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Cruslan
n00b
Joined: 06 Jan 2024
Posts: 26
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 Posted: Sun Jun 30, 2024 7:33 pm Post subject: [Solved] How to set CFLAGS to kernels compiled by genkernel? |
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I want to compile kernel with CFLAGS added by genkernel. But i can't find any information in Gentoo documentation. I found a topic that the guy succeed by adding "KERNEL_CFLAGS" variable to /etc/genkernel.conf; https://forums.gentoo.org/viewtopic-p-8785123.html?sid=ffc4f016ae4af7f94b4288619e030a1b It will work or is there any method to kernel built by requested CFLAGS by genkernel? Is it correct usage for CFLAGS in kernel building;
/etc/genkernel.conf
| Code: | | KERNEL_CFLAGS="-march=native -mtune=native -O3 -pipe -flto=12 -fuse-linker-plugin -ftree-loop-optimize -fgraphite-identity -floop-nest-optimize -floop-parallelize-all -fdevirtualize-at-ltrans -fipa-pta -fno-semantic-interposition" |
Last edited by Cruslan on Mon Jul 01, 2024 4:30 pm; edited 1 time in total |
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Cruslan
n00b
Joined: 06 Jan 2024
Posts: 26
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| Posted: Mon Jul 01, 2024 4:29 pm Post subject: |
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I succeed my goal by cherry-picking TKG-Kernel's "0013-optimize_harder_O3.patch" file in https://github.com/Frogging-Family/linux-tkg/blob/master/linux-tkg-patches/6.9/0013-optimize_harder_O3.patch. I changed default options to my desired CFLAGS. After that i applied patch by emerge to sys-kernel/gentoo-kernel. Lastly i compiled kernel as usual.
Original patch;
| Code: | diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -442,7 +442,7 @@ endif
HOSTPKG_CONFIG = pkg-config
KBUILD_USERHOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
- -O2 -fomit-frame-pointer -std=gnu11
+ -O3 -fomit-frame-pointer -std=gnu11
KBUILD_USERCFLAGS := $(KBUILD_USERHOSTCFLAGS) $(USERCFLAGS)
KBUILD_USERLDFLAGS := $(USERLDFLAGS)
@@ -474,7 +474,7 @@ endif
-Wclippy::dbg_macro
KBUILD_HOSTCFLAGS := $(KBUILD_USERHOSTCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
-KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
+KBUILD_HOSTCXXFLAGS := -Wall -O3 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
KBUILD_HOSTRUSTFLAGS := $(rust_common_flags) -O -Cstrip=debuginfo \
-Zallow-features= $(HOSTRUSTFLAGS)
KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
@@ -757,7 +757,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
-KBUILD_CFLAGS += -O2
+KBUILD_CFLAGS += -O3
KBUILD_RUSTFLAGS += -Copt-level=2
else ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
KBUILD_CFLAGS += -Os
diff --git a/init/Kconfig b/init/Kconfig
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1401,10 +1401,10 @@ choice
default CC_OPTIMIZE_FOR_PERFORMANCE
config CC_OPTIMIZE_FOR_PERFORMANCE
- bool "Optimize for performance (-O2)"
+ bool "Optimize for performance (-O3)"
help
This is the default optimization level for the kernel, building
- with the "-O2" compiler flag for best performance and most
+ with the "-O3" compiler flag for best performance and most
helpful compile-time warnings.
config CC_OPTIMIZE_FOR_SIZE |
Edited patch;
| Code: | diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -442,7 +442,7 @@ endif
HOSTPKG_CONFIG = pkg-config
KBUILD_USERHOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
- -O2 -fomit-frame-pointer -std=gnu11
+ -O3 -fomit-frame-pointer -std=gnu11 -flto=12 -fuse-linker-plugin -ftree-loop-optimize -fgraphite-identity -floop-nest-optimize -floop-parallelize-all -fdevirtualize-at-ltrans -fipa-pta -fno-semantic-interposition
KBUILD_USERCFLAGS := $(KBUILD_USERHOSTCFLAGS) $(USERCFLAGS)
KBUILD_USERLDFLAGS := $(USERLDFLAGS)
@@ -474,7 +474,7 @@ endif
-Wclippy::dbg_macro
KBUILD_HOSTCFLAGS := $(KBUILD_USERHOSTCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
-KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
+KBUILD_HOSTCXXFLAGS := -Wall -O3 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
KBUILD_HOSTRUSTFLAGS := $(rust_common_flags) -O -Cstrip=debuginfo \
-Zallow-features= $(HOSTRUSTFLAGS)
KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
@@ -757,7 +757,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
-KBUILD_CFLAGS += -O2
+KBUILD_CFLAGS += -O3
KBUILD_RUSTFLAGS += -Copt-level=2
else ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
KBUILD_CFLAGS += -Os
diff --git a/init/Kconfig b/init/Kconfig
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1401,10 +1401,10 @@ choice
default CC_OPTIMIZE_FOR_PERFORMANCE
config CC_OPTIMIZE_FOR_PERFORMANCE
- bool "Optimize for performance (-O2)"
+ bool "Optimize for performance (-O3)"
help
This is the default optimization level for the kernel, building
- with the "-O2" compiler flag for best performance and most
+ with the "-O3" compiler flag for best performance and most
helpful compile-time warnings.
config CC_OPTIMIZE_FOR_SIZE |
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