On 2022/8/27 10:48, Muchun Song wrote: > > >> On Aug 27, 2022, at 10:27, Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote: >> >> On 2022/8/27 9:47, Muchun Song wrote: >>> >>> >>>> On Aug 26, 2022, at 17:24, Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote: >>>> >>>> We can avoid unneeded WRITE_ONCE() overhead by using LIST_HEAD() to define >>>> a list head. >>> >>> IIUC, the overhead doesn’t change. Right? >> >> I think the overhead is changed. LIST_HEAD is initialized without using WRITE_ONCE(): > > I think there is no special difference with "WRITE_ONCE(var, 0)" vs "var = 0” in It's not write var to 0 indeed. But there seems are no special difference. > assembly code. Both code of line will be compiled to a mov or movq instruction. > I didn’t confirm if the assembly code is different (I tend to think it is similar). > Just some analysis from me. I checked the generated code in x86, they're almost same. And in aarch64, there's difference between one "stp" instruction vs two "str" instruction. So I think you're right. Thanks for pointing this out. I should tweak the commit log in next version. Thanks a lot, Miaohe Lin
