Add the build support for using Clang's Propeller optimizer. Like
AutoFDO, Propeller uses hardware sampling to gather information
about the frequency of execution of different code paths within a
binary. This information is then used to guide the compiler's
optimization decisions, resulting in a more efficient binary.
The support requires a Clang compiler LLVM 19 or later, and the
create_llvm_prof tool
(https://github.com/google/autofdo/releases/tag/v0.30.1). This
commit is limited to x86 platforms that support PMU features
like LBR on Intel machines and AMD Zen3 BRS.
Here is an example workflow for building an AutoFDO+Propeller
optimized kernel:
1) Build the kernel on the host machine, with AutoFDO and Propeller
build config
CONFIG_AUTOFDO_CLANG=y
CONFIG_PROPELLER_CLANG=y
then
$ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile>
“<autofdo_profile>” is the profile collected when doing a non-Propeller
AutoFDO build. This step builds a kernel that has the same optimization
level as AutoFDO, plus a metadata section that records basic block
information. This kernel image runs as fast as an AutoFDO optimized
kernel.
2) Install the kernel on test/production machines.
3) Run the load tests. The '-c' option in perf specifies the sample
event period. We suggest using a suitable prime number,
like 500009, for this purpose.
For Intel platforms:
$ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c <count> \
-o <perf_file> -- <loadtest>
For AMD platforms:
The supported system are: Zen3 with BRS, or Zen4 with amd_lbr_v2
# To see if Zen3 support LBR:
$ cat proc/cpuinfo | grep " brs"
# To see if Zen4 support LBR:
$ cat proc/cpuinfo | grep amd_lbr_v2
# If the result is yes, then collect the profile using:
$ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a \
-N -b -c <count> -o <perf_file> -- <loadtest>
4) (Optional) Download the raw perf file to the host machine.
5) Generate Propeller profile:
$ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> \
--format=propeller --propeller_output_module_name \
--out=<propeller_profile_prefix>_cc_profile.txt \
--propeller_symorder=<propeller_profile_prefix>_ld_profile.txt
“create_llvm_prof” is the profile conversion tool, and a prebuilt
binary for linux can be found on
https://github.com/google/autofdo/releases/tag/v0.30.1 (can also build
from source).
"<propeller_profile_prefix>" can be something like
"/home/user/dir/any_string".
This command generates a pair of Propeller profiles:
"<propeller_profile_prefix>_cc_profile.txt" and
"<propeller_profile_prefix>_ld_profile.txt".
6) Rebuild the kernel using the AutoFDO and Propeller profile files.
CONFIG_AUTOFDO_CLANG=y
CONFIG_PROPELLER_CLANG=y
and
$ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile> \
CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix>
Co-developed-by: Han Shen <shenhan@google.com>
Signed-off-by: Han Shen <shenhan@google.com>
Signed-off-by: Rong Xu <xur@google.com>
Suggested-by: Sriraman Tallam <tmsriram@google.com>
Suggested-by: Krzysztof Pszeniczny <kpszeniczny@google.com>
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Suggested-by: Stephane Eranian <eranian@google.com>
Tested-by: Yonghong Song <yonghong.song@linux.dev>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <kees@kernel.org>
---
Documentation/dev-tools/index.rst | 1 +
Documentation/dev-tools/propeller.rst | 162 ++++++++++++++++++++++++++
MAINTAINERS | 7 ++
Makefile | 1 +
arch/Kconfig | 19 +++
arch/x86/Kconfig | 1 +
arch/x86/kernel/vmlinux.lds.S | 4 +
include/asm-generic/vmlinux.lds.h | 6 +-
scripts/Makefile.lib | 10 ++
scripts/Makefile.propeller | 28 +++++
tools/objtool/check.c | 1 +
11 files changed, 237 insertions(+), 3 deletions(-)
create mode 100644 Documentation/dev-tools/propeller.rst
create mode 100644 scripts/Makefile.propeller
diff --git a/Documentation/dev-tools/index.rst b/Documentation/dev-tools/index.rst
index 6945644f7008a..3c0ac08b27091 100644
--- a/Documentation/dev-tools/index.rst
+++ b/Documentation/dev-tools/index.rst
@@ -35,6 +35,7 @@ Documentation/dev-tools/testing-overview.rst
checkuapi
gpio-sloppy-logic-analyzer
autofdo
+ propeller
.. only:: subproject and html
diff --git a/Documentation/dev-tools/propeller.rst b/Documentation/dev-tools/propeller.rst
new file mode 100644
index 0000000000000..92195958e3dbc
--- /dev/null
+++ b/Documentation/dev-tools/propeller.rst
@@ -0,0 +1,162 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================================
+Using Propeller with the Linux kernel
+=====================================
+
+This enables Propeller build support for the kernel when using Clang
+compiler. Propeller is a profile-guided optimization (PGO) method used
+to optimize binary executables. Like AutoFDO, it utilizes hardware
+sampling to gather information about the frequency of execution of
+different code paths within a binary. Unlike AutoFDO, this information
+is then used right before linking phase to optimize (among others)
+block layout within and across functions.
+
+A few important notes about adopting Propeller optimization:
+
+#. Although it can be used as a standalone optimization step, it is
+ strongly recommended to apply Propeller on top of AutoFDO,
+ AutoFDO+ThinLTO or Instrument FDO. The rest of this document
+ assumes this paradigm.
+
+#. Propeller uses another round of profiling on top of
+ AutoFDO/AutoFDO+ThinLTO/iFDO. The whole build process involves
+ "build-afdo - train-afdo - build-propeller - train-propeller -
+ build-optimized".
