Commit 53fa117b authored Sep 09, 2020 by Anshuman Khandual Committed by Will Deacon Sep 11, 2020

arm64/mm: Enable THP migration



In certain page migration situations, a THP page can be migrated without
being split into it's constituent subpages. This saves time required to
split a THP and put it back together when required. But it also saves an
wider address range translation covered by a single TLB entry, reducing
future page fault costs.

A previous patch changed platform THP helpers per generic memory semantics,
clearing the path for THP migration support. This adds two more THP helpers
required to create PMD migration swap entries. Now enable THP migration via
ARCH_ENABLE_THP_MIGRATION.

Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Suzuki Poulose <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Link: https://lore.kernel.org/r/1599627183-14453-3-git-send-email-anshuman.khandual@arm.com


Signed-off-by: Will Deacon <will@kernel.org>

parent b65399f6

arch/arm64/Kconfig

+4 −0

Original line number	Diff line number	Diff line
		@@ -1876,6 +1876,10 @@ config ARCH_ENABLE_HUGEPAGE_MIGRATION
		def_bool y
		depends on HUGETLB_PAGE && MIGRATION

		config ARCH_ENABLE_THP_MIGRATION
		def_bool y
		depends on TRANSPARENT_HUGEPAGE

		menu "Power management options"

		source "kernel/power/Kconfig"

arch/arm64/include/asm/pgtable.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -875,6 +875,11 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
		#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
		#define __swp_entry_to_pte(swp) ((pte_t) { (swp).val })

		#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
		#define __pmd_to_swp_entry(pmd) ((swp_entry_t) { pmd_val(pmd) })
		#define __swp_entry_to_pmd(swp) __pmd((swp).val)
		#endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */

		/*
		* Ensure that there are not more swap files than can be encoded in the kernel
		* PTEs.

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