linux-kernel - Re: [PATCH 3/6] mm: hugetlb_vmemmap: introduce the name HVO

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Date:   Tue, 14 Jun 2022 11:15:49 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     mike.kravetz@...cle.com, akpm@...ux-foundation.org, corbet@....net,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH 3/6] mm: hugetlb_vmemmap: introduce the name HVO

On Mon, Jun 13, 2022 at 05:39:59PM +0200, David Hildenbrand wrote:
> On 13.06.22 08:35, Muchun Song wrote:
> > It it inconvenient to mention the feature of optimizing vmemmap pages associated
> > with HugeTLB pages when communicating with others since there is no specific or
> > abbreviated name for it when it is first introduced.  Let us give it a name HVO
> > (HugeTLB Vmemmap Optimization) from now.
> > 
> > This commit also updates the document about "hugetlb_free_vmemmap" by the way
> > discussed in thread [1].
> > 
> > Link: https://lore.kernel.org/all/21aae898-d54d-cc4b-a11f-1bb7fddcfffa@redhat.com/ [1]
> > Signed-off-by: Muchun Song <songmuchun@...edance.com>
> > ---
> >  Documentation/admin-guide/kernel-parameters.txt |  7 ++++---
> >  Documentation/admin-guide/mm/hugetlbpage.rst    |  3 +--
> >  Documentation/admin-guide/sysctl/vm.rst         |  3 +--
> >  fs/Kconfig                                      | 13 ++++++-------
> >  mm/hugetlb_vmemmap.c                            |  8 ++++----
> >  mm/hugetlb_vmemmap.h                            |  4 ++--
> >  6 files changed, 18 insertions(+), 20 deletions(-)
> > 
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 391b43fee93e..7539553b3fb0 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -1725,12 +1725,13 @@
> >  	hugetlb_free_vmemmap=
> >  			[KNL] Reguires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
> >  			enabled.
> > +			Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
> >  			Allows heavy hugetlb users to free up some more
> >  			memory (7 * PAGE_SIZE for each 2MB hugetlb page).
> > -			Format: { [oO][Nn]/Y/y/1 | [oO][Ff]/N/n/0 (default) }
> > +			Format: { on | off (default) }
> >  
> > -			[oO][Nn]/Y/y/1: enable the feature
> > -			[oO][Ff]/N/n/0: disable the feature
> > +			on: enable HVO
> > +			off: disable HVO
> >  
> >  			Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
> >  			the default is on.
> > diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
> > index a90330d0a837..64e0d5c512e7 100644
> > --- a/Documentation/admin-guide/mm/hugetlbpage.rst
> > +++ b/Documentation/admin-guide/mm/hugetlbpage.rst
> > @@ -164,8 +164,7 @@ default_hugepagesz
> >  	will all result in 256 2M huge pages being allocated.  Valid default
> >  	huge page size is architecture dependent.
> >  hugetlb_free_vmemmap
> > -	When CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is set, this enables optimizing
> > -	unused vmemmap pages associated with each HugeTLB page.
> > +	When CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is set, this enables HVO.
> 
> Heh, it would be convenient to call this
> 
> CONFIG_HUGETLB_PAGE_VMEMMAP_OPTIMIZATION (HVO) then.
>

Thanks for pointing it out. I would take Mike's suggestion. I would change to:

  When CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is set this enables
  HugeTLB Vmemmap Optimization (HVO).

Thanks.