On 03/20/24 at 04:18pm, Baoquan He wrote: > On 03/19/24 at 06:17pm, Mike Rapoport wrote: > > On Mon, Mar 18, 2024 at 10:21:36PM +0800, Baoquan He wrote: > > > Currently, in free_area_init_core(), when initialize zone's field, a > > > rough value is set to zone->managed_pages. That value is calculated by > > > (zone->present_pages - memmap_pages). > > > > > > In the meantime, add the value to nr_all_pages and nr_kernel_pages which > > > represent all free pages of system (only low memory or including HIGHMEM > > > memory separately). Both of them are gonna be used in > > > alloc_large_system_hash(). > > > > > > However, the rough calculation and setting of zone->managed_pages is > > > meaningless because > > > a) memmap pages are allocated on units of node in sparse_init() or > > > alloc_node_mem_map(pgdat); The simple (zone->present_pages - > > > memmap_pages) is too rough to make sense for zone; > > > b) the set zone->managed_pages will be zeroed out and reset with > > > acutal value in mem_init() via memblock_free_all(). Before the > > > resetting, no buddy allocation request is issued. > > > > > > Here, remove the meaningless and complicated calculation of > > > (zone->present_pages - memmap_pages), directly set zone->present_pages to > > > zone->managed_pages. It will be adjusted in mem_init(). > > > > Do you mean "set zone->managed_pages to zone->present_pages"? > > Hmm, maybe 'set zone->managed_pages as zone->present_pages' > or > 'assign zone->present_pages to zone->managed_pages' > which is more precise. > > Wwill update. > > > > > I think we can just set zone->managed_pages to 0 in free_area_init_core(). > > Anyway it will be reset before the first use. Rethink about this, it's better to set zone->managed_pages to 0 because there isn't any page added to buddy. Will update. > > Yeah, setting to 0 is also fine. I thougt of 0 ever. Considering > zone->present_pages is closer value to actual zone->managed_pages > than 0, and it may be needed in the future in some way before > mem_init(). If no strong objection, I will keep the assigning > 'zone->present_pages' to 'zone->managed_pages'. > > Thanks again for careful reviewing. >
