| Message ID | 1525268700-10631-5-git-send-email-changbin.du@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, 2 May 2018 21:44:59 +0800 changbin.du@intel.com wrote: > From: Changbin Du <changbin.du@intel.com> > > This will apply GCC '-Og' optimization level which is supported > since GCC 4.8. This optimization level offers a reasonable level > of optimization while maintaining fast compilation and a good > debugging experience. It is similar to '-O1' while perfer keeping > debug ability over runtime speed. > > If enabling this option breaks your kernel, you should either > disable this or find a fix (mostly in the arch code). Currently > this option has only be tested on x86_64 platform. If this becomes an issue, you probably need to add an arch config that it depends on like CONFIG_HAVE_DEBUG_EXPERIENCE (or another name, as I mention below). > > This option can satisfy people who was searching for a method > to disable compiler optimizations so to achieve better kernel > debugging experience with kgdb or qemu. > > The main problem of '-Og' is we must not use __attribute__((error(msg))). > The compiler will report error though the call to error function > still can be optimize out. So we must fallback to array tricky. > > Comparison of vmlinux size: a bit smaller. > > w/o CONFIG_DEBUG_EXPERIENCE I hate the config name. I probably can't come up with better ones but let's try: CONFIG_DEBUG_OPTIMIZE ? CONFIG_OPTIMIZE_DEBUG ? But "EXPERIENCE" sounds like I'm on some DEBUG LSD. > $ size vmlinux > text data bss dec hex filename > 22665554 9709674 2920908 35296136 21a9388 vmlinux > > w/ CONFIG_DEBUG_EXPERIENCE > $ size vmlinux > text data bss dec hex filename > 21499032 10102758 2920908 34522698 20ec64a vmlinux > > Comparison of system performance: a bit drop (~6%). > This benchmark of kernel compilation is suggested by Ingo Molnar. > https://lkml.org/lkml/2018/5/2/74 > > Preparation: Set cpufreq to 'performance'. > for ((cpu=0; cpu<120; cpu++)); do > G=/sys/devices/system/cpu/cpu$cpu/cpufreq/scaling_governor > [ -f $G ] && echo performance > $G > done > > w/o CONFIG_DEBUG_EXPERIENCE > $ perf stat --repeat 5 --null --pre '\ > cp -a kernel ../kernel.copy.$(date +%s); \ > rm -rf *; \ > git checkout .; \ > echo 1 > /proc/sys/vm/drop_caches; \ > find ../kernel* -type f | xargs cat >/dev/null; \ > make -j kernel >/dev/null; \ > make clean >/dev/null 2>&1; \ > sync '\ > \ > make -j8 >/dev/null > > Performance counter stats for 'make -j8' (5 runs): > > 219.764246652 seconds time elapsed ( +- 0.78% ) > > w/ CONFIG_DEBUG_EXPERIENCE > $ perf stat --repeat 5 --null --pre '\ > cp -a kernel ../kernel.copy.$(date +%s); \ > rm -rf *; \ > git checkout .; \ > echo 1 > /proc/sys/vm/drop_caches; \ > find ../kernel* -type f | xargs cat >/dev/null; \ > make -j kernel >/dev/null; \ > make clean >/dev/null 2>&1; \ > sync '\ > \ > make -j8 >/dev/null > > Performance counter stats for 'make -j8' (5 runs): > > 233.574187771 seconds time elapsed ( +- 0.19% ) > > Signed-off-by: Changbin Du <changbin.du@intel.com> > > --- > v2: > o Improve performance benchmark as suggested by Ingo. > o Grammar updates in description. (Randy Dunlap) > --- > Makefile | 4 ++++ > include/linux/compiler-gcc.h | 2 +- > include/linux/compiler.h | 2 +- > lib/Kconfig.debug | 21 +++++++++++++++++++++ > 4 files changed, 27 insertions(+), 2 deletions(-) > > diff --git a/Makefile b/Makefile > index eb694f6..6a10469 100644 > --- a/Makefile > +++ b/Makefile > @@ -639,6 +639,9 @@ KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation) > KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow) > KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context) > > +ifdef CONFIG_DEBUG_EXPERIENCE > +KBUILD_CFLAGS += $(call cc-option, -Og) > +else > ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE > KBUILD_CFLAGS += $(call cc-option,-Oz,-Os) > KBUILD_CFLAGS += $(call cc-disable-warning,maybe-uninitialized,) > @@ -649,6 +652,7 @@ else > KBUILD_CFLAGS += -O2 > endif > endif > +endif > > KBUILD_CFLAGS += $(call cc-ifversion, -lt, 0409, \ > $(call cc-disable-warning,maybe-uninitialized,)) > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h > index b4bf73f..b8b3832 100644 > --- a/include/linux/compiler-gcc.h > +++ b/include/linux/compiler-gcc.h > @@ -192,7 +192,7 @@ > > #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) > > -#ifndef __CHECKER__ > +#if !defined(__CHECKER__) && !defined(CONFIG_DEBUG_EXPERIENCE) > # define __compiletime_warning(message) __attribute__((warning(message))) > # define __compiletime_error(message) __attribute__((error(message))) > #endif /* __CHECKER__ */ > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index ab4711c..952cc7f 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -301,7 +301,7 @@ unsigned long read_word_at_a_time(const void *addr) > * sparse see a constant array size without breaking compiletime_assert on old > * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether. > */ > -# ifndef __CHECKER__ > +# if !defined(__CHECKER__) && !defined(CONFIG_DEBUG_EXPERIENCE) > # define __compiletime_error_fallback(condition) \ > do { ((void)sizeof(char[1 - 2 * condition])); } while (0) > # endif > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index ab55801..e264199 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -216,6 +216,27 @@ config NO_AUTO_INLINE > > If unsure, select N. > > +config DEBUG_EXPERIENCE > + bool "Optimize for better debugging experience (-Og)" > + default n You don't need to add "default n" because that's the default if it isn't specified. -- Steve > + select NO_AUTO_INLINE > + depends on !CC_OPTIMIZE_FOR_SIZE > + help > + This will apply GCC '-Og' optimization level which is supported > + since GCC 4.8. This optimization level offers a reasonable level > + of optimization while maintaining fast compilation and a good > + debugging experience. It is similar to '-O1' while preferring to > + keep debug ability over runtime speed. The overall performance > + will drop a bit (~6%). > + > + Use only if you want to debug the kernel, especially if you want > + to have better kernel debugging experience with gdb facilities > + like kgdb or qemu. If enabling this option breaks your kernel, > + you should either disable this or find a fix (mostly in the arch > + code). Currently this option has only be tested on x86_64 platform. > + > + If unsure, select N. > + > config ENABLE_WARN_DEPRECATED > bool "Enable __deprecated logic" > default y -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 05/02/2018 06:44 AM, changbin.du@intel.com wrote: > From: Changbin Du <changbin.du@intel.com> > Sorry, I missed one: > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index ab55801..e264199 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -216,6 +216,27 @@ config NO_AUTO_INLINE > > If unsure, select N. > > +config DEBUG_EXPERIENCE > + bool "Optimize for better debugging experience (-Og)" > + default n > + select NO_AUTO_INLINE > + depends on !CC_OPTIMIZE_FOR_SIZE > + help > + This will apply GCC '-Og' optimization level which is supported > + since GCC 4.8. This optimization level offers a reasonable level > + of optimization while maintaining fast compilation and a good > + debugging experience. It is similar to '-O1' while preferring to > + keep debug ability over runtime speed. The overall performance > + will drop a bit (~6%). > + > + Use only if you want to debug the kernel, especially if you want > + to have better kernel debugging experience with gdb facilities > + like kgdb or qemu. If enabling this option breaks your kernel, > + you should either disable this or find a fix (mostly in the arch > + code). Currently this option has only be tested on x86_64 platform. been tested > + > + If unsure, select N. > + > config ENABLE_WARN_DEPRECATED > bool "Enable __deprecated logic" > default y >
On Wed, 2 May 2018 10:17:07 -0400 Steven Rostedt <rostedt@goodmis.org> wrote: > > Comparison of vmlinux size: a bit smaller. > > > > w/o CONFIG_DEBUG_EXPERIENCE > > I hate the config name. > > I probably can't come up with better ones but let's try: > > CONFIG_DEBUG_OPTIMIZE ? > CONFIG_OPTIMIZE_DEBUG ? > > But "EXPERIENCE" sounds like I'm on some DEBUG LSD. Metoo, but the gcc people decided on "-Og: Optimize debugging experience ..." and I think there are benefits if the kernel is to align the naming with that. -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 2 May 2018 13:45:58 -0700 Andrew Morton <akpm@linux-foundation.org> wrote: > On Wed, 2 May 2018 10:17:07 -0400 Steven Rostedt <rostedt@goodmis.org> wrote: > > > > Comparison of vmlinux size: a bit smaller. > > > > > > w/o CONFIG_DEBUG_EXPERIENCE > > > > I hate the config name. > > > > I probably can't come up with better ones but let's try: > > > > CONFIG_DEBUG_OPTIMIZE ? > > CONFIG_OPTIMIZE_DEBUG ? > > > > But "EXPERIENCE" sounds like I'm on some DEBUG LSD. > > Metoo, but the gcc people decided on "-Og: Optimize debugging > experience ..." and I think there are benefits if the kernel is to > align the naming with that. I still see that as "Optimize debugging" and "experience" is just the platform of what was done. With that gcc comment, I still think CONFIG_OPTIMIZE_DEBUG is more inline with what it is and understandable than CONFIG_DEBUG_EXPERIENCE. The "OPTIMIZE" is the key word there. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, May 02, 2018 at 09:19:56PM -0400, Steven Rostedt wrote: > On Wed, 2 May 2018 13:45:58 -0700 > Andrew Morton <akpm@linux-foundation.org> wrote: > > > On Wed, 2 May 2018 10:17:07 -0400 Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > > Comparison of vmlinux size: a bit smaller. > > > > > > > > w/o CONFIG_DEBUG_EXPERIENCE > > > > > > I hate the config name. > > > > > > I probably can't come up with better ones but let's try: > > > > > > CONFIG_DEBUG_OPTIMIZE ? > > > CONFIG_OPTIMIZE_DEBUG ? > > > > > > But "EXPERIENCE" sounds like I'm on some DEBUG LSD. > > > > Metoo, but the gcc people decided on "-Og: Optimize debugging > > experience ..." and I think there are benefits if the kernel is to > > align the naming with that. > > I still see that as "Optimize debugging" and "experience" is just the > platform of what was done. > > With that gcc comment, I still think CONFIG_OPTIMIZE_DEBUG is more > inline with what it is and understandable than > CONFIG_DEBUG_EXPERIENCE. The "OPTIMIZE" is the key word there. > > -- Steve What about CONFIG_CC_OPTIMIZE_FOR_DEBUGGING? We alreay have CONFIG_CC_OPTIMIZE_FOR_SIZE and CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE. And do we need to move it to existing configuration menu "General setup-> Compiler optimization level"? But I also want it appear in "kernel hacking" since this is a debug option.
On Thu, 3 May 2018 21:45:46 +0800 "Du, Changbin" <changbin.du@intel.com> wrote: > > With that gcc comment, I still think CONFIG_OPTIMIZE_DEBUG is more > > inline with what it is and understandable than > > CONFIG_DEBUG_EXPERIENCE. The "OPTIMIZE" is the key word there. > > > > -- Steve > What about CONFIG_CC_OPTIMIZE_FOR_DEBUGGING? We alreay have > CONFIG_CC_OPTIMIZE_FOR_SIZE and CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE. Yes I like that much better. > > And do we need to move it to existing configuration menu "General setup-> > Compiler optimization level"? But I also want it appear in "kernel hacking" > since this is a debug option. I understand why you would want it by debugging, but I think it does make more sense to be included with the above two other options, as they are all mutually exclusive. This brings up the topic of creating config paradigms. That is, a way of saying "I want a debug kernel" and select one option that selects everything you would expect. Or perhaps we should have a: make debug_config that does it. But that's a different topic. For now, I would just included it in init/Kconfig, and not worry about it not showing up in kernel hacking. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, May 03, 2018 at 10:28:23AM -0400, Steven Rostedt wrote: > On Thu, 3 May 2018 21:45:46 +0800 > "Du, Changbin" <changbin.du@intel.com> wrote: > > > > With that gcc comment, I still think CONFIG_OPTIMIZE_DEBUG is more > > > inline with what it is and understandable than > > > CONFIG_DEBUG_EXPERIENCE. The "OPTIMIZE" is the key word there. > > > > > > -- Steve > > What about CONFIG_CC_OPTIMIZE_FOR_DEBUGGING? We alreay have > > CONFIG_CC_OPTIMIZE_FOR_SIZE and CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE. > > Yes I like that much better. > > > > > And do we need to move it to existing configuration menu "General setup-> > > Compiler optimization level"? But I also want it appear in "kernel hacking" > > since this is a debug option. > > I understand why you would want it by debugging, but I think it does > make more sense to be included with the above two other options, as > they are all mutually exclusive. > > This brings up the topic of creating config paradigms. That is, a way > of saying "I want a debug kernel" and select one option that selects > everything you would expect. Or perhaps we should have a: > > make debug_config > Agree, I accomplish this by running script scripts/kconfig/merge_config.sh. > that does it. > > But that's a different topic. For now, I would just included it in > init/Kconfig, and not worry about it not showing up in kernel hacking. > > > -- Steve
