{chiron,sagit}_defconfig: enable JUMP_LABEL

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 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.

This technique lowers overhead and stress on the branchprediction
of the processor and generally makes the kernel faster.
The update of the condition is slower, but those are always
very rare.

Change-Id: I90657cf7ef3b9d116eb019da87dd62e1806e0e87
Signed-off-by: joshuous <joshuous@gmail.com>

diff --git a/arch/arm64/configs/chiron_defconfig b/arch/arm64/configs/chiron_defconfig
index 32d2f20..6390358 100644 (file)
--- a/arch/arm64/configs/chiron_defconfig
+++ b/arch/arm64/configs/chiron_defconfig
@@ -40,6 +40,7 @@ CONFIG_EMBEDDED=y
 # CONFIG_SLUB_DEBUG is not set
 # CONFIG_COMPAT_BRK is not set
 CONFIG_PROFILING=y
+CONFIG_JUMP_LABEL=y
 CONFIG_CC_STACKPROTECTOR_STRONG=y
 CONFIG_ARCH_MMAP_RND_COMPAT_BITS=16
 CONFIG_MODULES=y

diff --git a/arch/arm64/configs/sagit_defconfig b/arch/arm64/configs/sagit_defconfig
index 95989cd..bebfc12 100644 (file)
--- a/arch/arm64/configs/sagit_defconfig
+++ b/arch/arm64/configs/sagit_defconfig
@@ -40,6 +40,7 @@ CONFIG_EMBEDDED=y
 # CONFIG_SLUB_DEBUG is not set
 # CONFIG_COMPAT_BRK is not set
 CONFIG_PROFILING=y
+CONFIG_JUMP_LABEL=y
 CONFIG_CC_STACKPROTECTOR_STRONG=y
 CONFIG_ARCH_MMAP_RND_COMPAT_BITS=16
 CONFIG_MODULES=y