Alexey Dobriyan <[email protected]> writes:
>
> +/* Return the page with the lowest PFN in the list */
> +static struct page *min_page(struct list_head *list)
> +{
> + unsigned long min_pfn = -1UL;
> + struct page *min_page = NULL, *page;;
> +
> + list_for_each_entry(page, list, lru) {
> + unsigned long pfn = page_to_pfn(page);
> + if (pfn < min_pfn) {
> + min_pfn = pfn;
> + min_page = page;
> + }
> + }
> +
> + return min_page;
> +}
> +
> /* Remove an element from the buddy allocator from the fallback list */
> static struct page *__rmqueue_fallback(struct zone *zone, int order,
> int start_migratetype)
> @@ -795,8 +812,11 @@ retry:
> if (list_empty(&area->free_list[migratetype]))
> continue;
>
> + /* Bias kernel allocations towards low pfns */
> page = list_entry(area->free_list[migratetype].next,
> struct page, lru);
> + if (unlikely(start_migratetype != MIGRATE_MOVABLE))
> + page = min_page(&area->free_list[migratetype]);
Do I misread this, or does it really turn the O(1) buddy allocation into
a "search whole free list" algorithm? Even as fallback that looks like
a quite extreme thing to do.
-Andi
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