices such as 512M ram android Phone, it may use a big zram
> > swap. In some cases zram(zsmalloc) uses too many non-lru but migratedable
> > pages, such as:
> > 
> >       MemTotal: 468148 kB
> >       Normal free:5620kB
> >       Free swap:4736kB
> >       Total swap:409596kB
> >       ZRAM: 164616kB(zsmalloc non-lru pages)
> >       active_anon:60700kB
> >       inactive_anon:60744kB
> >       active_file:34420kB
> >       inactive_file:37532kB
> > 
> > Fix this by only accounting lru pages to NR_ISOLATED_* in
> > isolate_migratepages_block right after they were isolated and we still
> > know they were on LRU. Drop acct_isolated because it is called after the
> > fact and we've lost that information. Batching per-cpu counter doesn't
> > make much improvement anyway. Also make sure that we uncharge only LRU
> > pages when putting them back on the LRU in putback_movable_pages resp.
> > when unmap_and_move migrates the page.
> > 
> > Fixes: bda807d44454 ("mm: migrate: support non-lru movable page migration")
> > Signed-off-by: Ming Ling <ming.ling@...eadtrum.com>
> > Signed-off-by: Michal Hocko <mhocko@...e.com>
> 
> Acked-by: Minchan Kim <minchan@...nel.org>
> 
> with folding other fix patch you posted.

Thanks.

Ming, are you OK with this patch? Can I post it to Andrew?
-- 
Michal Hocko
SUSE Labs