2024년 4월 19일 (금) 오전 10:46, DaeRo Lee <skseofh@xxxxxxxxx>님이 작성: > > 2024년 4월 19일 (금) 오전 3:04, Mike Rapoport <rppt@xxxxxxxxxx>님이 작성: > > > > On Thu, Apr 18, 2024 at 11:54:15PM +0900, DaeRo Lee wrote: > > > 2024년 4월 17일 (수) 오후 3:03, Mike Rapoport <rppt@xxxxxxxxxx>님이 작성: > > > > > > > > On Tue, Apr 16, 2024 at 09:06:35PM +0900, skseofh@xxxxxxxxx wrote: > > > > > From: Daero Lee <daero_le.lee@xxxxxxxxxxx> > > > > > > > > > > Like reserved-memory with the 'no-map' property and only 'size' property > > > > > (w/o 'reg' property), there are memory regions need to be allocated in > > > > > memblock.memory marked with the MEMBLOCK_NOMAP flag, but should not be > > > > > allocated in memblock.reserved. > > > > > > > > This still does not explain why you need such regions. > > > > > > > > As Wei Yang explained, memblock does not allocate memory from > > > > memblock.reserved. The memblock.reserved array represents memory that is in > > > > use by firmware or by early kernel allocations and cannot be freed to page > > > > allocator. > > > Thank you for your comments. I used the wrong word. > > > When I use 'allocate', I mean that the region 'adds' to the memblock.reserved. > > > > > > > > > > > If you have a region that's _NOMAP in memblock.memory and is absent in > > > > memblock.reserved it will not be mapped by the kernel page tables, but it > > > > will be considered as free memory by the core mm. > > > > > > > > Is this really what you want? > > > If my understanding is right, before freeing (memory && !reserved) > > > area, we marked the memblock.reserved regions and memblock.memory > > > regions with no-map flag. And when we free (memory && !reserved) area, > > > we skip the memblock.memory regions with no-map(see > > > should_skip_region). So, I think that the memory regions with no-map > > > flag will not be considered as free memory. > > > > You are right here. > > > > But I still don't understand *why* do you want to change the way > > early_init_dt_alloc_reserved_memory_arch() works. > > In memmap_init_reserved_pages, we mark memblock.reserved as > PageReserved first and mark the memblock.reserved with nomap flag > also. Sorry. This is my mistake. 'memblock.memory with nomap flag' is right. > -> Isn't this duplicated work? (If we add no-map region to > memblock.reserved 'and' mark in memblock.memory..) > So, I think that for the no-map region, we don't need to add to the > memblock.reserved. > This is what we do now in early_init_dt_reserve_memory. the nomap > region is not added to the memblock.reserved. > > In early_init_dt_alloc_reserved_memory_arch, if 'nomap' is true, we > mark the memblock.memory region as _NOMAP. And if the return value > 'err' is not zero(which is '-ENOMEM' from memblock_isolate_range), we > free the region. > - 'nomap' is true -> memblock_mark_nomap : success -> not free the region > > : fail -> free the region > And it can be said that we add the region to the memblock.reserved > using memblock_phys_alloc_range and if the region is nomap, then we > can free the region from memblock.reserved. But is it necessary to add > it to memblock.reserved? We just need the region in memblock.memory to > mark nomap. > > So, here is what I think: > - reserved-memory w/ nomap region -> mark only to memblock.memory > - reserved-memory w/o nomap region -> add to the memblock.reserved > > Regards, > DaeRo Lee
