linux-kernel - Re: [PATCH 06/27] mm, vmscan: Make kswapd reclaim in terms of nodes

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Message-ID: <0973a4bd-ec85-b6f2-02a4-25b787675e01@suse.cz>
Date:	Wed, 15 Jun 2016 16:23:12 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Mel Gorman <mgorman@...hsingularity.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>
Cc:	Rik van Riel <riel@...riel.com>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/27] mm, vmscan: Make kswapd reclaim in terms of nodes

On 06/09/2016 08:04 PM, Mel Gorman wrote:
> Patch "mm: vmscan: Begin reclaiming pages on a per-node basis" started
> thinking of reclaim in terms of nodes but kswapd is still zone-centric. This
> patch gets rid of many of the node-based versus zone-based decisions.
>
> o A node is considered balanced when any eligible lower zone is balanced.
>   This eliminates one class of age-inversion problem because we avoid
>   reclaiming a newer page just because it's in the wrong zone
> o pgdat_balanced disappears because we now only care about one zone being
>   balanced.
> o Some anomalies related to writeback and congestion tracking being based on
>   zones disappear.
> o kswapd no longer has to take care to reclaim zones in the reverse order
>   that the page allocator uses.
> o Most importantly of all, reclaim from node 0 with multiple zones will
>   have similar aging and reclaiming characteristics as every
>   other node.
>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
> Acked-by: Johannes Weiner <hannes@...xchg.org>

Acked-by: Vlastimil Babka <vbabka@...e.cz>