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authorKalesh Singh <kaleshsingh@google.com>2020-10-14 00:53:07 +0000
committerWill Deacon <will@kernel.org>2020-10-15 11:27:28 +0100
commit45544eee96065cf183fbb937fe1f45a172b06f4e (patch)
tree93377a892650c7f5d3fe9967c673a2e6fb076eb2 /arch/arm64
parent7bc1a0f9e1765830e945669c99c59c35cf9bca82 (diff)
arm64: mremap speedup - Enable HAVE_MOVE_PMD
HAVE_MOVE_PMD enables remapping pages at the PMD level if both the source and destination addresses are PMD-aligned. HAVE_MOVE_PMD is already enabled on x86. The original patch [1] that introduced this config did not enable it on arm64 at the time because of performance issues with flushing the TLB on every PMD move. These issues have since been addressed in more recent releases with improvements to the arm64 TLB invalidation and core mmu_gather code as Will Deacon mentioned in [2]. >From the data below, it can be inferred that there is approximately 8x improvement in performance when HAVE_MOVE_PMD is enabled on arm64. --------- Test Results ---------- The following results were obtained on an arm64 device running a 5.4 kernel, by remapping a PMD-aligned, 1GB sized region to a PMD-aligned destination. The results from 10 iterations of the test are given below. All times are in nanoseconds. Control HAVE_MOVE_PMD 9220833 1247761 9002552 1219896 9254115 1094792 8725885 1227760 9308646 1043698 9001667 1101771 8793385 1159896 8774636 1143594 9553125 1025833 9374010 1078125 9100885.4 1134312.6 <-- Mean Time in nanoseconds Total mremap time for a 1GB sized PMD-aligned region drops from ~9.1 milliseconds to ~1.1 milliseconds. (~8x speedup). [1] https://lore.kernel.org/r/20181108181201.88826-3-joelaf@google.com [2] https://www.mail-archive.com/linuxppc-dev@lists.ozlabs.org/msg140837.html Signed-off-by: Kalesh Singh <kaleshsingh@google.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: https://lore.kernel.org/r/20201014005320.2233162-3-kaleshsingh@google.com Link: https://lore.kernel.org/kvmarm/20181029102840.GC13965@arm.com/ Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/Kconfig1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 43091f439e4e..02e1a868d570 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -122,6 +122,7 @@ config ARM64
select GENERIC_VDSO_TIME_NS
select HANDLE_DOMAIN_IRQ
select HARDIRQS_SW_RESEND
+ select HAVE_MOVE_PMD
select HAVE_PCI
select HAVE_ACPI_APEI if (ACPI && EFI)
select HAVE_ALIGNED_STRUCT_PAGE if SLUB