• Andi Kleen's avatar
    kbuild: Support split debug info v4 · 866ced95
    Andi Kleen authored
    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>
    Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
    Acked-by: default avatarSam Ravnborg <sam@ravnborg.org>
    Signed-off-by: default avatarMichal Marek <mmarek@suse.cz>
    866ced95
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