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Subject[PATCH v2 0/6] Speed up mremap on large regions
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This version 2 of the mremap speed up patches previously posted at:
https://lore.kernel.org/r/20200930222130.4175584-1-kaleshsingh@google.com

mremap time can be optimized by moving entries at the PMD/PUD level if
the source and destination addresses are PMD/PUD-aligned and
PMD/PUD-sized. Enable moving at the PMD and PUD levels on arm64 and
x86. Other architectures where this type of move is supported and known to
be safe can also opt-in to these optimizations by enabling HAVE_MOVE_PMD
and HAVE_MOVE_PUD.

Observed Performance Improvements for remapping a PUD-aligned 1GB-sized
region on x86 and arm64:

- HAVE_MOVE_PMD is already enabled on x86 : N/A
- Enabling HAVE_MOVE_PUD on x86 : ~13x speed up

- Enabling HAVE_MOVE_PMD on arm64 : ~ 8x speed up
- Enabling HAVE_MOVE_PUD on arm64 : ~19x speed up

Altogether, HAVE_MOVE_PMD and HAVE_MOVE_PUD
give a total of ~150x speed up on arm64.

Changes in v2:
- Reduce mremap_test time by only validating a configurable
threshold of the remapped region, as per John.
- Use a random pattern for mremap validation. Provide pattern
seed in test output, as per John.
- Moved set_pud_at() to separate patch, per Kirill.
- Use switch() instead of ifs in move_pgt_entry(), per Kirill.
- Update commit message with description of Android
garbage collector use case for HAVE_MOVE_PUD, as per Joel.
- Fix build test error reported by kernel test robot in [1].

[1] https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org/thread/CKPGL4FH4NG7TGH2CVYX2UX76L25BTA3/

Kalesh Singh (6):
kselftests: vm: Add mremap tests
arm64: mremap speedup - Enable HAVE_MOVE_PMD
mm: Speedup mremap on 1GB or larger regions
arm64: Add set_pud_at() functions
arm64: mremap speedup - Enable HAVE_MOVE_PUD
x86: mremap speedup - Enable HAVE_MOVE_PUD

arch/Kconfig | 7 +
arch/arm64/Kconfig | 2 +
arch/arm64/include/asm/pgtable.h | 1 +
arch/x86/Kconfig | 1 +
mm/mremap.c | 220 +++++++++++++--
tools/testing/selftests/vm/.gitignore | 1 +
tools/testing/selftests/vm/Makefile | 1 +
tools/testing/selftests/vm/mremap_test.c | 333 +++++++++++++++++++++++
tools/testing/selftests/vm/run_vmtests | 11 +
9 files changed, 547 insertions(+), 30 deletions(-)
create mode 100644 tools/testing/selftests/vm/mremap_test.c


base-commit: 472e5b056f000a778abb41f1e443de58eb259783
--
2.28.0.806.g8561365e88-goog

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