On 2024/2/27 15:52, Sergey Senozhatsky wrote: > On (24/02/27 03:00), chengming.zhou@xxxxxxxxx wrote: >> >> We only need to save the position (pfn + obj_idx) in the handle, don't >> need to save tag bit in handle. So one more bit can be used as obj_idx. > > [..] > >> mm/zsmalloc: don't need to save tag bit in handle > > Does this mean "don't need to reserve LSB for tag"? The head of object still need to reverve LSB, to save (handle | OBJ_ALLOCATED_TAG), only the handle doesn't need to reserve LSB, which save (pfn | obj_idx). > We still save allocated tag in the handle, that's what > > handle |= OBJ_ALLOCATED_TAG; Yes, this result will be saved in the head of each allocated object. > > does. > >> Actually, the tag bit is only useful in zspage's memory space, to tell >> if an object is allocated or not. > > I'm not completely sure if I follow this sentence. What I mean is that only the head of each allocated object need to reverve LSB, which is used to check if allocated or not. handle address -> handle (pfn + obj_idx) -> object: (handle | tag), real_object start I'm not sure if this makes it clearer? Thanks.
