linux-kernel - Re: [PATCH 07/34] mm, vmscan: make kswapd reclaim in terms of nodes

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Message-Id: <20160831060959.GA6787@linux.vnet.ibm.com>
Date:   Wed, 31 Aug 2016 11:39:59 +0530
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>,
        Minchan Kim <minchan@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Hari Bathini <hbathini@...ux.vnet.ibm.com>
Subject: Re: [PATCH 07/34] mm, vmscan: make kswapd reclaim in terms of nodes

> > The trigger is memblock_reserve() for the complete node memory.  And
> > this is exactly what FA_DUMP does.  Here again the node has memory but
> > its all reserved so there is no free memory in the node.
> > 
> > Did you mean populated_zone() when you said zone_populated or have I
> > mistaken? populated_zone() does return 1 since it checks for
> > zone->present_pages.
> > 
> 
> Yes, I meant populated_zone(). Using present pages may have hidden
> a long-lived corner case as it was unexpected that an entire node
> would be reserved. The old code happened to survive *probably* because
> pgdat_reclaimable would look false and kswapd checks for pgdat being
> balanced would happen to do the right thing in this case.
> 
> Can you check if something like this works?
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index d572b78b65e1..cf64a5456cf6 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -830,7 +830,7 @@ unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
> 
>  static inline int populated_zone(struct zone *zone)
>  {
> -	return (!!zone->present_pages);
> +	return (!!zone->managed_pages);
>  }
> 
>  extern int movable_zone;
> 

This indeed fixes the problem.
Please add my 
Tested-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>