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From: Johannes Weiner <hannes@cmpxchg.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jia He <hejianet@gmail.com>, Mel Gorman <mgorman@suse.de>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	kernel-team@fb.com
Subject: Re: [PATCH 1/9] mm: fix 100% CPU kswapd busyloop on unreclaimable nodes
Date: Mon, 6 Mar 2017 11:24:10 -0500
Message-ID: <20170306162410.GB2090@cmpxchg.org> (raw)
In-Reply-To: <20170306013740.GA8779@bbox>

On Mon, Mar 06, 2017 at 10:37:40AM +0900, Minchan Kim wrote:
> On Fri, Mar 03, 2017 at 08:59:54AM +0100, Michal Hocko wrote:
> > On Fri 03-03-17 10:26:09, Minchan Kim wrote:
> > > On Tue, Feb 28, 2017 at 04:39:59PM -0500, Johannes Weiner wrote:
> > > > @@ -3316,6 +3325,9 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
> > > >  			sc.priority--;
> > > >  	} while (sc.priority >= 1);
> > > >  
> > > > +	if (!sc.nr_reclaimed)
> > > > +		pgdat->kswapd_failures++;
> > > 
> > > sc.nr_reclaimed is reset to zero in above big loop's beginning so most of time,
> > > it pgdat->kswapd_failures is increased.

That wasn't intentional; I didn't see the sc.nr_reclaimed reset.

---

>From e126db716926ff353b35f3a6205bd5853e01877b Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Mon, 6 Mar 2017 10:53:59 -0500
Subject: [PATCH] mm: fix 100% CPU kswapd busyloop on unreclaimable nodes fix

Check kswapd failure against the cumulative nr_reclaimed count, not
against the count from the lowest priority iteration.

Suggested-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/vmscan.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ddcff8a11c1e..b834b2dd4e19 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3179,9 +3179,9 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
 	count_vm_event(PAGEOUTRUN);
 
 	do {
+		unsigned long nr_reclaimed = sc.nr_reclaimed;
 		bool raise_priority = true;
 
-		sc.nr_reclaimed = 0;
 		sc.reclaim_idx = classzone_idx;
 
 		/*
@@ -3271,7 +3271,8 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
 		 * Raise priority if scanning rate is too low or there was no
 		 * progress in reclaiming pages
 		 */
-		if (raise_priority || !sc.nr_reclaimed)
+		nr_reclaimed = sc.nr_reclaimed - nr_reclaimed;
+		if (raise_priority || !nr_reclaimed)
 			sc.priority--;
 	} while (sc.priority >= 1);
 
-- 
2.11.1

  reply index

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-28 21:39 [PATCH 0/9] mm: kswapd spinning on unreclaimable nodes - fixes and cleanups Johannes Weiner
2017-02-28 21:39 ` [PATCH 1/9] mm: fix 100% CPU kswapd busyloop on unreclaimable nodes Johannes Weiner
2017-03-02  3:23   ` Hillf Danton
2017-03-02 23:30   ` Shakeel Butt
2017-03-03  1:26   ` Minchan Kim
2017-03-03  7:59     ` Michal Hocko
2017-03-06  1:37       ` Minchan Kim
2017-03-06 16:24         ` Johannes Weiner [this message]
2017-03-07  0:59           ` Hillf Danton
2017-03-07  7:28           ` Minchan Kim
2017-03-07 10:17           ` Michal Hocko
2017-03-07 16:56             ` Johannes Weiner
2017-03-09 14:20               ` Mel Gorman
2017-02-28 21:40 ` [PATCH 2/9] mm: fix check for reclaimable pages in PF_MEMALLOC reclaim throttling Johannes Weiner
2017-03-01 15:02   ` Michal Hocko
2017-03-02  3:25   ` Hillf Danton
2017-02-28 21:40 ` [PATCH 3/9] mm: remove seemingly spurious reclaimability check from laptop_mode gating Johannes Weiner
2017-03-01 15:06   ` Michal Hocko
2017-03-01 15:17   ` Mel Gorman
2017-03-02  3:27   ` Hillf Danton
2017-02-28 21:40 ` [PATCH 4/9] mm: remove unnecessary reclaimability check from NUMA balancing target Johannes Weiner
2017-03-01 15:14   ` Michal Hocko
2017-03-02  3:28   ` Hillf Danton
2017-02-28 21:40 ` [PATCH 5/9] mm: don't avoid high-priority reclaim on unreclaimable nodes Johannes Weiner
2017-03-01 15:21   ` Michal Hocko
2017-03-02  3:31   ` Hillf Danton
2017-02-28 21:40 ` [PATCH 6/9] mm: don't avoid high-priority reclaim on memcg limit reclaim Johannes Weiner
2017-03-01 15:40   ` Michal Hocko
2017-03-01 17:36     ` Johannes Weiner
2017-03-01 19:13       ` Michal Hocko
2017-03-02  3:32   ` Hillf Danton
2017-02-28 21:40 ` [PATCH 7/9] mm: delete NR_PAGES_SCANNED and pgdat_reclaimable() Johannes Weiner
2017-03-01 15:41   ` Michal Hocko
2017-03-02  3:34   ` Hillf Danton
2017-02-28 21:40 ` [PATCH 8/9] Revert "mm, vmscan: account for skipped pages as a partial scan" Johannes Weiner
2017-03-01 15:51   ` Michal Hocko
2017-03-02  3:36   ` Hillf Danton
2017-02-28 21:40 ` [PATCH 9/9] mm: remove unnecessary back-off function when retrying page reclaim Johannes Weiner
2017-03-01 14:56   ` Michal Hocko
2017-03-02  3:37   ` Hillf Danton

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