+
+#. Propeller requires LLVM 19 release or later for Clang/Clang++
+ and the linker(ld.lld).
+
+#. In addition to LLVM toolchain, Propeller requires a profiling
+ conversion tool: https://github.com/google/autofdo with a release
+ after v0.30.1: https://github.com/google/autofdo/releases/tag/v0.30.1.
+
+The Propeller optimization process involves the following steps:
+
+#. Initial building: Build the AutoFDO or AutoFDO+ThinLTO binary as
+ you would normally do, but with a set of compile-time / link-time
+ flags, so that a special metadata section is created within the
+ kernel binary. The special section is only intend to be used by the
+ profiling tool, it is not part of the runtime image, nor does it
+ change kernel run time text sections.
+
+#. Profiling: The above kernel is then run with a representative
+ workload to gather execution frequency data. This data is collected
+ using hardware sampling, via perf. Propeller is most effective on
+ platforms supporting advanced PMU features like LBR on Intel
+ machines. This step is the same as profiling the kernel for AutoFDO
+ (the exact perf parameters can be different).
+
+#. Propeller profile generation: Perf output file is converted to a
+ pair of Propeller profiles via an offline tool.
+
+#. Optimized build: Build the AutoFDO or AutoFDO+ThinLTO optimized
+ binary as you would normally do, but with a compile-time /
+ link-time flag to pick up the Propeller compile time and link time
+ profiles. This build step uses 3 profiles - the AutoFDO profile,
+ the Propeller compile-time profile and the Propeller link-time
+ profile.
+
+#. Deployment: The optimized kernel binary is deployed and used
+ in production environments, providing improved performance
+ and reduced latency.
+
+Preparation
+===========
+
+Configure the kernel with::
+
+ CONFIG_AUTOFDO_CLANG=y
+ CONFIG_PROPELLER_CLANG=y
+
+Customization
+=============
+
+The default CONFIG_PROPELLER_CLANG setting covers kernel space objects
+for Propeller builds. One can, however, enable or disable Propeller build
+for individual files and directories by adding a line similar to the
+following to the respective kernel Makefile:
+
+- For enabling a single file (e.g. foo.o)::
+
+ PROPELLER_PROFILE_foo.o := y
+
+- For enabling all files in one directory::
+
+ PROPELLER_PROFILE := y
+
+- For disabling one file::
+
+ PROPELLER_PROFILE_foo.o := n
+
+- For disabling all files in one directory::
+
+ PROPELLER__PROFILE := n
+
+
+Workflow
+========
+
+Here is an example workflow for building an AutoFDO+Propeller kernel:
+
+1) Assuming an AutoFDO profile is already collected following
+ instructions in the AutoFDO document, build the kernel on the host
+ machine, with AutoFDO and Propeller build configs ::
+
+ CONFIG_AUTOFDO_CLANG=y
+ CONFIG_PROPELLER_CLANG=y
+
+ and ::
+
+ $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo-profile-name>
+
+2) Install the kernel on the test machine.
+
+3) Run the load tests. The '-c' option in perf specifies the sample
+ event period. We suggest using a suitable prime number, like 500009,
+ for this purpose.
+
+ - For Intel platforms::
+
+ $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c <count> -o <perf_file> -- <loadtest>
+
+ - For AMD platforms::
+
+ $ perf record --pfm-event RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c <count> -o <perf_file> -- <loadtest>
+
+ Note you can repeat the above steps to collect multiple <perf_file>s.
+
+4) (Optional) Download the raw perf file(s) to the host machine.
+
+5) Use the create_llvm_prof tool (https://github.com/google/autofdo) to
+ generate Propeller profile. ::
+
+ $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file>
+ --format=propeller --propeller_output_module_name
+ --out=<propeller_profile_prefix>_cc_profile.txt
+ --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt
+
+ "<propeller_profile_prefix>" can be something like "/home/user/dir/any_string".
+
+ This command generates a pair of Propeller profiles:
+ "<propeller_profile_prefix>_cc_profile.txt" and
+ "<propeller_profile_prefix>_ld_profile.txt".
+
+ If there are more than 1 perf_file collected in the previous step,
+ you can create a temp list file "<perf_file_list>" with each line
+ containing one perf file name and run::
+
+ $ create_llvm_prof --binary=<vmlinux> --profile=@<perf_file_list>
+ --format=propeller --propeller_output_module_name
+ --out=<propeller_profile_prefix>_cc_profile.txt
+ --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt
+
+6) Rebuild the kernel using the AutoFDO and Propeller
+ profiles. ::
+
+ CONFIG_AUTOFDO_CLANG=y
+ CONFIG_PROPELLER_CLANG=y
+
+ and ::
+
+ $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<profile_file> CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix>
diff --git a/MAINTAINERS b/MAINTAINERS
index d6ea49433747a..42e3af0791e15 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18449,6 +18449,13 @@ S: Maintained
F: include/linux/psi*
F: kernel/sched/psi.c
+PROPELLER BUILD
+M: Rong Xu <xur@google.com>
+M: Han Shen <shenhan@google.com>
+S: Supported
+F: Documentation/dev-tools/propeller.rst
+F: scripts/Makefile.propeller
+
PRINTK
M: Petr Mladek <pmladek@suse.com>
R: Steven Rostedt <rostedt@goodmis.org>
diff --git a/Makefile b/Makefile
index b89d87b5dca79..b2830b27e1a7f 100644
--- a/Makefile
+++ b/Makefile
@@ -1019,6 +1019,7 @@ include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan
include-$(CONFIG_KCOV) += scripts/Makefile.kcov
include-$(CONFIG_RANDSTRUCT) += scripts/Makefile.randstruct
include-$(CONFIG_AUTOFDO_CLANG) += scripts/Makefile.autofdo
+include-$(CONFIG_PROPELLER_CLANG) += scripts/Makefile.propeller
include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins
include $(addprefix $(srctree)/, $(include-y))
diff --git a/arch/Kconfig b/arch/Kconfig
index 8dca3b5e6ef53..00551f340dbe3 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -831,6 +831,25 @@ config AUTOFDO_CLANG
If unsure, say N.
