linux-kernel - Re: [PATCH 1/4] mm/hugetlb: Enable PUD level huge page migration

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Message-ID: <789784ee-4830-753b-5d14-f5c7d90622c4@arm.com>
Date:   Wed, 3 Oct 2018 12:17:52 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     punit.agrawal@....com, will.deacon@....com, Steven.Price@....com,
        catalin.marinas@....com, mhocko@...nel.org,
        mike.kravetz@...cle.com, n-horiguchi@...jp.nec.com
Subject: Re: [PATCH 1/4] mm/hugetlb: Enable PUD level huge page migration



On 03/10/18 12:10, Anshuman Khandual wrote:
> 
> 
> On 10/03/2018 03:52 PM, Suzuki K Poulose wrote:
>>
>>
>> On 02/10/18 13:56, Anshuman Khandual wrote:
>>>
>>>
>>> On 10/02/2018 06:08 PM, Suzuki K Poulose wrote:
>>>> Hi Anshuman
>>>>
>>>> On 02/10/18 13:15, Anshuman Khandual wrote:
>>>>> Architectures like arm64 have PUD level HugeTLB pages for certain configs
>>>>> (1GB huge page is PUD based on ARM64_4K_PAGES base page size) that can be
>>>>> enabled for migration. It can be achieved through checking for PUD_SHIFT
>>>>> order based HugeTLB pages during migration.
>>>>>
>>>>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>>>>> ---
>>>>>     include/linux/hugetlb.h | 3 ++-
>>>>>     1 file changed, 2 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
>>>>> index 6b68e34..9c1b77f 100644
>>>>> --- a/include/linux/hugetlb.h
>>>>> +++ b/include/linux/hugetlb.h
>>>>> @@ -483,7 +483,8 @@ static inline bool hugepage_migration_supported(struct hstate *h)
>>>>>     {
>>>>>     #ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
>>>>>         if ((huge_page_shift(h) == PMD_SHIFT) ||
>>>>> -        (huge_page_shift(h) == PGDIR_SHIFT))
>>>>> +        (huge_page_shift(h) == PUD_SHIFT) ||
>>>>
>>>>
>>>>> +            (huge_page_shift(h) == PGDIR_SHIFT))
>>>>
>>>> nit: Extra Tab ^^.
>>>
>>> The tab is in there when you apply this patch and all three checks are tab separated
>>> in a newline.
>>
>> Well, with the patch applied, at least I can see 2 tabs for the
>> PUD_SHIFT check and 3 tabs for PGDIR_SHIFT check. Which seems
>> inconsistent. Is it just me (my mail client) ?
> 
> I am sorry, you are right. Did not understand your point earlier. Yeah there is
> increasing number of tabs for each new line with a conditional check. Is there
> a problem with this style of indentation ? Though I will be happy to change.

I have been under the idea that all the checks at the same level could
have the same indentation. (i.e, 2 tabs in this case for each). Looks
like there is no rule about it. How about replacing it with a
switch..case  ?

Cheers
Suzuki