On 10/14/21 16:45, Kent Overstreet wrote: > On Wed, Oct 13, 2021 at 06:33:06PM +0200, David Hildenbrand wrote: >> > @@ -9317,6 +9319,7 @@ void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn) >> > struct page *page; >> > struct zone *zone; >> > unsigned int order; >> > + unsigned int migratetype; >> > unsigned long flags; >> > >> > offline_mem_sections(pfn, end_pfn); >> > @@ -9346,7 +9349,8 @@ void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn) >> > BUG_ON(page_count(page)); >> > BUG_ON(!PageBuddy(page)); >> > order = buddy_order(page); >> > - del_page_from_free_list(page, zone, order); >> > + migratetype = get_pfnblock_migratetype(page, pfn); >> >> As the free pages are isolated, theoretically this should be >> MIGRATE_ISOLATE. > > Thanks for noticing that - I somehow missed the fact that pageblock migratetypes > change at runtime, Not only that. Buddy merging will also merge pages from different migratetypes. I think that's the main reason why nr_free is not per migratetype. Your patch has been attempted few times already, e.g. here [1]. [1] https://lore.kernel.org/all/alpine.DEB.2.10.1611161731350.17379@xxxxxxxxxxxxxxxxxxxxxxxxx/ > so my patch is wrong. I'm going to have to rework my patch to > store the migratetype of free pages in the page itself. Yeah that would be the solution. Will likely bring some overhead to alloc/free fastpaths, which would have to be worth it, so nobody attempted it.
