| Message ID | 20240130-use_mmap_hint_address-v2-0-f34ebfd33053@rivosinc.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | riscv: mm: Use hint address in mmap if available | expand |
Hello: This series was applied to riscv/linux.git (for-next) by Palmer Dabbelt <palmer@rivosinc.com>: On Tue, 30 Jan 2024 11:04:29 -0800 you wrote: > On riscv, mmap currently returns an address from the largest address > space that can fit entirely inside of the hint address. This makes it > such that the hint address is almost never returned. This patch raises > the mappable area up to and including the hint address. This allows mmap > to often return the hint address, which allows a performance improvement > over searching for a valid address as well as making the behavior more > similar to other architectures. > > [...] Here is the summary with links: - [v2,1/3] riscv: mm: Use hint address in mmap if available (no matching commit) - [v2,2/3] selftests: riscv: Generalize mm selftests (no matching commit) - [v2,3/3] docs: riscv: Define behavior of mmap https://git.kernel.org/riscv/c/371a3c2055db You are awesome, thank you!
On riscv, mmap currently returns an address from the largest address space that can fit entirely inside of the hint address. This makes it such that the hint address is almost never returned. This patch raises the mappable area up to and including the hint address. This allows mmap to often return the hint address, which allows a performance improvement over searching for a valid address as well as making the behavior more similar to other architectures. Note that a previous patch introduced stronger semantics compared to other architectures for riscv mmap. On riscv, mmap will not use bits in the upper bits of the virtual address depending on the hint address. On other architectures, a random address is returned in the address space requested. On all architectures the hint address will be returned if it is available. This allows riscv applications to configure how many bits in the virtual address should be left empty. This has the two benefits of being able to request address spaces that are smaller than the default and doesn't require the application to know the page table layout of riscv. Signed-off-by: Charlie Jenkins <charlie@rivosinc.com> --- Changes in v2: - Add back forgotten "mmap_end = STACK_TOP_MAX" - Link to v1: https://lore.kernel.org/r/20240129-use_mmap_hint_address-v1-0-4c74da813ba1@rivosinc.com --- Charlie Jenkins (3): riscv: mm: Use hint address in mmap if available selftests: riscv: Generalize mm selftests docs: riscv: Define behavior of mmap Documentation/arch/riscv/vm-layout.rst | 16 ++-- arch/riscv/include/asm/processor.h | 22 +++--- tools/testing/selftests/riscv/mm/mmap_bottomup.c | 20 +---- tools/testing/selftests/riscv/mm/mmap_default.c | 20 +---- tools/testing/selftests/riscv/mm/mmap_test.h | 93 +++++++++++++----------- 5 files changed, 67 insertions(+), 104 deletions(-) --- base-commit: 556e2d17cae620d549c5474b1ece053430cd50bc change-id: 20240119-use_mmap_hint_address-f9f4b1b6f5f1