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From: Mel Gorman <mgorman@techsingularity.net>
To: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: "'Andrew Morton'" <akpm@linux-foundation.org>,
	"'Shantanu Goel'" <sgoel01@yahoo.com>,
	"'Chris Mason'" <clm@fb.com>,
	"'Johannes Weiner'" <hannes@cmpxchg.org>,
	"'Vlastimil Babka'" <vbabka@suse.cz>,
	"'LKML'" <linux-kernel@vger.kernel.org>,
	"'Linux-MM'" <linux-mm@kvack.org>
Subject: Re: [PATCH 3/3] mm, vmscan: Prevent kswapd sleeping prematurely due to mismatched classzone_idx
Date: Thu, 16 Feb 2017 08:10:39 +0000	[thread overview]
Message-ID: <20170216081039.ukbxl2b4khnwwbic@techsingularity.net> (raw)
In-Reply-To: <001501d2881d$242aa790$6c7ff6b0$@alibaba-inc.com>

On Thu, Feb 16, 2017 at 02:23:08PM +0800, Hillf Danton wrote:
> On February 15, 2017 5:23 PM Mel Gorman wrote: 
> >   */
> >  static int kswapd(void *p)
> >  {
> > -	unsigned int alloc_order, reclaim_order, classzone_idx;
> > +	unsigned int alloc_order, reclaim_order;
> > +	unsigned int classzone_idx = MAX_NR_ZONES - 1;
> >  	pg_data_t *pgdat = (pg_data_t*)p;
> >  	struct task_struct *tsk = current;
> > 
> > @@ -3447,20 +3466,23 @@ static int kswapd(void *p)
> >  	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
> >  	set_freezable();
> > 
> > -	pgdat->kswapd_order = alloc_order = reclaim_order = 0;
> > -	pgdat->kswapd_classzone_idx = classzone_idx = 0;
> > +	pgdat->kswapd_order = 0;
> > +	pgdat->kswapd_classzone_idx = MAX_NR_ZONES;
> >  	for ( ; ; ) {
> >  		bool ret;
> > 
> > +		alloc_order = reclaim_order = pgdat->kswapd_order;
> > +		classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx);
> > +
> >  kswapd_try_sleep:
> >  		kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
> >  					classzone_idx);
> > 
> >  		/* Read the new order and classzone_idx */
> >  		alloc_order = reclaim_order = pgdat->kswapd_order;
> > -		classzone_idx = pgdat->kswapd_classzone_idx;
> > +		classzone_idx = kswapd_classzone_idx(pgdat, 0);
> >  		pgdat->kswapd_order = 0;
> > -		pgdat->kswapd_classzone_idx = 0;
> > +		pgdat->kswapd_classzone_idx = MAX_NR_ZONES;
> > 
> >  		ret = try_to_freeze();
> >  		if (kthread_should_stop())
> > @@ -3486,9 +3508,6 @@ static int kswapd(void *p)
> >  		reclaim_order = balance_pgdat(pgdat, alloc_order, classzone_idx);
> >  		if (reclaim_order < alloc_order)
> >  			goto kswapd_try_sleep;
> 
> If we fail order-5 request,  can we then give up order-5, and
> try order-3 if requested, after napping?
> 

That has no bearing upon this patch. At this point, kswapd has stopped
reclaiming at the requested order and is preparing to sleep. If there is
a parallel request for order-3 while it's sleeping, it'll wake and start
reclaiming at order-3 as requested.

-- 
Mel Gorman
SUSE Labs

  reply	other threads:[~2017-02-16  8:10 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-15  9:22 [PATCH 0/3] Reduce amount of time kswapd sleeps prematurely Mel Gorman
2017-02-15  9:22 ` [PATCH 1/3] mm, vmscan: fix zone balance check in prepare_kswapd_sleep Mel Gorman
2017-02-16  2:50   ` Hillf Danton
2017-02-22  7:00   ` Minchan Kim
2017-02-23 15:05     ` Mel Gorman
2017-02-24  1:17       ` Minchan Kim
2017-02-24  9:11         ` Mel Gorman
2017-02-27  6:16           ` Minchan Kim
2017-02-15  9:22 ` [PATCH 2/3] mm, vmscan: Only clear pgdat congested/dirty/writeback state when balanced Mel Gorman
2017-02-15  9:22 ` [PATCH 3/3] mm, vmscan: Prevent kswapd sleeping prematurely due to mismatched classzone_idx Mel Gorman
2017-02-16  6:23   ` Hillf Danton
2017-02-16  8:10     ` Mel Gorman [this message]
2017-02-16  8:21       ` Hillf Danton
2017-02-16  9:32         ` Mel Gorman
2017-02-20 16:34         ` Vlastimil Babka
2017-02-21  4:10           ` Hillf Danton
2017-02-20 16:42   ` Vlastimil Babka
2017-02-23 15:01     ` Mel Gorman
2017-03-01  9:04       ` Vlastimil Babka
2017-02-15 20:30 ` [PATCH 0/3] Reduce amount of time kswapd sleeps prematurely Andrew Morton
2017-02-15 21:29   ` Mel Gorman
2017-02-15 21:56     ` Andrew Morton
2017-02-15 22:15       ` Mel Gorman
2017-02-15 22:00     ` Vlastimil Babka
2017-03-09  7:56 [PATCH 0/3] Reduce amount of time kswapd sleeps prematurely v2 Mel Gorman
2017-03-09  7:56 ` [PATCH 3/3] mm, vmscan: Prevent kswapd sleeping prematurely due to mismatched classzone_idx Mel Gorman

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