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kernel_optimize_test/arch/riscv/Kconfig
Vincent Chen ad5d1122b8
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>
2020-06-10 19:47:16 -07:00

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# SPDX-License-Identifier: GPL-2.0-only
#
# For a description of the syntax of this configuration file,
# see Documentation/kbuild/kconfig-language.rst.
#
config 64BIT
bool
config 32BIT
bool
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
select ARCH_HAS_GCOV_PROFILE_ALL
select ARCH_HAS_GIGANTIC_PAGE
select ARCH_HAS_MMIOWB
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_SET_DIRECT_MAP
select ARCH_HAS_SET_MEMORY
select ARCH_HAS_STRICT_KERNEL_RWX if MMU
select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
select ARCH_WANT_FRAME_POINTERS
select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
select CLONE_BACKWARDS
select COMMON_CLK
select EDAC_SUPPORT
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
select GENERIC_PCI_IOMAP
select GENERIC_PTDUMP if MMU
select GENERIC_SCHED_CLOCK
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
select HAVE_ARCH_KGDB
select HAVE_ARCH_KGDB_QXFER_PKT
select HAVE_ARCH_MMAP_RND_BITS if MMU
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_TRACEHOOK
select HAVE_ASM_MODVERSIONS
select HAVE_COPY_THREAD_TLS
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
select HAVE_PERF_USER_STACK_DUMP
select HAVE_SYSCALL_TRACEPOINTS
select IRQ_DOMAIN
select MODULES_USE_ELF_RELA if MODULES
select MODULE_SECTIONS if MODULES
select OF
select OF_EARLY_FLATTREE
select OF_IRQ
select PCI_DOMAINS_GENERIC if PCI
select PCI_MSI if PCI
select RISCV_INTC
select RISCV_TIMER
select SPARSEMEM_STATIC if 32BIT
select SPARSE_IRQ
select SYSCTL_EXCEPTION_TRACE
select THREAD_INFO_IN_TASK
config ARCH_MMAP_RND_BITS_MIN
default 18 if 64BIT
default 8
# max bits determined by the following formula:
# VA_BITS - PAGE_SHIFT - 3
config ARCH_MMAP_RND_BITS_MAX
default 24 if 64BIT # SV39 based
default 17
# set if we run in machine mode, cleared if we run in supervisor mode
config RISCV_M_MODE
bool
default !MMU
# set if we are running in S-mode and can use SBI calls
config RISCV_SBI
bool
depends on !RISCV_M_MODE
default y
config MMU
bool "MMU-based Paged Memory Management Support"
default y
help
Select if you want MMU-based virtualised addressing space
support by paged memory management. If unsure, say 'Y'.
config ZONE_DMA32
bool
default y if 64BIT
config VA_BITS
int
default 32 if 32BIT
default 39 if 64BIT
config PA_BITS
int
default 34 if 32BIT
default 56 if 64BIT
config PAGE_OFFSET
hex
default 0xC0000000 if 32BIT && MAXPHYSMEM_2GB
default 0x80000000 if 64BIT && !MMU
default 0xffffffff80000000 if 64BIT && MAXPHYSMEM_2GB
default 0xffffffe000000000 if 64BIT && MAXPHYSMEM_128GB
config ARCH_FLATMEM_ENABLE
def_bool y
config ARCH_SPARSEMEM_ENABLE
def_bool y
depends on MMU
select SPARSEMEM_VMEMMAP_ENABLE
config ARCH_SELECT_MEMORY_MODEL
def_bool ARCH_SPARSEMEM_ENABLE
config ARCH_WANT_GENERAL_HUGETLB
def_bool y
config ARCH_SUPPORTS_DEBUG_PAGEALLOC
def_bool y
config SYS_SUPPORTS_HUGETLBFS
depends on MMU
def_bool y
config STACKTRACE_SUPPORT
def_bool y
config TRACE_IRQFLAGS_SUPPORT
def_bool y
config GENERIC_BUG
def_bool y
depends on BUG
select GENERIC_BUG_RELATIVE_POINTERS if 64BIT
config GENERIC_BUG_RELATIVE_POINTERS
bool
config GENERIC_CALIBRATE_DELAY
def_bool y
config GENERIC_CSUM
def_bool y
config GENERIC_HWEIGHT
def_bool y
config FIX_EARLYCON_MEM
def_bool MMU
config PGTABLE_LEVELS
int
default 3 if 64BIT
default 2
source "arch/riscv/Kconfig.socs"
menu "Platform type"
choice
prompt "Base ISA"
default ARCH_RV64I
help
This selects the base ISA that this kernel will target and must match
the target platform.
