Commit 0388f9c7 authored Nov 24, 2020 by Will Deacon

arm64: mm: Implement arch_wants_old_prefaulted_pte()



On CPUs with hardware AF/DBM, initialising prefaulted PTEs as 'old'
improves vmscan behaviour and does not appear to introduce any overhead
elsewhere.

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>

parent 46bdb427

arch/arm64/include/asm/pgtable.h

+11 −1

Original line number	Diff line number	Diff line
		@@ -982,6 +982,16 @@ static inline bool arch_faults_on_old_pte(void)
		}
		#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__ */

		#endif /* __ASM_PGTABLE_H */