Re: [PATCH -next V2] riscv: mm: hugetlb: Enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP

[Andrew Jones <ajones@ventanamicro.com>]

On Fri, Jan 27, 2023 at 12:04:21AM -0500, guoren@kernel.org wrote:
> From: Guo Ren <guoren@linux.alibaba.com>
> 
> Add HVO support for RISC-V; see commit 6be24bed9da3 ("mm: hugetlb:
> introduce a new config HUGETLB_PAGE_FREE_VMEMMAP").

I found Documentation/mm/vmemmap_dedup.rst even more enlightening
about HVO than the commit message of 6be24bed9da3.

> This patch is
> similar to commit 1e63ac088f20 ("arm64: mm: hugetlb: enable
> HUGETLB_PAGE_FREE_VMEMMAP for arm64"), and riscv's motivation is the
> same as arm64. The current riscv was ready to enable HVO after fixup,
> ref commit d33deda095d3 ("riscv/mm: hugepage's PG_dcache_clean flag
> is only set in head page").
> 
> The HugeTLB VmemmapvOptimization (HVO) defaults to off in Kconfig.
> 
> Here is the riscv test log:
> cat /proc/sys/vm/hugetlb_optimize_vmemmap
> echo 8 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
> mount -t hugetlbfs none test/ -o pagesize=2048k
> <Try some simple hugetlb test in test dir, no problem found.>
> 
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Link: https://lore.kernel.org/linux-riscv/1F5AF29D-708A-483B-A29F-CAEE6F554866@linux.dev/
> Acked-by: Muchun Song <songmuchun@bytedance.com>
> ---
> Changelog:
> V2:
>  - Optimize the commit log
>  - Remove riscv page compound_head fixup which has been merged.
>  - Rebase on riscv for-next (20230127)
>  - Add HVO author's acked-by
> 
> V1:
> https://lore.kernel.org/linux-riscv/20221023133205.3493564-1-guoren@kernel.org/
> ---
>  arch/riscv/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index e2b656043abf..949974a38a41 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -46,6 +46,7 @@ config RISCV
>  	select ARCH_WANT_FRAME_POINTERS
>  	select ARCH_WANT_GENERAL_HUGETLB
>  	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
> +	select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
>  	select ARCH_WANTS_THP_SWAP if HAVE_ARCH_TRANSPARENT_HUGEPAGE
>  	select BINFMT_FLAT_NO_DATA_START_OFFSET if !MMU
>  	select BUILDTIME_TABLE_SORT if MMU
> -- 
> 2.36.1
>

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

Thanks,
drew

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