linux-kernel - Re: [PATCH v4 1/2] mm: hugetlb_vmemmap: introduce ARCH_WANT_HUGETLB_PAGE_FREE

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Date:   Thu, 31 Mar 2022 16:48:33 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Bodeddula, Balasubramaniam" <bodeddub@...zon.com>,
        Oscar Salvador <osalvador@...e.de>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        David Rientjes <rientjes@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>, james.morse@....com,
        Barry Song <21cnbao@...il.com>,
        LAK <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Xiongchun duan <duanxiongchun@...edance.com>,
        Fam Zheng <fam.zheng@...edance.com>,
        Muchun Song <smuchun@...il.com>
Subject: Re: [PATCH v4 1/2] mm: hugetlb_vmemmap: introduce ARCH_WANT_HUGETLB_PAGE_FREE_VMEMMAP

On Thu, Mar 31, 2022 at 4:42 PM David Hildenbrand <david@...hat.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@...ux-foundation.org>
> > Signed-off-by: Muchun Song <songmuchun@...edance.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?