On 2024/2/28 09:54, Sergey Senozhatsky wrote: > On (24/02/27 16:16), Chengming Zhou wrote: >> 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). > > Correct. > >>> 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. > > Right, that's what I was talking about. > >>>> 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? > > Yes, thanks. I think separating handle and object header in the commit > message will be helpful. Right, I will improve the commit message and send v2. Thanks!
