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SubjectRe: [PATCH] mm: skip the page buddy block instead of one page
On 2013/8/15 12:17, Minchan Kim wrote:

>
> Please read full thread in detail.
>
> Mel suggested following as
>
> if (PageBuddy(page)) {
> int nr_pages = (1 << page_order(page)) - 1;
> if (PageBuddy(page)) {
> nr_pages = min(nr_pages, MAX_ORDER_NR_PAGES - 1);
> low_pfn += nr_pages;
> continue;
> }
> }
>
> min(nr_pages, xxx) removes your concern but I think Mel's version
> isn't right. It should be aligned with pageblock boundary so I
> suggested following.
>
> if (PageBuddy(page)) {
> #ifdef CONFIG_MEMORY_ISOLATION
> unsigned long order = page_order(page);
> if (PageBuddy(page)) {
> low_pfn += (1 << order) - 1;
> low_pfn = min(low_pfn, end_pfn);

Hi Minchan,

I understand now, but why use "end_pfn" here?
Do you mean we should use pageblock_nr_pages instead of MAX_ORDER_NR_PAGES?
Just like this:

if (PageBuddy(page)) {
unsigned long order = page_order(page);
order = min(order, pageblock_order);
if (PageBuddy(page))
low_pfn += (1 << order) - 1;
continue;
}

Thanks,
Xishi Qiu

> }
> #endif
> continue;
> }
>
> so worst case is (pageblock_nr_pages - 1).
> but we don't need to add CONFIG_MEMORY_ISOLATION so my suggestion
> is following as.
>
> if (PageBuddy(page)) {
> unsigned long order = page_order(page);
> if (PageBuddy(page)) {
> low_pfn += (1 << order) - 1;
> low_pfn = min(low_pfn, end_pfn);
> }
> continue;
> }
>
>





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