On 22.08.2018 09:50, Oscar Salvador wrote: > On Tue, Aug 21, 2018 at 03:17:10PM +0200, David Hildenbrand wrote: >>> add_device_memory is in charge of >> >> I wouldn't use the terminology of onlining/offlining here. That applies >> rather to memory that is exposed to the rest of the system (e.g. buddy >> allocator, has underlying memory block devices). I guess it is rather a >> pure setup/teardown of that device memory. > > Hi David, > > I am not sure if you are referring to: > > " > a) calling either arch_add_memory() or add_pages(), depending on whether > we want a linear mapping > b) online the memory sections that correspond to the pfn range > c) calling move_pfn_range_to_zone() being zone ZONE_DEVICE to > expand zone/pgdat spanned pages and initialize its pages > " > > Well, that is partialy true. > I mean, in order to make this work, we need to offline/online the memory > sections, because shrink_pages will rely on that from now on. > Is what we do when online/offline pages, but since device memory > does not go through the "official" channels, we need to do it there > as well. > > Sure I can use another terminology, but since that is what > offline/online_mem_sections do, I just came up with that. > Okay, got it, so it is basically "mark the sections as online/offline". >> I would really like to see the mem_hotplug_begin/end also getting moved >> inside add_device_memory()/del_device_memory(). (just like for >> add/remove_memory) >> >> I wonder if kasan_ stuff actually requires this lock, or if it could >> also be somehow moved inside add_device_memory/del_device_memory. > > Yes, that was my first approach, but then I saw that the kasan stuff is being > handled whithin those locks, so I was not sure and I backed off leaving the > mem_hotplug_begin/end where they were. > > Maybe Jerome can shed some light and, and we can just handle the kasan stuff > out of the locks. > >> Maybe shorten that a bit >> >> "HMM/devm memory does not have IORESOURCE_SYSTEM_RAM set. They use >> devm_request_mem_region/devm_release_mem_region to add/release a >> resource. Just back off here." > > Uhm, fair enough. > >> Any reason for these indirections? > > I wanted to hide the internals in the memory_hotplug code. > I thought about removing them, but I finally left them. > If people think that we are better off without them, I can just > remove them. I don't see a need for that. (everyone following the functions has to go via one indirection that just passes on parameters). It is also not done for other functions (a.g. add_memory) > >> I guess for readability, this patch could be split up into several >> patches. E.g. factoring out of add_device_memory/del_device_memory, >> release_mem_region_adjustable change ... > > Yes, really true. > But I wanted first to gather feedback mainly from HMM/devm people to see > if they saw an outright bug within the series because I am not so > familiar with that part of the code. > > Feedback from Jerome/Dan will be appreciate as well to see if this is a good > direction. Yes, they probably know best how this all fits together. > > But you are right, in the end, this will have to be slipt up into several > parts to ease the review. > > Thanks for reviewing this David! > I will try to address your concerns. > > Thanks > -- Thanks, David / dhildenb
