On Tue 03-10-17 11:29:16, Pasha Tatashin wrote: > On 10/03/2017 09:18 AM, Michal Hocko wrote: > > On Wed 20-09-17 16:17:10, Pavel Tatashin wrote: > > > Some memory is reserved but unavailable: not present in memblock.memory > > > (because not backed by physical pages), but present in memblock.reserved. > > > Such memory has backing struct pages, but they are not initialized by going > > > through __init_single_page(). > > > > Could you be more specific where is such a memory reserved? > > > > I know of one example: trim_low_memory_range() unconditionally reserves from > pfn 0, but e820__memblock_setup() might provide the exiting memory from pfn > 1 (i.e. KVM). Then just initialize struct pages for that mapping rigth there where a special API is used. > But, there could be more based on this comment from linux/page-flags.h: > > 19 * PG_reserved is set for special pages, which can never be swapped out. > Some > 20 * of them might not even exist (eg empty_bad_page)... I have no idea wht empty_bad_page is but a quick grep shows that this is never used. I might be wrong here but if somebody is reserving a memory in a special way then we should handle the initialization right there. E.g. create an API for special memblock reservations. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