+config ARCH_SUPPORTS_PROPELLER_CLANG
+ bool
+
+config PROPELLER_CLANG
+ bool "Enable Clang's Propeller build"
+ depends on ARCH_SUPPORTS_PROPELLER_CLANG
+ depends on CC_IS_CLANG && CLANG_VERSION >= 190000
+ help
+ This option enables Clang’s Propeller build. When the Propeller
+ profiles is specified in variable CLANG_PROPELLER_PROFILE_PREFIX
+ during the build process, Clang uses the profiles to optimize
+ the kernel.
+
+ If no profile is specified, Propeller options are still passed
+ to Clang to facilitate the collection of perf data for creating
+ the Propeller profiles in subsequent builds.
+
+ If unsure, say N.
+
config ARCH_SUPPORTS_CFI_CLANG
bool
help
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9dc87661fb373..89b8fc452a7cf 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -127,6 +127,7 @@ config X86
select ARCH_SUPPORTS_LTO_CLANG_THIN
select ARCH_SUPPORTS_RT
select ARCH_SUPPORTS_AUTOFDO_CLANG
+ select ARCH_SUPPORTS_PROPELLER_CLANG if X86_64
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64
select ARCH_USE_MEMTEST
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index b8c5741d2fb48..cf22081601ed6 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -443,6 +443,10 @@ SECTIONS
STABS_DEBUG
DWARF_DEBUG
+#ifdef CONFIG_PROPELLER_CLANG
+ .llvm_bb_addr_map : { *(.llvm_bb_addr_map) }
+#endif
+
ELF_DETAILS
DISCARDS
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 8a0bb3946cf05..c995474e4c649 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -95,14 +95,14 @@
* With LTO_CLANG, the linker also splits sections by default, so we need
* these macros to combine the sections during the final link.
*
- * With AUTOFDO_CLANG, by default, the linker splits text sections and
- * regroups functions into subsections.
+ * With AUTOFDO_CLANG and PROPELLER_CLANG, by default, the linker splits
+ * text sections and regroups functions into subsections.
*
* RODATA_MAIN is not used because existing code already defines .rodata.x
* sections to be brought in with rodata.
*/
#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \
-defined(CONFIG_AUTOFDO_CLANG)
+defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
#define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
#else
#define TEXT_MAIN .text
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 2d0942c1a0277..e7859ad90224a 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -201,6 +201,16 @@ _c_flags += $(if $(patsubst n%,, \
$(CFLAGS_AUTOFDO_CLANG))
endif
+#
+# Enable Propeller build flags except some files or directories we don't want to
+# enable (depends on variables AUTOFDO_PROPELLER_obj.o and PROPELLER_PROFILE).
+#
+ifdef CONFIG_PROPELLER_CLANG
+_c_flags += $(if $(patsubst n%,, \
+ $(AUTOFDO_PROFILE_$(target-stem).o)$(AUTOFDO_PROFILE)$(PROPELLER_PROFILE))$(is-kernel-object), \
+ $(CFLAGS_PROPELLER_CLANG))
+endif
+
# $(src) for including checkin headers from generated source files
# $(obj) for including generated headers from checkin source files
ifeq ($(KBUILD_EXTMOD),)
diff --git a/scripts/Makefile.propeller b/scripts/Makefile.propeller
new file mode 100644
index 0000000000000..344190717e471
--- /dev/null
+++ b/scripts/Makefile.propeller
@@ -0,0 +1,28 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# Enable available and selected Clang Propeller features.
+ifdef CLANG_PROPELLER_PROFILE_PREFIX
+ CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=list=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt -ffunction-sections
+ KBUILD_LDFLAGS += --symbol-ordering-file=$(CLANG_PROPELLER_PROFILE_PREFIX)_ld_profile.txt --no-warn-symbol-ordering
+else
+ CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=labels
+endif
+
+# Propeller requires debug information to embed module names in the profiles.
+# If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. Skip this for AutoFDO,
+# as the option should already be set.
+ifndef CONFIG_DEBUG_INFO
+ ifndef CONFIG_AUTOFDO_CLANG
+ CFLAGS_PROPELLER_CLANG += -gmlt
+ endif
+endif
+
+ifdef CONFIG_LTO_CLANG_THIN
+ ifdef CLANG_PROPELLER_PROFILE_PREFIX
+ KBUILD_LDFLAGS += --lto-basic-block-sections=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt
+ else
+ KBUILD_LDFLAGS += --lto-basic-block-sections=labels
+ endif
+endif
+
+export CFLAGS_PROPELLER_CLANG
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4c5229991e1e0..05a0fb4a3d1a0 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4558,6 +4558,7 @@ static int validate_ibt(struct objtool_file *file)
!strcmp(sec->name, "__mcount_loc") ||
!strcmp(sec->name, ".kcfi_traps") ||
!strcmp(sec->name, ".llvm.call-graph-profile") ||
+ !strcmp(sec->name, ".llvm_bb_addr_map") ||
strstr(sec->name, "__patchable_function_entries"))
continue;
--
2.47.0.163.g1226f6d8fa-goog
On 11/2/24 10:51 AM, Rong Xu wrote:
> Add the build support for using Clang's Propeller optimizer. Like
> AutoFDO, Propeller uses hardware sampling to gather information
> about the frequency of execution of different code paths within a
> binary. This information is then used to guide the compiler's
> optimization decisions, resulting in a more efficient binary.
