linux-kernel - Re: [PATCH 06/27] mm, vmscan: Begin reclaiming pages on a per-node basis

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Message-ID: <20160223190346.GG13816@cmpxchg.org>
Date:	Tue, 23 Feb 2016 11:03:46 -0800
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/27] mm, vmscan: Begin reclaiming pages on a per-node
 basis

On Tue, Feb 23, 2016 at 10:57:22AM -0800, Johannes Weiner wrote:
> > @@ -2558,16 +2579,12 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
> >  		sc->gfp_mask |= __GFP_HIGHMEM;
> >  
> >  	for_each_zone_zonelist_nodemask(zone, z, zonelist,
> > -					requested_highidx, sc->nodemask) {
> 
> It's unfortunate that we start with the lowest zone here. For Normal
> allocations, the most common allocations, this will always have two
> full shrink_node() rounds that skip over everything >DMA in the first,
> then over everything >DMA32 in the second, even though all pages on
> the node are valid reclaim candidates for that allocation.

Nevermind, I'm confused about zonelist ordering. It starts with the
highest indexed zones.