linux-kernel - Re: [PATCH 03/27] mm, vmscan: Move LRU lists to node

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Message-ID: <9c85cef1-32cc-5b99-0b95-8c8f0b14fd65@suse.cz>
Date:	Wed, 22 Jun 2016 14:50:57 +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 03/27] mm, vmscan: Move LRU lists to node

On 06/21/2016 04:15 PM, Mel Gorman wrote:
> This moves the LRU lists from the zone to the node and related data
> such as counters, tracing, congestion tracking and writeback tracking.
> Unfortunately, due to reclaim and compaction retry logic, it is necessary
> to account for the number of LRU pages on both zone and node logic. Most
> reclaim logic is based on the node counters but the retry logic uses
> the zone counters which do not distinguish inactive and inactive sizes.
> It would be possible to leave the LRU counters on a per-zone basis but
> it's a heavier calculation across multiple cache lines that is much
> more frequent than the retry checks.
>
> Other than the LRU counters, this is mostly a mechanical patch but note
> that it introduces a number of anomalies. For example, the scans are
> per-zone but using per-node counters. We also mark a node as congested
> when a zone is congested. This causes weird problems that are fixed later
> but is easier to review.
>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
> Acked-by: Johannes Weiner <hannes@...xchg.org>

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