On 05.04.19 12:30, Michal Hocko wrote: > On Fri 05-04-19 10:05:09, David Hildenbrand wrote: >> On 05.04.19 09:14, Michal Hocko wrote: >>> On Thu 04-04-19 20:27:41, David Hildenbrand wrote: >>>> On 04.04.19 20:01, Oscar Salvador wrote: >>> [...] >>>>> But I am not really convinced by MHP_SYSTEM_RAM name, and I think we should stick >>>>> with MHP_MEMBLOCK_API because it represents __what__ is that flag about and its >>>>> function, e.g: create memory block devices. >>> >>> Exactly >> >> Fine with me for keeping what Oscar has. >> >>> >>>> This nicely aligns with the sub-section memory add support discussion. >>>> >>>> MHP_MEMBLOCK_API immediately implies that >>>> >>>> - memory is used as system ram. Memory can be onlined/offlined. Markers >>>> at sections indicate if the section is online/offline. >>> >>> No there is no implication like that. It means only that the onlined >>> memory has a sysfs interface. Nothing more, nothing less >> >> As soon as there is a online/offline interface, you *can* (and user >> space usually *will*) online that memory. Onlining/offlining is only >> defined for memory to be added to the buddy - memory to be used as >> "system ram". Doing it for random device memory will not work / result >> in undefined behavior. > > No, not really. We really do not care where the memory comes from. Is it > RAM, NVDIMM, $FOO_BAR_OF_A_FUTURE_BUZZ. We only do care that the memory > can be onlined - user triggered associated with a zone. The memory even > doesn't have to go to the page allocator. > Yes, true, I was rather meaning if the caller wants ZONE_DEVICE, memory block devices are never an option. So "how the memory is used" not "where memory comes from". add_memory() vs. devm_memremap_pages(). -- Thanks, David / dhildenb