>
> The support requires a Clang compiler LLVM 19 or later, and the
> create_llvm_prof tool
> (https://github.com/google/autofdo/releases/tag/v0.30.1). This
> commit is limited to x86 platforms that support PMU features
> like LBR on Intel machines and AMD Zen3 BRS.
>
> Here is an example workflow for building an AutoFDO+Propeller
> optimized kernel:
>
> 1) Build the kernel on the host machine, with AutoFDO and Propeller
> build config
> CONFIG_AUTOFDO_CLANG=y
> CONFIG_PROPELLER_CLANG=y
> then
> $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile>
>
> “<autofdo_profile>” is the profile collected when doing a non-Propeller
> AutoFDO build. This step builds a kernel that has the same optimization
> level as AutoFDO, plus a metadata section that records basic block
> information. This kernel image runs as fast as an AutoFDO optimized
> kernel.
>
> 2) Install the kernel on test/production machines.
>
> 3) Run the load tests. The '-c' option in perf specifies the sample
> event period. We suggest using a suitable prime number,
> like 500009, for this purpose.
> For Intel platforms:
> $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c <count> \
> -o <perf_file> -- <loadtest>
> For AMD platforms:
> The supported system are: Zen3 with BRS, or Zen4 with amd_lbr_v2
> # To see if Zen3 support LBR:
> $ cat proc/cpuinfo | grep " brs"
> # To see if Zen4 support LBR:
> $ cat proc/cpuinfo | grep amd_lbr_v2
> # If the result is yes, then collect the profile using:
> $ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a \
> -N -b -c <count> -o <perf_file> -- <loadtest>
>
> 4) (Optional) Download the raw perf file to the host machine.
>
> 5) Generate Propeller profile:
> $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> \
> --format=propeller --propeller_output_module_name \
> --out=<propeller_profile_prefix>_cc_profile.txt \
> --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt
>
> “create_llvm_prof” is the profile conversion tool, and a prebuilt
> binary for linux can be found on
> https://github.com/google/autofdo/releases/tag/v0.30.1 (can also build
> from source).
>
> "<propeller_profile_prefix>" can be something like
> "/home/user/dir/any_string".
>
> This command generates a pair of Propeller profiles:
> "<propeller_profile_prefix>_cc_profile.txt" and
> "<propeller_profile_prefix>_ld_profile.txt".
>
> 6) Rebuild the kernel using the AutoFDO and Propeller profile files.
> CONFIG_AUTOFDO_CLANG=y
> CONFIG_PROPELLER_CLANG=y
> and
> $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile> \
> CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix>
>
> Co-developed-by: Han Shen <shenhan@google.com>
> Signed-off-by: Han Shen <shenhan@google.com>
> Signed-off-by: Rong Xu <xur@google.com>
> Suggested-by: Sriraman Tallam <tmsriram@google.com>
> Suggested-by: Krzysztof Pszeniczny <kpszeniczny@google.com>
> Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> Suggested-by: Stephane Eranian <eranian@google.com>
> Tested-by: Yonghong Song <yonghong.song@linux.dev>
> Tested-by: Nathan Chancellor <nathan@kernel.org>
> Reviewed-by: Kees Cook <kees@kernel.org>
> ---
> Documentation/dev-tools/index.rst | 1 +
> Documentation/dev-tools/propeller.rst | 162 ++++++++++++++++++++++++++
> MAINTAINERS | 7 ++
> Makefile | 1 +
> arch/Kconfig | 19 +++
> arch/x86/Kconfig | 1 +
> arch/x86/kernel/vmlinux.lds.S | 4 +
> include/asm-generic/vmlinux.lds.h | 6 +-
> scripts/Makefile.lib | 10 ++
> scripts/Makefile.propeller | 28 +++++
> tools/objtool/check.c | 1 +
> 11 files changed, 237 insertions(+), 3 deletions(-)
> create mode 100644 Documentation/dev-tools/propeller.rst
> create mode 100644 scripts/Makefile.propeller
>
> diff --git a/Documentation/dev-tools/index.rst b/Documentation/dev-tools/index.rst
> index 6945644f7008a..3c0ac08b27091 100644
> --- a/Documentation/dev-tools/index.rst
> +++ b/Documentation/dev-tools/index.rst
> @@ -35,6 +35,7 @@ Documentation/dev-tools/testing-overview.rst
> checkuapi
> gpio-sloppy-logic-analyzer
> autofdo
> + propeller
>
>
> .. only:: subproject and html
> diff --git a/Documentation/dev-tools/propeller.rst b/Documentation/dev-tools/propeller.rst
> new file mode 100644
> index 0000000000000..92195958e3dbc
> --- /dev/null
> +++ b/Documentation/dev-tools/propeller.rst
> @@ -0,0 +1,162 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=====================================
> +Using Propeller with the Linux kernel
> +=====================================
> +
> +This enables Propeller build support for the kernel when using Clang
> +compiler. Propeller is a profile-guided optimization (PGO) method used
> +to optimize binary executables. Like AutoFDO, it utilizes hardware
> +sampling to gather information about the frequency of execution of
> +different code paths within a binary. Unlike AutoFDO, this information
> +is then used right before linking phase to optimize (among others)
> +block layout within and across functions.