config ARCH_RV32I
bool "RV32I"
select 32BIT
select GENERIC_LIB_ASHLDI3
select GENERIC_LIB_ASHRDI3
select GENERIC_LIB_LSHRDI3
select GENERIC_LIB_UCMPDI2
select MMU
config ARCH_RV64I
bool "RV64I"
select 64BIT
select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && GCC_VERSION >= 50000
select HAVE_DYNAMIC_FTRACE if MMU
select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
select SWIOTLB if MMU
endchoice
# We must be able to map all physical memory into the kernel, but the compiler
# is still a bit more efficient when generating code if it's setup in a manner
# such that it can only map 2GiB of memory.
choice
prompt "Kernel Code Model"
default CMODEL_MEDLOW if 32BIT
default CMODEL_MEDANY if 64BIT
config CMODEL_MEDLOW
bool "medium low code model"
config CMODEL_MEDANY
bool "medium any code model"
endchoice
config MODULE_SECTIONS
bool
select HAVE_MOD_ARCH_SPECIFIC
choice
prompt "Maximum Physical Memory"
default MAXPHYSMEM_2GB if 32BIT
default MAXPHYSMEM_2GB if 64BIT && CMODEL_MEDLOW
default MAXPHYSMEM_128GB if 64BIT && CMODEL_MEDANY
config MAXPHYSMEM_2GB
bool "2GiB"
config MAXPHYSMEM_128GB
depends on 64BIT && CMODEL_MEDANY
bool "128GiB"
endchoice
config SMP
bool "Symmetric Multi-Processing"
help
This enables support for systems with more than one CPU. If
you say N here, the kernel will run on single and
multiprocessor machines, but will use only one CPU of a
multiprocessor machine. If you say Y here, the kernel will run
on many, but not all, single processor machines. On a single
processor machine, the kernel will run faster if you say N
here.
If you don't know what to do here, say N.
config NR_CPUS
int "Maximum number of CPUs (2-32)"
range 2 32
depends on SMP
default "8"
config HOTPLUG_CPU
bool "Support for hot-pluggable CPUs"
depends on SMP
select GENERIC_IRQ_MIGRATION
help
Say Y here to experiment with turning CPUs off and on. CPUs
can be controlled through /sys/devices/system/cpu.
Say N if you want to disable CPU hotplug.
choice
prompt "CPU Tuning"
default TUNE_GENERIC
config TUNE_GENERIC
bool "generic"
endchoice
config RISCV_ISA_C
bool "Emit compressed instructions when building Linux"
default y
help
Adds "C" to the ISA subsets that the toolchain is allowed to emit
when building Linux, which results in compressed instructions in the
Linux binary.
If you don't know what to do here, say Y.
menu "supported PMU type"
depends on PERF_EVENTS
config RISCV_BASE_PMU
bool "Base Performance Monitoring Unit"
def_bool y
help
A base PMU that serves as a reference implementation and has limited
feature of perf. It can run on any RISC-V machines so serves as the
fallback, but this option can also be disable to reduce kernel size.
endmenu
config FPU
bool "FPU support"
default y
help
Say N here if you want to disable all floating-point related procedure
in the kernel.
If you don't know what to do here, say Y.
endmenu
menu "Kernel features"
source "kernel/Kconfig.hz"
config SECCOMP
bool "Enable seccomp to safely compute untrusted bytecode"
help
This kernel feature is useful for number crunching applications
that may need to compute untrusted bytecode during their
execution. By using pipes or other transports made available to
the process as file descriptors supporting the read/write
syscalls, it's possible to isolate those applications in
their own address space using seccomp. Once seccomp is
enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
and the task is only allowed to execute a few safe syscalls
defined by each seccomp mode.
config RISCV_SBI_V01
bool "SBI v0.1 support"
default y
depends on RISCV_SBI
help
This config allows kernel to use SBI v0.1 APIs. This will be
deprecated in future once legacy M-mode software are no longer in use.
endmenu
menu "Boot options"
config CMDLINE
string "Built-in kernel command line"
help
For most platforms, the arguments for the kernel's command line
are provided at run-time, during boot. However, there are cases
where either no arguments are being provided or the provided
arguments are insufficient or even invalid.
When that occurs, it is possible to define a built-in command
line here and choose how the kernel should use it later on.
choice
prompt "Built-in command line usage" if CMDLINE != ""
default CMDLINE_FALLBACK
help
Choose how the kernel will handle the provided built-in command
line.
config CMDLINE_FALLBACK
bool "Use bootloader kernel arguments if available"
help
Use the built-in command line as fallback in case we get nothing
during boot. This is the default behaviour.
config CMDLINE_EXTEND
bool "Extend bootloader kernel arguments"
help
The command-line arguments provided during boot will be
appended to the built-in command line. This is useful in
cases where the provided arguments are insufficient and
you don't want to or cannot modify them.
config CMDLINE_FORCE
bool "Always use the default kernel command string"
help
Always use the built-in command line, even if we get one during
boot. This is useful in case you need to override the provided
command line on systems where you don't have or want control
over it.
endchoice
endmenu
config BUILTIN_DTB
def_bool n
depends on RISCV_M_MODE
depends on OF
menu "Power management options"
source "kernel/power/Kconfig"
endmenu
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