linux-kernel - Re: [PATCH 21/31] mm, page_alloc: Wake kswapd based on the highest eligible zone

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Date:	Tue, 5 Jul 2016 11:49:28 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Hillf Danton <hillf.zj@...baba-inc.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 21/31] mm, page_alloc: Wake kswapd based on the highest
 eligible zone

On Tue, Jul 05, 2016 at 02:57:38PM +0800, Hillf Danton wrote:
> > 
> > The ac_classzone_idx is used as the basis for waking kswapd and that is based
> > on the preferred zoneref. If the preferred zoneref's highest zone is lower
> > than what is available on other nodes, it's possible that kswapd is woken
> > on a zone with only higher, but still eligible, zones. As classzone_idx
> > is strictly adhered to now, it causes a problem because eligible pages
> > are skipped.
> > 
> > For example, node 0 has only DMA32 and node 1 has only NORMAL. An allocating
> > context running on node 0 may wake kswapd on node 1 telling it to skip
> > all NORMAL pages.
> > 
> > Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
> > ---
> Acked-by: Hillf Danton <hillf.zj@...baba-inc.com>
> 

Thanks. I also noticed when applying the ack that "zoneref's highest
zone" should have been "zoneref's first zone" so fixed that too.

-- 
Mel Gorman
SUSE Labs