> +
> +A few important notes about adopting Propeller optimization:
> +
> +#. Although it can be used as a standalone optimization step, it is
> + strongly recommended to apply Propeller on top of AutoFDO,
> + AutoFDO+ThinLTO or Instrument FDO. The rest of this document
> + assumes this paradigm.
> +
> +#. Propeller uses another round of profiling on top of
> + AutoFDO/AutoFDO+ThinLTO/iFDO. The whole build process involves
> + "build-afdo - train-afdo - build-propeller - train-propeller -
> + build-optimized".
> +
> +#. Propeller requires LLVM 19 release or later for Clang/Clang++
> + and the linker(ld.lld).
> +
> +#. In addition to LLVM toolchain, Propeller requires a profiling
> + conversion tool: https://github.com/google/autofdo with a release
> + after v0.30.1: https://github.com/google/autofdo/releases/tag/v0.30.1.
> +
> +The Propeller optimization process involves the following steps:
> +
> +#. Initial building: Build the AutoFDO or AutoFDO+ThinLTO binary as
> + you would normally do, but with a set of compile-time / link-time
> + flags, so that a special metadata section is created within the
> + kernel binary. The special section is only intend to be used by the
> + profiling tool, it is not part of the runtime image, nor does it
> + change kernel run time text sections.
> +
> +#. Profiling: The above kernel is then run with a representative
> + workload to gather execution frequency data. This data is collected
> + using hardware sampling, via perf. Propeller is most effective on
> + platforms supporting advanced PMU features like LBR on Intel
> + machines. This step is the same as profiling the kernel for AutoFDO
> + (the exact perf parameters can be different).
> +
> +#. Propeller profile generation: Perf output file is converted to a
> + pair of Propeller profiles via an offline tool.
> +
> +#. Optimized build: Build the AutoFDO or AutoFDO+ThinLTO optimized
> + binary as you would normally do, but with a compile-time /
> + link-time flag to pick up the Propeller compile time and link time
> + profiles. This build step uses 3 profiles - the AutoFDO profile,
> + the Propeller compile-time profile and the Propeller link-time
> + profile.
> +
> +#. Deployment: The optimized kernel binary is deployed and used
> + in production environments, providing improved performance
> + and reduced latency.
> +
> +Preparation
> +===========
> +
> +Configure the kernel with::
> +
> + CONFIG_AUTOFDO_CLANG=y
> + CONFIG_PROPELLER_CLANG=y
> +
> +Customization
> +=============
> +
> +The default CONFIG_PROPELLER_CLANG setting covers kernel space objects
> +for Propeller builds. One can, however, enable or disable Propeller build
> +for individual files and directories by adding a line similar to the
> +following to the respective kernel Makefile:
> +
> +- For enabling a single file (e.g. foo.o)::
> +
> + PROPELLER_PROFILE_foo.o := y
> +
> +- For enabling all files in one directory::
> +
> + PROPELLER_PROFILE := y
> +
> +- For disabling one file::
> +
> + PROPELLER_PROFILE_foo.o := n
> +
> +- For disabling all files in one directory::
> +
> + PROPELLER__PROFILE := n
> +
> +
> +Workflow
> +========
> +
> +Here is an example workflow for building an AutoFDO+Propeller kernel:
> +
> +1) Assuming an AutoFDO profile is already collected following
> + instructions in the AutoFDO document, build the kernel on the host
> + machine, with AutoFDO and Propeller build configs ::
> +
> + CONFIG_AUTOFDO_CLANG=y
> + CONFIG_PROPELLER_CLANG=y
> +
> + and ::
> +
> + $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo-profile-name>
> +
> +2) Install the kernel on the test machine.
> +
> +3) Run the load tests. The '-c' option in perf specifies the sample
> + event period. We suggest using a suitable prime number, like 500009,
> + for this purpose.
> +
> + - For Intel platforms::
> +
> + $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c <count> -o <perf_file> -- <loadtest>
> +
> + - For AMD platforms::
> +
> + $ perf record --pfm-event RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c <count> -o <perf_file> -- <loadtest>
> +
> + Note you can repeat the above steps to collect multiple <perf_file>s.
> +
> +4) (Optional) Download the raw perf file(s) to the host machine.
> +
> +5) Use the create_llvm_prof tool (https://github.com/google/autofdo) to
> + generate Propeller profile. ::
> +
> + $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file>
> + --format=propeller --propeller_output_module_name
> + --out=<propeller_profile_prefix>_cc_profile.txt
> + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt
Prevously I am using perf-6.8.5-0.hs1.hsx.el9.x86_64 and it works fine.
Now in my system, the perf is upgraded to 6.12.gadc218676eef
[root@twshared7248.15.atn5 ~]# perf --version
perf version 6.12.gadc218676eef
and create_llvm_prof does not work any more.
The command to collect sampling data:
# perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c 500009 -- stress --cpu 36 --io 36 --vm 36 --vm-bytes 128M --timeout 300s
stress: info: [536354] dispatching hogs: 36 cpu, 36 io, 36 vm, 0 hdd
stress: info: [536354] successful run completed in 300s
[ perf record: Woken up 2210 times to write data ]
[ perf record: Captured and wrote 562.529 MB perf.data (701971 samples) ]
# uname -r
6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39
The kernel is a 6.11 lto kernel.
