Re: [PATCH] arm64/mm: Drop THP conditionality from FORCE_MAX_ZONEORDER
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2021-03-01 15:18:59
Also in:
lkml
On Mon, Mar 01, 2021 at 04:55:14PM +0530, Anshuman Khandual wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 9cd33c7be429..d4690326274a 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig@@ -1156,8 +1156,8 @@ config XEN config FORCE_MAX_ZONEORDER int - default "14" if (ARM64_64K_PAGES && TRANSPARENT_HUGEPAGE) - default "12" if (ARM64_16K_PAGES && TRANSPARENT_HUGEPAGE) + default "14" if ARM64_64K_PAGES + default "12" if ARM64_16K_PAGES default "11" help The kernel memory allocator divides physically contiguous memory
I think this makes sense. The original "14" was added by Steve C in
commit d03bb1455f3a ("ARM64: mm: Raise MAX_ORDER for 64KB pages and
THP.") back in 3.11. It looks like hugetlbfs (and the HUGETLB_PAGE_ORDER
definition) was added in the same kernel but we somehow missed the
!TRANSPARENT_HUGEPAGE case and smaller page order. The warning in
__fragmentation_index() was added much later in 4.14.
Anyway, the patch looks fine to me, we could apply it to some past
stable kernels:
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
An alternative would have be to add a dependency on both
TRANSPARENT_HUGEPAGE and HUGETLB_PAGE but I'm not sure it's worth it.
--
Catalin
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