Re: [PATCH v2 4/5] kernel hacking: new config DEBUG_EXPERIENCE to apply GCC -Og optimization

From: Randy Dunlap <rdunlap@infradead.org>
To: "Du, Changbin" <changbin.du@intel.com>,
	Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	yamada.masahiro@socionext.com, michal.lkml@markovi.net,
	tglx@linutronix.de, mingo@redhat.com, x86@kernel.org,
	lgirdwood@gmail.com, broonie@kernel.org, arnd@arndb.de,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arch@vger.kernel.org
Subject: Re: [PATCH v2 4/5] kernel hacking: new config DEBUG_EXPERIENCE to apply GCC -Og optimization
Date: Sat, 5 May 2018 17:27:06 -0700	[thread overview]
Message-ID: <9dc6279b-767a-a4b1-75a9-aefdef61a224@infradead.org> (raw)
In-Reply-To: <20180505235725.hglh6u77spw55qa5@intel.com>

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.
-- 
~Randy