I then run the following command:
$ cat ../run.sh
# perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c 500009 \
# -- stress --cpu 36 --io 36 --vm 36 --vm-bytes 128M --timeout 300s
# good: perf-6.8.5-0.hs1.hsx.el9.x86_64
# <propeller_profile_prefix>: /tmp/propeller
./create_llvm_prof --binary=vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39 \
--profile=perf.data \
--format=propeller --propeller_output_module_name \
--out=/tmp/propeller_cc_profile.txt \
--propeller_symorder=/tmp/propeller_ld_profile.txt
$ ./run.sh
WARNING: Logging before InitGoogleLogging() is written to STDERR
I20241212 13:12:18.401772 463318 llvm_propeller_binary_content.cc:376] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is PIE: 0
I20241212 13:12:18.403692 463318 llvm_propeller_binary_content.cc:380] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is relocatable: 0
I20241212 13:12:18.404873 463318 llvm_propeller_binary_content.cc:388] Build Id found in 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39': eaacd5a14abc48cf832b3ad0fa6c64635ab569a8
I20241212 13:12:18.521499 463318 llvm_propeller_binary_content.cc:376] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is PIE: 0
I20241212 13:12:18.521530 463318 llvm_propeller_binary_content.cc:380] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is relocatable: 0
I20241212 13:12:18.521553 463318 llvm_propeller_binary_content.cc:388] Build Id found in 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39': eaacd5a14abc48cf832b3ad0fa6c64635ab569a8
I20241212 13:12:18.521611 463318 llvm_propeller_perf_lbr_aggregator.cc:51] Parsing [1/1] perf.data ...
[ERROR:/home/runner/work/autofdo/autofdo/third_party/perf_data_converter/src/quipper/perf_reader.cc:1386] Event size 132 after uint64_t alignment of the filename length is greater than event size 128 reported by perf for the buildid event of type 0
W20241212 13:12:18.521708 463318 llvm_propeller_perf_lbr_aggregator.cc:55] Skipped profile [1/1] perf.data: FAILED_PRECONDITION: Failed to read perf data file: [1/1] perf.data
W20241212 13:12:18.521718 463318 llvm_propeller_perf_lbr_aggregator.cc:67] Too few branch records in perf data.
E20241212 13:12:18.554437 463318 create_llvm_prof.cc:238] FAILED_PRECONDITION: No perf file is parsed, cannot proceed.
Could you help take a look why perf 12 does not work with create_llvm_prof?
The create_llvm_prof is downloaded from https://github.com/google/autofdo/releases/tag/v0.30.1.
> +
> + "<propeller_profile_prefix>" can be something like "/home/user/dir/any_string".
> +
> + This command generates a pair of Propeller profiles:
> + "<propeller_profile_prefix>_cc_profile.txt" and
> + "<propeller_profile_prefix>_ld_profile.txt".
> +
> + If there are more than 1 perf_file collected in the previous step,
> + you can create a temp list file "<perf_file_list>" with each line
> + containing one perf file name and run::
> +
> + $ create_llvm_prof --binary=<vmlinux> --profile=@<perf_file_list>
> + --format=propeller --propeller_output_module_name
> + --out=<propeller_profile_prefix>_cc_profile.txt
> + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt
> +
> +6) Rebuild the kernel using the AutoFDO and Propeller
> + profiles. ::
> +
> + CONFIG_AUTOFDO_CLANG=y
> + CONFIG_PROPELLER_CLANG=y
> +
> + and ::
> +
> + $ make LLVM=1 CLANG_AUTOFDO_PROFILE=<profile_file> CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d6ea49433747a..42e3af0791e15 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -18449,6 +18449,13 @@ S: Maintained
> F: include/linux/psi*
> F: kernel/sched/psi.c
>
[...]
On Thu, Dec 12, 2024 at 01:20:46PM -0800, Yonghong Song wrote: ... > > +5) Use the create_llvm_prof tool (https://github.com/google/autofdo) to > > + generate Propeller profile. :: > > + > > + $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> > > + --format=propeller --propeller_output_module_name > > + --out=<propeller_profile_prefix>_cc_profile.txt > > + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt > > Prevously I am using perf-6.8.5-0.hs1.hsx.el9.x86_64 and it works fine. > Now in my system, the perf is upgraded to 6.12.gadc218676eef > > [root@twshared7248.15.atn5 ~]# perf --version > perf version 6.12.gadc218676eef > > and create_llvm_prof does not work any more. > > The command to collect sampling data: > > # perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c 500009 -- stress --cpu 36 --io 36 --vm 36 --vm-bytes 128M --timeout 300s > stress: info: [536354] dispatching hogs: 36 cpu, 36 io, 36 vm, 0 hdd > stress: info: [536354] successful run completed in 300s > [ perf record: Woken up 2210 times to write data ] > [ perf record: Captured and wrote 562.529 MB perf.data (701971 samples) ] > # uname -r > 6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39 > > The kernel is a 6.11 lto kernel. > > I then run the following command: > $ cat ../run.sh > # perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c 500009 \ > # -- stress --cpu 36 --io 36 --vm 36 --vm-bytes 128M --timeout 300s > # good: perf-6.8.5-0.hs1.hsx.el9.x86_64 > > # <propeller_profile_prefix>: /tmp/propeller > ./create_llvm_prof --binary=vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39 \ > --profile=perf.data \ > --format=propeller --propeller_output_module_name \ > --out=/tmp/propeller_cc_profile.txt \ > --propeller_symorder=/tmp/propeller_ld_profile.txt > > $ ./run.sh > WARNING: Logging before InitGoogleLogging() is written to STDERR > I20241212 13:12:18.401772 463318 llvm_propeller_binary_content.cc:376] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is