[PATCH v2 0/3] RISC-V: ifunced memcpy using new kernel hwprobe interface
Evan Green
evan@rivosinc.com
Tue Feb 21 19:15:34 GMT 2023
This series illustrates the use of a proposed Linux syscall that
enumerates architectural information about the RISC-V cores the system
is running on. In this series we expose a small wrapper function around
the syscall. An ifunc selector for memcpy queries it to see if unaligned
access is "fast" on this hardware. If it is, it selects a newly provided
implementation of memcpy that doesn't work hard at aligning the src and
destination buffers.
This is somewhat of a proof of concept for the syscall itself, but I do
find that in my goofy memcpy test [1], the unaligned memcpy performed at
least as well as the generic C version. This is however on Qemu on an M1
mac, so not a test of any real hardware (more a smoke test that the
implementation isn't silly).
v3 of the Linux series can be found at [2].
[1] https://pastebin.com/Nj8ixpkX
[2] https://lore.kernel.org/lkml/20230221190858.3159617-1-evan@rivosinc.com/T/#t
Changes in v2:
- hwprobe.h: Use __has_include and duplicate Linux content to make
compilation work when Linux headers are absent (Adhemerval)
- hwprobe.h: Put declaration under __USE_GNU (Adhemerval)
- Use INLINE_SYSCALL_CALL (Adhemerval)
- Update versions
- Update UNALIGNED_MASK to match kernel v3 series.
- Add vDSO interface
- Used _MASK instead of _FAST value itself.
Evan Green (3):
riscv: Add Linux hwprobe syscall support
riscv: Add hwprobe vdso call support
riscv: Add and use alignment-ignorant memcpy
sysdeps/riscv/memcopy.h | 28 +++++
sysdeps/riscv/memcpy.c | 65 +++++++++++
sysdeps/riscv/memcpy_noalignment.S | 103 ++++++++++++++++++
sysdeps/unix/sysv/linux/dl-vdso-setup.c | 10 ++
sysdeps/unix/sysv/linux/dl-vdso-setup.h | 3 +
sysdeps/unix/sysv/linux/riscv/Makefile | 8 +-
sysdeps/unix/sysv/linux/riscv/Versions | 3 +
sysdeps/unix/sysv/linux/riscv/hwprobe.c | 36 ++++++
.../unix/sysv/linux/riscv/memcpy-generic.c | 24 ++++
.../unix/sysv/linux/riscv/rv32/arch-syscall.h | 1 +
.../unix/sysv/linux/riscv/rv32/libc.abilist | 1 +
.../unix/sysv/linux/riscv/rv64/arch-syscall.h | 1 +
.../unix/sysv/linux/riscv/rv64/libc.abilist | 1 +
sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h | 67 ++++++++++++
sysdeps/unix/sysv/linux/riscv/sysdep.h | 1 +
sysdeps/unix/sysv/linux/syscall-names.list | 1 +
16 files changed, 351 insertions(+), 2 deletions(-)
create mode 100644 sysdeps/riscv/memcopy.h
create mode 100644 sysdeps/riscv/memcpy.c
create mode 100644 sysdeps/riscv/memcpy_noalignment.S
create mode 100644 sysdeps/unix/sysv/linux/riscv/hwprobe.c
create mode 100644 sysdeps/unix/sysv/linux/riscv/memcpy-generic.c
create mode 100644 sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
--
2.25.1
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