linux-kernel - Re: [PATCH 00/34] Move LRU page reclaim from zones to nodes v9

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Message-ID: <5a560eab-cdf9-1961-1216-deff50cdf494@suse.cz>
Date:   Fri, 19 Aug 2016 15:23:20 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Andrea Arcangeli <aarcange@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Minchan Kim <minchan@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/34] Move LRU page reclaim from zones to nodes v9

On 08/19/2016 03:12 PM, Andrea Arcangeli wrote:
> Hello Mel,

Hi Andrea,

> On Fri, Jul 08, 2016 at 10:34:36AM +0100, Mel Gorman wrote:
>> Minor changes this time
>>
>> Changelog since v8
>> This is the latest version of a series that moves LRUs from the zones to
>
> I'm afraid this is a bit incomplete...
>
> I had troubles in rebasing the compaction-enabled zone_reclaim feature
> (now node_reclaim) to the node model.

What's that? Never head of this before, but sounds scary :) I thought 
that zone_reclaim itself was rather discouraged nowadays, not a big 
candidate for further improvement.,,

> That is because compaction is
> still zone based, and so I would need to do a loop of compaction calls
> (for each zone in the node), but what's the point? Movable memory can
> always go anywhere, can't it?

Hm I'm not so sure. Are all movable allocations highmem? For example 
Joonsoo mentions in his ZONE_CMA patchset "blockdev file cache page 
[...] usually has __GFP_MOVABLE but not __GFP_HIGHMEM and __GFP_USER".
Now we also have Minchan's infrastructure for arbitrary driver 
compaction, so those will be movable, but potentially still restricted 
to e.g. DMA32...

Vlastimil