linux-kernel - Re: [PATCH 1/1] boot: Put initcall_debug into its own Kconfig option DEBUG

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Date:	Mon, 13 Aug 2012 15:39:54 -0700
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Thai Bui <blquythai@...il.com>
CC:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] boot: Put initcall_debug into its own Kconfig option
 DEBUG_INITCALL

On 08/13/2012 03:08 PM, Thai Bui wrote:
> Hi all,
>
> I am as part of a capstone group at Portland State University is working
> to tinify the kernel as small as possible. The ultimate goal is to make
> the kernel small enough to use on micro-controller (or under < 200k).
> This patch is one of them, it saves 176 bytes on a minimal configuration
> of the kernel (the bzImage file was reduced from 363264 bytes to 363264
> bytes applying this patch).
>
> Aside from the purpose of reducing the size of the kernel. We are also
> trying to clean up the kernel by making Kconfig options to compile out
> the stuffs that aren't used often.

IMO the kernel already has too many kconfig options.

Also, personally I would not merge a patch that saves so little memory,
especially on what I consider a very useful option.


> On Mon, Aug 13, 2012 at 5:21 PM, Konrad Rzeszutek Wilk
> <konrad.wilk@...cle.com <mailto:konrad.wilk@...cle.com>> wrote:
>
>     On Mon, Aug 13, 2012 at 01:57:11PM -0700, Thai Bui wrote:
>      > Putting DEBUG_INITCALL config option to compile out the
>     command-line option
>      > "initcall_debug".
>
>     Can you explain the benfits of this please?
>      >
>      > Signed-off-by: Thai Bui <blquythai@...il.com
>     <mailto:blquythai@...il.com>>
>      > Reviewed-by: Josh Triplett <josh@...htriplett.org
>     <mailto:josh@...htriplett.org>>
>      > ---
>      >  Documentation/kernel-parameters.txt |    3 ++-
>      >  include/linux/init.h                |    4 ++++
>      >  init/main.c                         |    2 ++
>      >  lib/Kconfig.debug                   |    9 +++++++++
>      >  4 files changed, 17 insertions(+), 1 deletion(-)
>      >
>      > diff --git a/Documentation/kernel-parameters.txt
>     b/Documentation/kernel-parameters.txt
>      > index d99fd9c..3dbaf15 100644
>      > --- a/Documentation/kernel-parameters.txt
>      > +++ b/Documentation/kernel-parameters.txt
>      > @@ -1026,7 +1026,8 @@ bytes respectively. Such letter suffixes
>     can also be entirely omitted.
>      >
>      >       initcall_debug  [KNL] Trace initcalls as they are executed.
>       Useful
>      >                       for working out where the kernel is dying
>     during
>      > -                     startup.
>      > +                     startup. DEBUG_INITCALL needs to be enabled
>     in order
>      > +                     for this option to work.
>      >
>      >       initrd=         [BOOT] Specify the location of the initial
>     ramdisk
>      >
>      > diff --git a/include/linux/init.h b/include/linux/init.h
>      > index 6b95109..d2f31f1 100644
>      > --- a/include/linux/init.h
>      > +++ b/include/linux/init.h
>      > @@ -157,7 +157,11 @@ void prepare_namespace(void);
>      >
>      >  extern void (*late_time_init)(void);
>      >
>      > +#ifdef CONFIG_DEBUG_INITCALL
>      >  extern bool initcall_debug;
>      > +#else
>      > +static const bool initcall_debug = false;
>      > +#endif /* CONFIG_DEBUG_INITCALL */
>      >
>      >  #endif
>      >
>      > diff --git a/init/main.c b/init/main.c
>      > index ff49a6d..65837f7 100644
>      > --- a/init/main.c
>      > +++ b/init/main.c
>      > @@ -648,8 +648,10 @@ static void __init do_ctors(void)
>      >  #endif
>      >  }
>      >
>      > +#ifdef CONFIG_DEBUG_INITCALL
>      >  bool initcall_debug;
>      >  core_param(initcall_debug, initcall_debug, bool, 0644);
>      > +#endif /* CONFIG_DEBUG_INITCALL */
>      >
>      >  static char msgbuf[64];
>      >
>      > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>      > index 8745ac7..424ac93 100644
>      > --- a/lib/Kconfig.debug
>      > +++ b/lib/Kconfig.debug
>      > @@ -769,6 +769,15 @@ config DEBUG_WRITECOUNT
>      >
>      >         If unsure, say N.
>      >
>      > +config DEBUG_INITCALL
>      > +     bool "Debug initcalls as they are executed"
>      > +     depends on DEBUG_KERNEL
>      > +     help
>      > +       Enable this for tracing initcalls during startup. Useful
>     for working
>      > +       out where the kernel is dying during startup.
>      > +
>      > +       If unsure, say N
>      > +
>      >  config DEBUG_MEMORY_INIT
>      >       bool "Debug memory initialisation" if EXPERT
>      >       default !EXPERT
>      > --

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