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Date: Thu, 11 Feb 2010 12:25:08 +0000
From: Mel Gorman <mel@csn.ul.ie>
Subject: Re: [patch] mm: suppress pfn range output for zones without pages
Message-ID: <20100211122507.GA32292@csn.ul.ie>
References: <alpine.DEB.2.00.1002110129280.3069@chino.kir.corp.google.com>
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Sender: owner-linux-mm@kvack.org
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>

On Thu, Feb 11, 2010 at 01:29:58AM -0800, David Rientjes wrote:
> free_area_init_nodes() emits pfn ranges for all zones on the system.
> There may be no pages on a higher zone, however, due to memory
> limitations or the use of the mem= kernel parameter.  For example:
> 
> Zone PFN ranges:
>   DMA      0x00000001 -> 0x00001000
>   DMA32    0x00001000 -> 0x00100000
>   Normal   0x00100000 -> 0x00100000
> 
> The implementation copies the previous zone's highest pfn, if any, as the
> next zone's lowest pfn.  If its highest pfn is then greater than the
> amount of addressable memory, the upper memory limit is used instead.
> Thus, both the lowest and highest possible pfn for higher zones without
> memory may be the same.
> 
> The output is now suppressed for zones that do not have a valid pfn
> range.
> 

I see no problem with the patch. Was it a major problem or just
confusing?

> Cc: Mel Gorman <mel@csn.ul.ie>
> Signed-off-by: David Rientjes <rientjes@google.com>

Reviewed-by: Mel Gorman <mel@csn.ul.ie>

> ---
>  mm/page_alloc.c       |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4377,6 +4377,9 @@ void __init free_area_init_nodes(unsigned long *max_zone_pfn)
>  	for (i = 0; i < MAX_NR_ZONES; i++) {
>  		if (i == ZONE_MOVABLE)
>  			continue;
> +		if (arch_zone_lowest_possible_pfn[i] ==
> +		    arch_zone_highest_possible_pfn[i])
> +			continue;
>  		printk("  %-8s %0#10lx -> %0#10lx\n",
>  				zone_names[i],
>  				arch_zone_lowest_possible_pfn[i],
> 

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

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