Re: [RFC] memory-layout-free zones (for review) [3/3] fix for_each_page_in_zone

KAMEZAWA Hiroyuki
2006-02-24T00:03:17Z

Dave Hansen wrote:
> I know we don't use this function _too_ much , but it would probably be
> nice to make it a little smarter than "i++". We can be pretty sure, at
> least with SPARSEMEM that the granularity is larger than that. We can
> probably leave it until it gets to be a real problem.
Yes, SPARSEMEM can skip PAGES_PER_SECTION pages if !pfn_valid()

>
> I was also trying to think if a binary search is appropriate here. I
> guess it depends on whether we allow the zones to have overlapping pfn
> ranges, which I _think_ is one of the goals from these patches. Any
> thoughts?
>
What I'm thinking of is to allow zones to have overlapping pfn ranges.
Showing benefit of it (by patch) is difficult now but I think it's sane
direction.

> Oh, and I noticed the "pgdat->zone_spanned_pages" bit. Did you compile
> this? ;)
>
No (>_<
>> +static inline struct page *next_page_in_zone(struct page *page,
>> + struct zone *zone)
>> +{
>> + struct pglist_data *pgdat;
>> + unsigned long start_pfn;
>> + unsigned long i;
>> +
>> + if (!populated_zone(zone))
>> + return NULL;
>> + pgdat = zone->zone_pgdat;
>> + start_pfn = pgdat->node_start_pfn;
>> + i = page_to_pfn(page) - start_pfn;
>> +
>> + for (i = i + 1; i < pgdat->node_spanned_pages; i++) {
>> + if (pfn_vlaid(start_pfn + i) && page_zone(page) == zone)
>> + break;
>> + }
>> + if (i == pgdat->node_spanned_pages)
>> + return NULL;
>> + return pfn_to_page(start_pfn + i);
>> +}
>
> Same comment, BTW, about code sharing. Is it something we want to or
> can do with these?
>
Hmm...I can't find it. I'll rewrite this code as out-of-line function and
add optimizaion by its memory_model, and do more cleanup.

I'll post these again to -mm before going lkml, and will do compile them in
the next time....

-- Kame