linux-kernel - Re: [RFC PATCH 20/24] mm/hugetlb: Add a kernel parameter hugetlb_free

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Message-ID: <defc8d4f-b143-d4ae-f609-fd22624aafc3@infradead.org>
Date:   Tue, 15 Sep 2020 19:10:59 -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 20/24] mm/hugetlb: Add a kernel parameter
 hugetlb_free_vmemmap

Hi,
Please see comments below.

On 9/15/20 5:59 AM, Muchun Song wrote:
> Add a kernel parameter hugetlb_free_vmemmap to disable the feature of
> freeing unused vmemmap pages associated with each hugetlb page on boot.
> 
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> ---
>  .../admin-guide/kernel-parameters.txt         |  9 ++++++++
>  Documentation/admin-guide/mm/hugetlbpage.rst  |  3 +++
>  mm/hugetlb.c                                  | 23 +++++++++++++++++++
>  3 files changed, 35 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 5debfe238027..69d18ef6f66b 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1551,6 +1551,15 @@
>  			Documentation/admin-guide/mm/hugetlbpage.rst.
>  			Format: size[KMG]
>  
> +	hugetlb_free_vmemmap=
> +			[KNL] When CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is set,
> +			this disables freeing unused vmemmap pages associated

			this controls

> +			each HugeTLB page.

			with each HugeTLB page.

> +			Format: { on (default) | off }
> +
> +			on:  enable the feature
> +			off: dosable the feature

			     disable

> +
>  	hung_task_panic=
>  			[KNL] Should the hung task detector generate panics.
>  			Format: 0 | 1
> diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
> index f7b1c7462991..7d6129ee97dd 100644
> --- a/Documentation/admin-guide/mm/hugetlbpage.rst
> +++ b/Documentation/admin-guide/mm/hugetlbpage.rst
> @@ -145,6 +145,9 @@ default_hugepagesz
>  
>  	will all result in 256 2M huge pages being allocated.  Valid default
>  	huge page size is architecture dependent.

insert blank line here.

> +hugetlb_free_vmemmap
> +	When CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is set, this disables freeing
> +	unused vmemmap pages associated each HugeTLB page.
>  
>  When multiple huge page sizes are supported, ``/proc/sys/vm/nr_hugepages``
>  indicates the current number of pre-allocated huge pages of the default size.


-- 
~Randy