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

From: Srikar Dronamraju <[email-masked]>
Date: Wed, 31 Aug 2016 11:39:59 +0530

> > 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 <[email-masked]>