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

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Date:   Tue, 16 Mar 2021 17:27:45 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Miaohe Lin <linmiaohe@...wei.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 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.

All the cleanup patches in this series should be good to go.
-- 
Mike Kravetz