Re: [PATCH v2] mm: exclude isolated non-lru pages from NR_ISOLATED_ANON or NR_ISOLATED_FILE.

[Ming Ling]

ä, 10æ 18, 2016 at 02:52:47äå +0200, Michal Hocko wrote:
hi,
> 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@xxxxxxxxxxxxxx>
> > > 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@xxxxxxxxxxxxxx>
> > > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> > 
> > Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
> > 
> > with folding other fix patch you posted.
> 
> Thanks.
> 
> Ming, are you OK with this patch? Can I post it to Andrew?
> --
I think that's fine. Just do it.
Thank you.
> Michal Hocko
> SUSE Labs