From: Muchun Song <muchun.song@linux.dev>
To: Miaohe Lin <linmiaohe@huawei.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
mike.kravetz@oracle.com, Muchun Song <songmuchun@bytedance.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 03/10] hugetlb: Use LIST_HEAD() to define a list head
Date: Sat, 27 Aug 2022 10:48:34 +0800 [thread overview]
Message-ID: <83DBE074-0B63-4CB2-9BD2-65967977B69C@linux.dev> (raw)
In-Reply-To: <bb05153c-29a9-b77e-0815-506309da6da0@huawei.com>
> 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
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.
>
> #define LIST_HEAD_INIT(name) { &(name), &(name) }
>
> #define LIST_HEAD(name) \
> struct list_head name = LIST_HEAD_INIT(name)
>
> while INIT_LIST_HEAD has:
>
> static inline void INIT_LIST_HEAD(struct list_head *list)
> {
> WRITE_ONCE(list->next, list);
> WRITE_ONCE(list->prev, list);
> }
>
> Or am I miss something?
>
>>
>> I’m fine with your changes.
>>
>> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
>
> Many thanks for your review and comment. :)
>
> Thanks,
> Miaohe Lin
>
next prev parent reply other threads:[~2022-08-27 2:48 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-26 9:24 [PATCH 00/10] A few cleanup patches for hugetlb Miaohe Lin
2022-08-26 9:24 ` [PATCH 01/10] hugetlb: make hugetlb_cma_check() static Miaohe Lin
2022-08-27 1:40 ` Muchun Song
2022-08-26 9:24 ` [PATCH 02/10] hugetlb: Use helper macro SZ_1K Miaohe Lin
2022-08-27 1:40 ` Muchun Song
2022-08-26 9:24 ` [PATCH 03/10] hugetlb: Use LIST_HEAD() to define a list head Miaohe Lin
2022-08-27 1:47 ` Muchun Song
2022-08-27 2:27 ` Miaohe Lin
2022-08-27 2:48 ` Muchun Song [this message]
2022-08-27 6:38 ` Miaohe Lin
2022-08-26 9:24 ` [PATCH 04/10] hugetlb: Use sizeof() to get the array size Miaohe Lin
2022-08-27 1:43 ` Muchun Song
2022-08-26 9:24 ` [PATCH 05/10] hugetlb: Use helper {huge_pte|pmd}_lock() Miaohe Lin
2022-08-27 1:48 ` Muchun Song
2022-08-26 9:24 ` [PATCH 06/10] hugetlb: pass NULL to kobj_to_hstate() if nid is unused Miaohe Lin
2022-08-27 1:49 ` Muchun Song
2022-08-26 9:24 ` [PATCH 07/10] hugetlb: kill hugetlbfs_pagecache_page() Miaohe Lin
2022-08-27 1:52 ` Muchun Song
2022-08-26 9:24 ` [PATCH 08/10] hugetlb: remove unneeded SetHPageVmemmapOptimized() Miaohe Lin
2022-08-27 1:35 ` Muchun Song
2022-08-27 2:18 ` Miaohe Lin
2022-08-27 2:56 ` Muchun Song
2022-08-26 9:24 ` [PATCH 09/10] hugetlb: remove meaningless BUG_ON(huge_pte_none()) Miaohe Lin
2022-08-27 2:03 ` Muchun Song
2022-08-26 9:24 ` [PATCH 10/10] hugetlb: make hugetlb selects SYSFS if !SYSCTL Miaohe Lin
2022-08-27 1:59 ` Muchun Song
2022-08-27 2:34 ` Miaohe Lin
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