linux-kernel - Re: [PATCH v3] hugetlb: allow to free gigantic pages regardless of the configuration

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Message-ID: <363365a7-f1ac-5bde-ff7f-bdb137c20628@suse.cz>
Date:   Fri, 15 Feb 2019 17:48:50 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Alexandre Ghiti <alex@...ti.fr>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3] hugetlb: allow to free gigantic pages regardless of
 the configuration

On 2/14/19 8:31 PM, Alexandre Ghiti wrote:
> On systems without CMA or (MEMORY_ISOLATION && COMPACTION) activated but
> that support gigantic pages, boottime reserved gigantic pages can not be
> freed at all. This patch simply enables the possibility to hand back
> those pages to memory allocator.
> 
> This patch also renames:
> 
> - the triplet CMA or (MEMORY_ISOLATION && COMPACTION) into CONTIG_ALLOC,
> and gets rid of all use of it in architecture specific code (and then
> removes ARCH_HAS_GIGANTIC_PAGE config).
> - gigantic_page_supported to make it more accurate: this value being false
> does not mean that the system cannot use gigantic pages, it just means that
> runtime allocation of gigantic pages is not supported, one can still
> allocate boottime gigantic pages if the architecture supports it.
> 
> Signed-off-by: Alexandre Ghiti <alex@...ti.fr>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

Thanks!

...

> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -252,12 +252,17 @@ config MIGRATION
>  	  pages as migration can relocate pages to satisfy a huge page
>  	  allocation instead of reclaiming.
>  
> +

Stray newline? No need to resend, Andrew can fix up.
Ah, he wasn't in To:, adding.

>  config ARCH_ENABLE_HUGEPAGE_MIGRATION
>  	bool
>  
>  config ARCH_ENABLE_THP_MIGRATION
>  	bool
>  
> +config CONTIG_ALLOC
> +	def_bool y
> +	depends on (MEMORY_ISOLATION && COMPACTION) || CMA
> +
>  config PHYS_ADDR_T_64BIT
>  	def_bool 64BIT
>