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

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Date:   Sat, 19 Jan 2019 23:57:57 +0000
From:   Will Deacon <will.deacon@....com>
To:     Alexandre Ghiti <aghiti@...em.com>
Cc:     Catalin Marinas <catalin.marinas@....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,
        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,
        hch@...radead.org, linux-riscv@...ts.infradead.org,
        Alexandre Ghiti <alex@...ti.fr>
Subject: Re: [PATCH] hugetlb: allow to free gigantic pages regardless of the
 configuration

On Thu, Jan 17, 2019 at 06:39:53PM +0000, Alexandre Ghiti wrote:
> From: Alexandre Ghiti <alex@...ti.fr>
> 
> 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 patchs simply enables the possibility to hand back
> those pages to memory allocator.
> 
> This commit then renames gigantic_page_supported and
> ARCH_HAS_GIGANTIC_PAGE to make them more accurate. Indeed, those values
> 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>
> ---
> 
> - Compiled on all architectures
> - Tested on riscv architecture
> 
>  arch/arm64/Kconfig                           |  2 +-
>  arch/arm64/include/asm/hugetlb.h             |  7 +++--

The arm64 bits look straightforward enough to me...

Acked-by: Will Deacon <will.deacon@....com>

Will