linux-kernel - Re: [RFC PATCH v2 12/12] mm: make MAX_ORDER a kernel boot time parameter.

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Message-ID: <2e15fc72-5483-b901-5a54-d4a4529d61d9@infradead.org>
Date:   Fri, 12 Aug 2022 18:11:35 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Zi Yan <ziy@...dia.com>, linux-mm@...ck.org
Cc:     David Hildenbrand <david@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Yang Shi <shy828301@...il.com>,
        David Rientjes <rientjes@...gle.com>,
        James Houghton <jthoughton@...gle.com>,
        Mike Rapoport <rppt@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 12/12] mm: make MAX_ORDER a kernel boot time
 parameter.

Hi--

On 8/11/22 16:16, Zi Yan wrote:
> diff --git a/mm/Kconfig b/mm/Kconfig
> index e558f5679707..acccb919d72d 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -455,6 +455,19 @@ config SET_MAX_ORDER
>  	  increase this value. A value of 10 means that the largest free memory
>  	  block is 2^10 pages.
>  
> +config BOOT_TIME_MAX_ORDER
> +	bool "Set maximum order of buddy allocator at boot time"
> +	depends on SPARSEMEM_VMEMMAP && (ARCH_FORCE_MAX_ORDER != 0 || SET_MAX_ORDER != 0)
> +	help
> +	  It enables users to set the maximum order of buddy allocator at system
> +      boot time instead of a static MACRO set at compilation time. Systems with
> +      a lot of memory might want to allocate large pages whereas it is much
> +      less feasible and desirable for systems with less memory. This option
> +      allows different systems to control the largest page they want to
> +      allocate. By default, MAX_ORDER will be set to ARCH_FORCE_MAX_ORDER or
> +      SET_MAX_ORDER, whichever is non-zero, when the boot time parameter is not
> +      set. The maximum of MAX_ORDER is currently limited at 256.

Please make sure that all lines of help text are indented with one tab + 2 spaces,
as specified in Documentation/process/coding-style.rst.

Thanks.
-- 
~Randy