linux-kernel - Re: [PATCH 22/34] mm, page_alloc: wake kswapd based on the highest eligible zone

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Message-ID: <20160712172446.GB7307@cmpxchg.org>
Date:	Tue, 12 Jul 2016 13:24:46 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Minchan Kim <minchan@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 22/34] mm, page_alloc: wake kswapd based on the highest
 eligible zone

On Fri, Jul 08, 2016 at 10:34:58AM +0100, Mel Gorman 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 first 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>

Acked-by: Johannes Weiner <hannes@...xchg.org>