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

[Vlastimil Babka]

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