On 05/05/2018 04:57 PM, Du, Changbin wrote: > On Thu, May 03, 2018 at 10:28:23AM -0400, Steven Rostedt wrote: >> On Thu, 3 May 2018 21:45:46 +0800 >> "Du, Changbin" <changbin.du@intel.com> wrote: >> >>>> With that gcc comment, I still think CONFIG_OPTIMIZE_DEBUG is more >>>> inline with what it is and understandable than >>>> CONFIG_DEBUG_EXPERIENCE. The "OPTIMIZE" is the key word there. >>>> >>>> -- Steve >>> What about CONFIG_CC_OPTIMIZE_FOR_DEBUGGING? We alreay have >>> CONFIG_CC_OPTIMIZE_FOR_SIZE and CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE. >> >> Yes I like that much better. >> >>> >>> And do we need to move it to existing configuration menu "General setup-> >>> Compiler optimization level"? But I also want it appear in "kernel hacking" >>> since this is a debug option. >> >> I understand why you would want it by debugging, but I think it does >> make more sense to be included with the above two other options, as >> they are all mutually exclusive. mm, sounds good. >> This brings up the topic of creating config paradigms. That is, a way >> of saying "I want a debug kernel" and select one option that selects >> everything you would expect. Or perhaps we should have a: >> >> make debug_config Sometimes I want to build allmodconfig-minus-debug options ... but not all debug options. I still want debugfs but most options that end with _DEBUG are disabled. I.e., I don't want the options that cause big run-time slowdowns. (unless I cause that by printing some debugfs contents) Can merge_config.sh (or one of its cousins) help with that? > Agree, I accomplish this by running script scripts/kconfig/merge_config.sh. > >> that does it. >> >> But that's a different topic. For now, I would just included it in >> init/Kconfig, and not worry about it not showing up in kernel hacking. Ack. thanks.
diff --git a/Makefile b/Makefile index eb694f6..6a10469 100644 --- a/Makefile +++ b/Makefile @@ -639,6 +639,9 @@ KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation) KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow) KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context) +ifdef CONFIG_DEBUG_EXPERIENCE +KBUILD_CFLAGS += $(call cc-option, -Og) +else ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE KBUILD_CFLAGS += $(call cc-option,-Oz,-Os) KBUILD_CFLAGS += $(call cc-disable-warning,maybe-uninitialized,) @@ -649,6 +652,7 @@ else KBUILD_CFLAGS += -O2 endif endif +endif KBUILD_CFLAGS += $(call cc-ifversion, -lt, 0409, \ $(call cc-disable-warning,maybe-uninitialized,)) diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index b4bf73f..b8b3832 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -192,7 +192,7 @@ #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) -#ifndef __CHECKER__ +#if !defined(__CHECKER__) && !defined(CONFIG_DEBUG_EXPERIENCE) # define __compiletime_warning(message) __attribute__((warning(message))) # define __compiletime_error(message) __attribute__((error(message))) #endif /* __CHECKER__ */ diff --git a/include/linux/compiler.h b/include/linux/compiler.h index ab4711c..952cc7f 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -301,7 +301,7 @@ unsigned long read_word_at_a_time(const void *addr) * sparse see a constant array size without breaking compiletime_assert on old * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether. */ -# ifndef __CHECKER__ +# if !defined(__CHECKER__) && !defined(CONFIG_DEBUG_EXPERIENCE) # define __compiletime_error_fallback(condition) \ do { ((void)sizeof(char[1 - 2 * condition])); } while (0) # endif diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index ab55801..e264199 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -216,6 +216,27 @@ config NO_AUTO_INLINE If unsure, select N. +config DEBUG_EXPERIENCE + bool "Optimize for better debugging experience (-Og)" + default n + select NO_AUTO_INLINE + depends on !CC_OPTIMIZE_FOR_SIZE + help + This will apply GCC '-Og' optimization level which is supported + since GCC 4.8. This optimization level offers a reasonable level + of optimization while maintaining fast compilation and a good + debugging experience. It is similar to '-O1' while preferring to + keep debug ability over runtime speed. The overall performance + will drop a bit (~6%). + + Use only if you want to debug the kernel, especially if you want + to have better kernel debugging experience with gdb facilities + like kgdb or qemu. If enabling this option breaks your kernel, + you should either disable this or find a fix (mostly in the arch + code). Currently this option has only be tested on x86_64 platform. + + If unsure, select N. + config ENABLE_WARN_DEPRECATED bool "Enable __deprecated logic" default y