If in doubt, say "N".
config JUMP_LABEL
- bool "Optimize trace point call sites"
+ bool "Optimize very unlikely/likely branches"
depends on HAVE_ARCH_JUMP_LABEL
help
+ This option enables a transparent branch optimization that
+ makes certain almost-always-true or almost-always-false branch
+ conditions even cheaper to execute within the kernel.
+
+ Certain performance-sensitive kernel code, such as trace points,
+ scheduler functionality, networking code and KVM have such
+ branches and include support for this optimization technique.
+
If it is detected that the compiler has support for "asm goto",
- the kernel will compile trace point locations with just a
- nop instruction. When trace points are enabled, the nop will
- be converted to a jump to the trace function. This technique
- lowers overhead and stress on the branch prediction of the
- processor.
+ the kernel will compile such branches with just a nop
+ instruction. When the condition flag is toggled to true, the
+ nop will be converted to a jump instruction to execute the
+ conditional block of instructions.
- On i386, options added to the compiler flags may increase
- the size of the kernel slightly.
+ This technique lowers overhead and stress on the branch prediction
+ of the processor and generally makes the kernel faster. The update
+ of the condition is slower, but those are always very rare.
+
+ ( On 32-bit x86, the necessary options added to the compiler
+ flags may increase the size of the kernel slightly. )
config OPTPROBES
def_bool y
depends on KPROBES && HAVE_OPTPROBES
depends on !PREEMPT
+config UPROBES
+ bool "Transparent user-space probes (EXPERIMENTAL)"
+ depends on ARCH_SUPPORTS_UPROBES && PERF_EVENTS
+ default n
+ help
+ Uprobes is the user-space counterpart to kprobes: they
+ enable instrumentation applications (such as 'perf probe')
+ to establish unintrusive probes in user-space binaries and
+ libraries, by executing handler functions when the probes
+ are hit by user-space applications.
+
+ ( These probes come in the form of single-byte breakpoints,
+ managed by the kernel and kept transparent to the probed
+ application. )
+
+ If in doubt, say "N".
+
config HAVE_EFFICIENT_UNALIGNED_ACCESS
bool
help
config HAVE_OPTPROBES
bool
+
+config HAVE_NMI_WATCHDOG
+ bool
#
# An arch should select this if it provides all these things:
#
config HAVE_CMPXCHG_DOUBLE
bool
+config ARCH_WANT_OLD_COMPAT_IPC
+ bool
+
source "kernel/gcov/Kconfig"