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SubjectRe: [PATCH 15/17] mm/page_alloc: add informative debugging message in page_outside_zone_boundaries()
On 01/15/2013 04:24 PM, Cody P Schafer wrote:
> Add a debug message which prints when a page is found outside of the
> boundaries of the zone it should belong to. Format is:
> "page $pfn outside zone [ $start_pfn - $end_pfn ]"

I'd make sure to say 'pfn' here, just to make sure that it's explicitly
stated to be a pfn and not a 'struct page'

> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index f8ed277..f1783cf 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -239,13 +239,20 @@ static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
> int ret = 0;
> unsigned seq;
> unsigned long pfn = page_to_pfn(page);
> + unsigned long sp, start_pfn;

I think calling this zone_spanned is probably just fine. Shouldn't take
up too much room.

> do {
> seq = zone_span_seqbegin(zone);
> + start_pfn = zone->zone_start_pfn;
> + sp = zone->spanned_pages;
> if (!zone_spans_pfn(zone, pfn))
> ret = 1;
> } while (zone_span_seqretry(zone, seq));
>
> + if (ret)
> + pr_debug("page %lu outside zone [ %lu - %lu ]\n",
> + pfn, start_pfn, start_pfn + sp);
> +
> return ret;
> }

Is there a way we could also fit in something to disambiguate the zones?
I can imagine a scenario where two zones might have identical
start/spanned_pages, so they might be impossible to tell apart in a
message like this. Maybe we could add the NUMA node or the
DMA/Normal/Highmem text?



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