Re: [PATCH v2 5/5] mm/hugetlb: avoid calculating fault_mutex_hash in truncate_op case

From: Mike Kravetz
Date: Tue Mar 16 2021 - 20:32:17 EST

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@xxxxxxxxxx>
>>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>>> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
>>> ---
>>> 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