Re: [PATCH 1/2] kbuild: Support split debug info v4

Michal Marek
2014-07-30T21:49:47Z

Dne 30.7.2014 20:50, Andi Kleen napsal(a):
> From: Andi Kleen <ak@linux.intel.com>
>
> This is an alternative approach to lower the overhead of debug info
> (as we discussed a few days ago)
>
> gcc 4.7+ and newer binutils have a new "split debug info" debug info
> model where the debug info is only written once into central ".dwo" files.
>
> This avoids having to copy it around multiple times, from the object
> files to the final executable. It lowers the disk space
> requirements. In addition it defaults to compressed debug data.
>
> More details here: http://gcc.gnu.org/wiki/DebugFission
>
> This patch adds a new option to enable it. It has to be an option,
> because it'll undoubtedly break everyone's debuginfo packaging scheme.
> gdb/objdump/etc. all still work, if you have new enough versions.
>
> I don't see big compile wins (maybe a second or two faster or so), but the
> object dirs with debuginfo get significantly smaller. My standard kernel
> config (slightly bigger than defconfig) shrinks from 2.9G disk space
> to 1.1G objdir (with non reduced debuginfo). I presume if you are IO limited
> the compile time difference will be larger.
>
> Only problem I've seen so far is that it doesn't play well with older
> versions of ccache (apparently fixed, see
> https://bugzilla.samba.org/show_bug.cgi?id=10005)
>
> v2: various fixes from Dirk Gouders. Improve commit message slightly.
> v3: Fix clean rules and improve Kconfig slightly
> v4: Fix merge error in last version (Sam Ravnborg)
> Clarify description that it mainly helps disk size.
> Cc: Dirk Gouders <dirk@gouders.net>
> Cc: mmarek@suse.cz
> Signed-off-by: Andi Kleen <ak@linux.intel.com>

I applied both patches to kbuild.git#kbuild.

Michal