[v3,2/4] kernel hacking: new config NO_AUTO_INLINE to disable compiler auto-inline optimizations
diff mbox series

Message ID 20181028130945.23581-3-changbin.du@gmail.com
State New
Headers show
Series
  • kernel hacking: GCC optimization for better debug experience (-Og)
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Commit Message

Changbin Du Oct. 28, 2018, 1:09 p.m. UTC
This patch add a new kernel hacking option NO_AUTO_INLINE. Selecting
this option will prevent the compiler from optimizing the kernel by
auto-inlining functions not marked with the inline keyword.

With this option, only functions explicitly marked with "inline" will
be inlined. This will allow the function tracer to trace more functions
because it only traces functions that the compiler has not inlined.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 Makefile          |  6 ++++++
 lib/Kconfig.debug | 17 +++++++++++++++++
 2 files changed, 23 insertions(+)

Comments

Masahiro Yamada Oct. 29, 2018, 1:03 p.m. UTC | #1
On Sun, Oct 28, 2018 at 10:13 PM Changbin Du <changbin.du@gmail.com> wrote:
>
> This patch add a new kernel hacking option NO_AUTO_INLINE. Selecting


I fixed "This patch add ..." to "This patch adds ..."
then applied to linux-kbuild.




> this option will prevent the compiler from optimizing the kernel by
> auto-inlining functions not marked with the inline keyword.
>
> With this option, only functions explicitly marked with "inline" will
> be inlined. This will allow the function tracer to trace more functions
> because it only traces functions that the compiler has not inlined.
>
> Signed-off-by: Changbin Du <changbin.du@gmail.com>
> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
>  Makefile          |  6 ++++++
>  lib/Kconfig.debug | 17 +++++++++++++++++
>  2 files changed, 23 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index 7d4ba5196010..04beb822ddfc 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -749,6 +749,12 @@ KBUILD_CFLAGS      += $(call cc-option, -femit-struct-debug-baseonly) \
>                    $(call cc-option,-fno-var-tracking)
>  endif
>
> +ifdef CONFIG_NO_AUTO_INLINE
> +KBUILD_CFLAGS   += $(call cc-option, -fno-inline-functions) \
> +                  $(call cc-option, -fno-inline-small-functions) \
> +                  $(call cc-option, -fno-inline-functions-called-once)
> +endif
> +
>  ifdef CONFIG_FUNCTION_TRACER
>  ifdef CONFIG_FTRACE_MCOUNT_RECORD
>    # gcc 5 supports generating the mcount tables directly
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 04adfc3b185e..d50711b41dad 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -211,6 +211,23 @@ config GDB_SCRIPTS
>           instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
>           for further details.
>
> +config NO_AUTO_INLINE
> +       bool "Disable compiler auto-inline optimizations"
> +       help
> +         This will prevent the compiler from optimizing the kernel by
> +         auto-inlining functions not marked with the inline keyword.
> +         With this option, only functions explicitly marked with
> +         "inline" will be inlined. This will allow the function tracer
> +         to trace more functions because it only traces functions that
> +         the compiler has not inlined.
> +
> +         Enabling this function can help debugging a kernel if using
> +         the function tracer. But it can also change how the kernel
> +         works, because inlining functions may change the timing,
> +         which could make it difficult while debugging race conditions.
> +
> +         If unsure, select N.
> +
>  config ENABLE_MUST_CHECK
>         bool "Enable __must_check logic"
>         default y
> --
> 2.17.1
>

Patch
diff mbox series

diff --git a/Makefile b/Makefile
index 7d4ba5196010..04beb822ddfc 100644
--- a/Makefile
+++ b/Makefile
@@ -749,6 +749,12 @@  KBUILD_CFLAGS 	+= $(call cc-option, -femit-struct-debug-baseonly) \
 		   $(call cc-option,-fno-var-tracking)
 endif
 
+ifdef CONFIG_NO_AUTO_INLINE
+KBUILD_CFLAGS   += $(call cc-option, -fno-inline-functions) \
+		   $(call cc-option, -fno-inline-small-functions) \
+		   $(call cc-option, -fno-inline-functions-called-once)
+endif
+
 ifdef CONFIG_FUNCTION_TRACER
 ifdef CONFIG_FTRACE_MCOUNT_RECORD
   # gcc 5 supports generating the mcount tables directly
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 04adfc3b185e..d50711b41dad 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -211,6 +211,23 @@  config GDB_SCRIPTS
 	  instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
 	  for further details.
 
+config NO_AUTO_INLINE
+	bool "Disable compiler auto-inline optimizations"
+	help
+	  This will prevent the compiler from optimizing the kernel by
+	  auto-inlining functions not marked with the inline keyword.
+	  With this option, only functions explicitly marked with
+	  "inline" will be inlined. This will allow the function tracer
+	  to trace more functions because it only traces functions that
+	  the compiler has not inlined.
+
+	  Enabling this function can help debugging a kernel if using
+	  the function tracer. But it can also change how the kernel
+	  works, because inlining functions may change the timing,
+	  which could make it difficult while debugging race conditions.
+
+	  If unsure, select N.
+
 config ENABLE_MUST_CHECK
 	bool "Enable __must_check logic"
 	default y