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Date:   Thu, 31 Mar 2022 10:50:57 +0200
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Subject: Re: [PATCH v4 1/2] mm: hugetlb_vmemmap: introduce
 ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP
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To:     Muchun Song <songmuchun@bytedance.com>
Cc:     Will Deacon <will@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Bodeddula, Balasubramaniam" <bodeddub@amazon.com>,
        Oscar Salvador <osalvador@suse.de>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        David Rientjes <rientjes@google.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>, james.morse@arm.com,
        Barry Song <21cnbao@gmail.com>,
        LAK <linux-arm-kernel@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        Xiongchun duan <duanxiongchun@bytedance.com>,
        Fam Zheng <fam.zheng@bytedance.com>,
        Muchun Song <smuchun@gmail.com>
References: <20220331065640.5777-1-songmuchun@bytedance.com>
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From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <CAMZfGtV6=n60f2cEWWtFk8Ci1c_JzeNJCmzAs2X6EHZkaXfP6Q@mail.gmail.com>
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On 31.03.22 10:48, Muchun Song wrote:
> On Thu, Mar 31, 2022 at 4:42 PM David Hildenbrand <david@redhat.com> wrote:
>>
>> On 31.03.22 08:56, Muchun Song wrote:
>>> The feature of minimizing overhead of struct page associated with each
>>> HugeTLB page is implemented on x86_64, however, the infrastructure of
>>> this feature is already there, we could easily enable it for other
>>> architectures.  Introduce ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP for other
>>> architectures to be easily enabled.  Just select this config if they
>>> want to enable this feature.
>>>
>>> Suggested-by: Andrew Morton <akpm@linux-foundation.org>
>>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>>> ---
>>>  arch/x86/Kconfig |  1 +
>>>  fs/Kconfig       | 10 +++++++++-
>>>  2 files changed, 10 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>>> index 9f5bd41bf660..e69d42528542 100644
>>> --- a/arch/x86/Kconfig
>>> +++ b/arch/x86/Kconfig
>>> @@ -119,6 +119,7 @@ config X86
>>>       select ARCH_WANTS_DYNAMIC_TASK_STRUCT
>>>       select ARCH_WANTS_NO_INSTR
>>>       select ARCH_WANT_HUGE_PMD_SHARE
>>> +     select ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP      if X86_64
>>>       select ARCH_WANT_LD_ORPHAN_WARN
>>>       select ARCH_WANTS_THP_SWAP              if X86_64
>>>       select ARCH_HAS_PARANOID_L1D_FLUSH
>>> diff --git a/fs/Kconfig b/fs/Kconfig
>>> index 6c7dc1387beb..f6db2af33738 100644
>>> --- a/fs/Kconfig
>>> +++ b/fs/Kconfig
>>> @@ -245,9 +245,17 @@ config HUGETLBFS
>>>  config HUGETLB_PAGE
>>>       def_bool HUGETLBFS
>>>
>>> +#
>>> +# Select this config option from the architecture Kconfig, if it is preferred
>>> +# to enable the feature of minimizing overhead of struct page associated with
>>> +# each HugeTLB page.
>>> +#
>>> +config ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP
>>> +     bool
>>> +
>>>  config HUGETLB_PAGE_FREE_VMEMMAP
>>>       def_bool HUGETLB_PAGE
>>> -     depends on X86_64
>>> +     depends on ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP
>>>       depends on SPARSEMEM_VMEMMAP
>>>
>>>  config HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON
>>
>>
>> I think something like "HUGETLB_OPTIMIZE_VMEMMAP" might be more
>> expressive, but that would imply renaming the existing config knob.
>>
> 
> How about doing a full code cleanup in a separate series in the future?
> 

Yeah.

-- 
Thanks,

David / dhildenb