linux-kernel - Re: [RFC PATCH v2 07/47] hugetlb: add CONFIG_HUGETLB_HIGH_GRANULARITY

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Message-ID: <Y5O8Eewl0v6CSmt6@monkey>
Date:   Fri, 9 Dec 2022 14:52:01 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     James Houghton <jthoughton@...gle.com>
Cc:     Muchun Song <songmuchun@...edance.com>,
        Peter Xu <peterx@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Zach O'Keefe <zokeefe@...gle.com>,
        Manish Mishra <manish.mishra@...anix.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 07/47] hugetlb: add
 CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING

On 10/21/22 16:36, James Houghton wrote:
> This adds the Kconfig to enable or disable high-granularity mapping.
> Each architecture must explicitly opt-in to it (via
> ARCH_WANT_HUGETLB_HIGH_GRANULARITY_MAPPING), but when opted in, HGM will
> be enabled by default if HUGETLB_PAGE is enabled.
> 
> Signed-off-by: James Houghton <jthoughton@...gle.com>
> ---
>  fs/Kconfig | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 2685a4d0d353..ce2567946016 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -267,6 +267,13 @@ config HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON
>  	  enable HVO by default. It can be disabled via hugetlb_free_vmemmap=off
>  	  (boot command line) or hugetlb_optimize_vmemmap (sysctl).
>  
> +config ARCH_WANT_HUGETLB_HIGH_GRANULARITY_MAPPING
> +	bool
> +
> +config HUGETLB_HIGH_GRANULARITY_MAPPING
> +	def_bool HUGETLB_PAGE
> +	depends on ARCH_WANT_HUGETLB_HIGH_GRANULARITY_MAPPING

Might also need to make this depend on CONFIG_ARCH_WANT_HUGE_PMD_SHARE
as the vma local allocation will only happen in this case.

-- 
Mike Kravetz

> +
>  config MEMFD_CREATE
>  	def_bool TMPFS || HUGETLBFS
>  
> -- 
> 2.38.0.135.g90850a2211-goog
>