linux-kernel - Re: [RFC PATCH 03/24] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE

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Date:   Tue, 15 Sep 2020 19:13:46 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Muchun Song <songmuchun@...edance.com>, corbet@....net,
        mike.kravetz@...cle.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
        paulmck@...nel.org, mchehab+huawei@...nel.org,
        pawan.kumar.gupta@...ux.intel.com, oneukum@...e.com,
        anshuman.khandual@....com, jroedel@...e.de, almasrymina@...gle.com,
        rientjes@...gle.com
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org
Subject: Re: [RFC PATCH 03/24] mm/hugetlb: Introduce a new config
 HUGETLB_PAGE_FREE_VMEMMAP

On 9/15/20 5:59 AM, Muchun Song wrote:
> The purpose of introducing HUGETLB_PAGE_FREE_VMEMMAP is to configure
> whether to enable the feature of freeing unused vmemmap associated
> with HugeTLB pages.
> 
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> ---
>  fs/Kconfig | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 976e8b9033c4..61e9c08096ca 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -245,6 +245,21 @@ config HUGETLBFS
>  config HUGETLB_PAGE
>  	def_bool HUGETLBFS
>  
> +config HUGETLB_PAGE_FREE_VMEMMAP
> +	bool "Free unused vmemmap associated with HugeTLB pages"
> +	default n
> +	depends on HUGETLB_PAGE
> +	depends on SPARSEMEM_VMEMMAP
> +	depends on HAVE_BOOTMEM_INFO_NODE
> +	help
> +	  There are many struct page structure associated with each HugeTLB

	                             structures

> +	  page. But we only use a few struct page structure. In this case,

	                                          structures.

> +	  it waste some memory. It is better to free the unused struct page

	  it wastes

> +	  structures to buddy system which can save some memory. For
> +	  architectures that support it, say Y here.
> +
> +	  If unsure, say N.
> +
>  config MEMFD_CREATE
>  	def_bool TMPFS || HUGETLBFS
>  
> 


-- 
~Randy