lkml.org 
[lkml]   [2022]   [Aug]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 03/10] hugetlb: Use LIST_HEAD() to define a list head
From
Date
On 2022/8/27 10:48, Muchun Song wrote:
>
>
>> On Aug 27, 2022, at 10:27, Miaohe Lin <linmiaohe@huawei.com> wrote:
>>
>> On 2022/8/27 9:47, Muchun Song wrote:
>>>
>>>
>>>> On Aug 26, 2022, at 17:24, Miaohe Lin <linmiaohe@huawei.com> 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

\
 
 \ /
  Last update: 2022-08-27 08:39    [W:0.053 / U:0.080 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site