PIE: 0 > I20241212 13:12:18.403692 463318 llvm_propeller_binary_content.cc:380] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is relocatable: 0 > I20241212 13:12:18.404873 463318 llvm_propeller_binary_content.cc:388] Build Id found in 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39': eaacd5a14abc48cf832b3ad0fa6c64635ab569a8 > I20241212 13:12:18.521499 463318 llvm_propeller_binary_content.cc:376] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is PIE: 0 > I20241212 13:12:18.521530 463318 llvm_propeller_binary_content.cc:380] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is relocatable: 0 > I20241212 13:12:18.521553 463318 llvm_propeller_binary_content.cc:388] Build Id found in 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39': eaacd5a14abc48cf832b3ad0fa6c64635ab569a8 > I20241212 13:12:18.521611 463318 llvm_propeller_perf_lbr_aggregator.cc:51] Parsing [1/1] perf.data ... > [ERROR:/home/runner/work/autofdo/autofdo/third_party/perf_data_converter/src/quipper/perf_reader.cc:1386] Event size 132 after uint64_t alignment of the filename length is greater than event size 128 reported by perf for the buildid event of type 0 > W20241212 13:12:18.521708 463318 llvm_propeller_perf_lbr_aggregator.cc:55] Skipped profile [1/1] perf.data: FAILED_PRECONDITION: Failed to read perf data file: [1/1] perf.data > W20241212 13:12:18.521718 463318 llvm_propeller_perf_lbr_aggregator.cc:67] Too few branch records in perf data. > E20241212 13:12:18.554437 463318 create_llvm_prof.cc:238] FAILED_PRECONDITION: No perf file is parsed, cannot proceed. > > > Could you help take a look why perf 12 does not work with create_llvm_prof? > The create_llvm_prof is downloaded from https://github.com/google/autofdo/releases/tag/v0.30.1. I think Peter may have reported the same issue on GitHub? https://github.com/google/autofdo/issues/233 I wonder if this is a kernel side or perf tool regression? Cheers, Nathan
We will take a look at this issue and get back to you. Thanks for reporting this. Best Regards, -Rong On Thu, Dec 12, 2024 at 1:34 PM Nathan Chancellor <nathan@kernel.org> wrote: > > On Thu, Dec 12, 2024 at 01:20:46PM -0800, Yonghong Song wrote: > ... > > > +5) Use the create_llvm_prof tool (https://github.com/google/autofdo) to > > > + generate Propeller profile. :: > > > + > > > + $ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> > > > + --format=propeller --propeller_output_module_name > > > + --out=<propeller_profile_prefix>_cc_profile.txt > > > + --propeller_symorder=<propeller_profile_prefix>_ld_profile.txt > > > > Prevously I am using perf-6.8.5-0.hs1.hsx.el9.x86_64 and it works fine. > > Now in my system, the perf is upgraded to 6.12.gadc218676eef > > > > [root@twshared7248.15.atn5 ~]# perf --version > > perf version 6.12.gadc218676eef > > > > and create_llvm_prof does not work any more. > > > > The command to collect sampling data: > > > > # perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c 500009 -- stress --cpu 36 --io 36 --vm 36 --vm-bytes 128M --timeout 300s > > stress: info: [536354] dispatching hogs: 36 cpu, 36 io, 36 vm, 0 hdd > > stress: info: [536354] successful run completed in 300s > > [ perf record: Woken up 2210 times to write data ] > > [ perf record: Captured and wrote 562.529 MB perf.data (701971 samples) ] > > # uname -r > > 6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39 > > > > The kernel is a 6.11 lto kernel. > > > > I then run the following command: > > $ cat ../run.sh > > # perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c 500009 \ > > # -- stress --cpu 36 --io 36 --vm 36 --vm-bytes 128M --timeout 300s > > # good: perf-6.8.5-0.hs1.hsx.el9.x86_64 > > > > # <propeller_profile_prefix>: /tmp/propeller > > ./create_llvm_prof --binary=vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39 \ > > --profile=perf.data \ > > --format=propeller --propeller_output_module_name \ > > --out=/tmp/propeller_cc_profile.txt \ > > --propeller_symorder=/tmp/propeller_ld_profile.txt > > > > $ ./run.sh > > WARNING: Logging before InitGoogleLogging() is written to STDERR > > I20241212 13:12:18.401772 463318 llvm_propeller_binary_content.cc:376] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is PIE: 0 > > I20241212 13:12:18.403692 463318 llvm_propeller_binary_content.cc:380] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is relocatable: 0 > > I20241212 13:12:18.404873 463318 llvm_propeller_binary_content.cc:388] Build Id found in 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39': eaacd5a14abc48cf832b3ad0fa6c64635ab569a8 > > I20241212 13:12:18.521499 463318 llvm_propeller_binary_content.cc:376] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is PIE: 0 > > I20241212 13:12:18.521530 463318 llvm_propeller_binary_content.cc:380] 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39' is relocatable: 0 > > I20241212 13:12:18.521553 463318 llvm_propeller_binary_content.cc:388] Build Id found in 'vmlinux-6.11.1-0_fbk0_lto_rc19_612_gb572dfac1b39': eaacd5a14abc48cf832b3ad0fa6c64635ab569a8 > > I20241212 13:12:18.521611 463318 llvm_propeller_perf_lbr_aggregator.cc:51] Parsing [1/1] perf.data ... > > [ERROR:/home/runner/work/autofdo/autofdo/third_party/perf_data_converter/src/quipper/perf_reader.cc:1386] Event size 132 after uint64_t alignment of the filename length is greater than event size 128 reported by perf for the buildid event of type 0 > > W20241212 13:12:18.521708 463318 llvm_propeller_perf_lbr_aggregator.cc:55] Skipped profile [1/1] perf.data: FAILED_PRECONDITION: Failed to read perf data file: [1/1] perf.data > > W20241212 13:12:18.521718 463318 llvm_propeller_perf_lbr_aggregator.cc:67] Too few branch records in perf data. > > E20241212 13:12:18.554437 463318 create_llvm_prof.cc:238] FAILED_PRECONDITION: No perf file is parsed, cannot proceed. > > > > > > Could you help take a look why perf 12 does not work with create_llvm_prof? > > The create_llvm_prof is downloaded from https://github.com/google/autofdo/releases/tag/v0.30.1. > > I think Peter may have reported the same issue on GitHub? > > https://github.com/google/autofdo/issues/233 > > I wonder if this is a kernel side or perf tool regression? > > Cheers, > Nathan
