On Wed, 11 Mar 2009 21:00:22 +0800
Wu Fengguang <fengguang.wu@intel.com> wrote:

> 
> I worked up a simple debugging patch. Since the missing pages are
> continuously spanned, several stack dumping shall be enough to catch
> the page consumer.
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 27b8681..c0df7fd 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1087,6 +1087,13 @@ again:
>  			goto failed;
>  	}
>  
> +	/* wfg - hunting the 40000 missing pages */
> +	{
> +		unsigned long pfn = page_to_pfn(page);
> +		if (pfn > 0x1000 && (pfn & 0xfff) <= 1)
> +			dump_stack();
> +	}
> +
>  	__count_zone_vm_events(PGALLOC, zone, 1 << order);
>  	zone_statistics(preferred_zone, zone);
>  	local_irq_restore(flags);

This got very noisy, but here's what was in the ring buffer once it had
booted.

Note that this is where only the "noflags" pages have been allocated,
not "lru".

Rgds
-- 
     -- Pierre Ossman

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