linux-kernel - Re: [PATCH v2 5/5] mm/hugetlb: avoid calculating fault_mutex_hash in truncate

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Message-ID: <fb988ad4-8a1b-14ef-ed94-7658b2af8ab2@huawei.com>
Date:   Wed, 17 Mar 2021 09:44:50 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>, <akpm@...ux-foundation.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH v2 5/5] mm/hugetlb: avoid calculating fault_mutex_hash in
 truncate_op case

On 2021/3/17 8:27, Mike Kravetz wrote:
> On 3/15/21 11:49 PM, Miaohe Lin wrote:
>> On 2021/3/16 11:07, Mike Kravetz wrote:
>>> On 3/15/21 7:27 PM, Miaohe Lin wrote:
>>>> The fault_mutex hashing overhead can be avoided in truncate_op case
>>>> because page faults can not race with truncation in this routine.  So
>>>> calculate hash for fault_mutex only in !truncate_op case to save some cpu
>>>> cycles.
>>>>
>>>> Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
>>>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>>>> Cc: Mike Kravetz <mike.kravetz@...cle.com>
>>>> ---
>>>> v1->v2:
>>>> remove unnecessary initialization for variable hash
>>>> collect Reviewed-by tag from Mike Kravetz
>>>
>>> My apologies for not replying sooner and any misunderstanding from my
>>> previous comments.
>>>
>>
>> That's all right.
>>
>>> If the compiler is going to produce a warning because the variable is
>>> not initialized, then we will need to keep the initialization.
>>> Otherwise, this will show up as a build regression.  Ideally, there
>>> would be a modifier which could be used to tell the compiler the
>>> variable will used.  I do not know if such a modifier exists.
>>>
>>
>> I do not know if such a modifier exists too. But maybe not all compilers are intelligent
>> enough to not produce a warning. It would be safe to keep the initialization...
>>
>>> The patch can not produce a new warning.  So, if you need to initialize
>>
>> So just drop this version of the patch? Or should I send a new version with your Reviewed-by tag and
>> keep the initialization?
>>
> 
> Yes, drop this version of the patch.  You can add my Reviewed-by to the
> previous version that included the initialization and resend.
> 

Will do. Many thanks. :)

> All the cleanup patches in this series should be good to go.
>