diff options
| author | Vincent Chen <vincent.chen@sifive.com> | 2020-06-09 22:14:48 +0800 |
|---|---|---|
| committer | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-06-10 19:47:16 -0700 |
| commit | ad5d1122b82fbd6a816d1b9d26ee01a6dbc2d757 (patch) | |
| tree | 5e78643855b7be7a1bcffc4c7ee2769323ab181f /arch/riscv/Kconfig | |
| parent | 05589dde649cd954a122b0ebb2cbe4ade8a80e98 (diff) | |
riscv: use vDSO common flow to reduce the latency of the time-related functions
Even if RISC-V has supported the vDSO feature, the latency of the functions
for obtaining the system time is still expensive. It is because these
functions still trigger a corresponding system call in the process, which
slows down the response time. If we want to remove the system call to
reduce the latency, the kernel should have the ability to output the system
clock information to userspace. This patch introduces the vDSO common flow
to enable the kernel to achieve the above feature and uses "rdtime"
instruction to obtain the current time in the user space. Under this
condition, the latency cost by the ecall from U-mode to S-mode can be
eliminated. After applying this patch, the latency of gettimeofday()
measured on the HiFive unleashed board can be reduced by %61.
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Diffstat (limited to 'arch/riscv/Kconfig')
| -rw-r--r-- | arch/riscv/Kconfig | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 7c9614909d2c..128192e14ff2 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -12,6 +12,7 @@ config 32BIT config RISCV def_bool y + select ARCH_CLOCKSOURCE_INIT select ARCH_HAS_BINFMT_FLAT select ARCH_HAS_DEBUG_VIRTUAL if MMU select ARCH_HAS_DEBUG_WX @@ -31,6 +32,7 @@ config RISCV select GENERIC_ARCH_TOPOLOGY if SMP select GENERIC_ATOMIC64 if !64BIT select GENERIC_CLOCKEVENTS + select GENERIC_GETTIMEOFDAY if HAVE_GENERIC_VDSO select GENERIC_IOREMAP select GENERIC_IRQ_MULTI_HANDLER select GENERIC_IRQ_SHOW @@ -40,6 +42,7 @@ config RISCV select GENERIC_SMP_IDLE_THREAD select GENERIC_STRNCPY_FROM_USER if MMU select GENERIC_STRNLEN_USER if MMU + select GENERIC_TIME_VSYSCALL if MMU && 64BIT select HANDLE_DOMAIN_IRQ select HAVE_ARCH_AUDITSYSCALL select HAVE_ARCH_KASAN if MMU && 64BIT @@ -53,6 +56,7 @@ config RISCV select HAVE_DMA_CONTIGUOUS if MMU select HAVE_EBPF_JIT if MMU select HAVE_FUTEX_CMPXCHG if FUTEX + select HAVE_GENERIC_VDSO if MMU && 64BIT select HAVE_PCI select HAVE_PERF_EVENTS select HAVE_PERF_REGS |