Messages in this thread Patch in this message | | | From | Will Deacon <> | Subject | [PATCH v2 3/3] arm64: mm: Implement arch_wants_old_prefaulted_pte() | Date | Fri, 8 Jan 2021 17:15:17 +0000 |
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On CPUs with hardware AF/DBM, initialising prefaulted PTEs as 'old' improves vmscan behaviour and does not appear to introduce any overhead.
Implement arch_wants_old_prefaulted_pte() to return 'true' if we detect hardware access flag support at runtime. This can be extended in future based on MIDR matching if necessary.
Cc: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will@kernel.org> --- arch/arm64/include/asm/pgtable.h | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 501562793ce2..e17b96d0e4b5 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -980,7 +980,17 @@ static inline bool arch_faults_on_old_pte(void) return !cpu_has_hw_af(); } -#define arch_faults_on_old_pte arch_faults_on_old_pte +#define arch_faults_on_old_pte arch_faults_on_old_pte + +/* + * Experimentally, it's cheap to set the access flag in hardware and we + * benefit from prefaulting mappings as 'old' to start with. + */ +static inline bool arch_wants_old_prefaulted_pte(void) +{ + return !arch_faults_on_old_pte(); +} +#define arch_wants_old_prefaulted_pte arch_wants_old_prefaulted_pte #endif /* !__ASSEMBLY__ */ -- 2.29.2.729.g45daf8777d-goog
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