Hi Rong, On Sat, Nov 02, 2024 at 10:51:14AM -0700, Rong Xu wrote: > diff --git a/scripts/Makefile.propeller b/scripts/Makefile.propeller > new file mode 100644 > index 0000000000000..344190717e471 > --- /dev/null > +++ b/scripts/Makefile.propeller > @@ -0,0 +1,28 @@ > +# SPDX-License-Identifier: GPL-2.0 > + > +# Enable available and selected Clang Propeller features. > +ifdef CLANG_PROPELLER_PROFILE_PREFIX > + CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=list=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt -ffunction-sections > + KBUILD_LDFLAGS += --symbol-ordering-file=$(CLANG_PROPELLER_PROFILE_PREFIX)_ld_profile.txt --no-warn-symbol-ordering > +else > + CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=labels > +endif It appears that '-fbasic-block-sections=labels' has been deprecated in the main branch of LLVM, as I see a warning repeated over and over when building allmodconfig: clang: warning: argument '-fbasic-block-sections=labels' is deprecated, use '-fbasic-block-address-map' instead [-Wdeprecated] https://github.com/llvm/llvm-project/commit/7b7747dc1d3da1a829503ea9505b4cecce4f5bda Sorry that I missed this during testing, as I was only using clang-19 at the time. I think you can send a fixup on top of Masahiro's branch: https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/log/?h=kbuild > +# Propeller requires debug information to embed module names in the profiles. > +# If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. Skip this for AutoFDO, > +# as the option should already be set. > +ifndef CONFIG_DEBUG_INFO > + ifndef CONFIG_AUTOFDO_CLANG > + CFLAGS_PROPELLER_CLANG += -gmlt > + endif > +endif > + > +ifdef CONFIG_LTO_CLANG_THIN > + ifdef CLANG_PROPELLER_PROFILE_PREFIX > + KBUILD_LDFLAGS += --lto-basic-block-sections=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt > + else > + KBUILD_LDFLAGS += --lto-basic-block-sections=labels I think this might have a similar problem but I have not tested. > + endif > +endif > + > +export CFLAGS_PROPELLER_CLANG Cheers, Nathan
Thanks Nathan for finding this out! We changed the propeller option with this patch: https://github.com/llvm/llvm-project/pull/110039 Currently, this patch is only in the ToT clang (v20) and not yet released in v19. I'll add a compiler version check to the patch: if the clang version >= 20, use the new option. If this patch is later released in v19.x clang, I'll have to update the check accordingly. If I don't hear objections, I'll send a fixup on top of Masahiro's branch. Thanks, -Rong On Thu, Nov 7, 2024 at 12:45 PM Nathan Chancellor <nathan@kernel.org> wrote: > > Hi Rong, > > On Sat, Nov 02, 2024 at 10:51:14AM -0700, Rong Xu wrote: > > diff --git a/scripts/Makefile.propeller b/scripts/Makefile.propeller > > new file mode 100644 > > index 0000000000000..344190717e471 > > --- /dev/null > > +++ b/scripts/Makefile.propeller > > @@ -0,0 +1,28 @@ > > +# SPDX-License-Identifier: GPL-2.0 > > + > > +# Enable available and selected Clang Propeller features. > > +ifdef CLANG_PROPELLER_PROFILE_PREFIX > > + CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=list=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt -ffunction-sections > > + KBUILD_LDFLAGS += --symbol-ordering-file=$(CLANG_PROPELLER_PROFILE_PREFIX)_ld_profile.txt --no-warn-symbol-ordering > > +else > > + CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=labels > > +endif > > It appears that '-fbasic-block-sections=labels' has been deprecated in > the main branch of LLVM, as I see a warning repeated over and over when > building allmodconfig: > > clang: warning: argument '-fbasic-block-sections=labels' is deprecated, use '-fbasic-block-address-map' instead [-Wdeprecated] > > https://github.com/llvm/llvm-project/commit/7b7747dc1d3da1a829503ea9505b4cecce4f5bda > > Sorry that I missed this during testing, as I was only using clang-19 at > the time. > > I think you can send a fixup on top of Masahiro's branch: > > https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/log/?h=kbuild > > > +# Propeller requires debug information to embed module names in the profiles. > > +# If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. Skip this for AutoFDO, > > +# as the option should already be set. > > +ifndef CONFIG_DEBUG_INFO > > + ifndef CONFIG_AUTOFDO_CLANG > > + CFLAGS_PROPELLER_CLANG += -gmlt > > + endif > > +endif > > + > > +ifdef CONFIG_LTO_CLANG_THIN > > + ifdef CLANG_PROPELLER_PROFILE_PREFIX > > + KBUILD_LDFLAGS += --lto-basic-block-sections=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt > > + else > > + KBUILD_LDFLAGS += --lto-basic-block-sections=labels > > I think this might have a similar problem but I have not tested. > > > + endif > > +endif > > + > > +export CFLAGS_PROPELLER_CLANG > > Cheers, > Nathan
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