[lkml]   [2005]   [Dec]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    Subject[patch 00/2] improve .text size on gcc 4.0 and newer compilers
    this patchset (for the 2.6.16 tree) consists of two patches:


    the purpose of these patches is to reduce the kernel's .text size, in
    particular if CONFIG_CC_OPTIMIZE_FOR_SIZE is specified. The effect of
    the patches on x86 is:

    text data bss dec hex filename
    3286166 869852 387260 4543278 45532e vmlinux-orig
    3194123 955168 387260 4536551 4538e7 vmlinux-inline
    3119495 884960 387748 4392203 43050b vmlinux-inline+units
    437271 77646 32192 547109 85925 vmlinux-tiny-orig
    452694 77646 32192 562532 89564 vmlinux-tiny-inline
    431891 77422 32128 541441 84301 vmlinux-tiny-inline+units

    i.e. a 5.3% .text reduction (!) with a larger .config, and a 1.2% .text
    reduction with a smaller .config.

    i've also done test-builds with CC_OPTIMIZE_FOR_SIZE disabled:

    text data bss dec hex filename
    4080998 870384 387260 5338642 517612 vmlinux-speed-orig
    4084421 872024 387260 5343705 5189d9 vmlinux-speed-inline
    4010957 834048 387748 5232753 4fd871 vmlinux-speed-inline+units

    so the more flexible inlining did not result in many changes [which is
    good, we want gcc to inline those in the optimized-for-speed case], but
    unit-at-a-time optimization resulted in smaller code - very likely
    meaning speed advantages as well.

    unit-at-a-time still increases the kernel stack footprint somewhat (by
    about 5% in the CC_OPTIMIZE_FOR_SIZE case), but not by the insane degree
    gcc3 used to, which prompted the original -fno-unit-at-a-time addition.

    so i think the combination of the two patches is a win both for small
    and for large systems. In fact the 5.3% .text reduction for embedded
    kernels is very significant.

    the patches are against -git, and were test-built and test-booted on
    x86, using gcc 4.0.2.

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-12-28 12:50    [W:0.022 / U:11.536 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site