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    SubjectRe: RFC: remove __read_mostly
    On Thu, Dec 13, 2007 at 11:29:08PM +0100, Andi Kleen wrote:
    > Adrian Bunk <bunk@kernel.org> writes:
    > >
    > > -rwxrwxr-x 1 bunk bunk 46607243 2007-12-13 19:50 vmlinux.old
    > > -rwxrwxr-x 1 bunk bunk 46598691 2007-12-13 21:55 vmlinux
    >
    > File sizes are useless -- check size output.

    text data bss dec hex filename
    29268488 3697961 5222400 38188849 246b731 vmlinux.old
    29268435 3685565 5228784 38192784 246c690 vmlinux

    > > It's not a surprise that the kernel can become bigger when __read_mostly
    > > gets used, especially in cases where __read_mostly prevents gcc
    > > optimizations.
    >
    > What optimizations do you think it prevents? I don't think it
    > should change the gcc generated code at all; the only difference
    > should be to the linker.

    What I have seen recently was a static variable marked __read_mostly
    being read-only with some CONFIG_DEBUG_FOO=n.

    With __read_mostly gcc feeled obliged to emit a variable.

    Without __read_mostly, gcc optimized the variable away.

    > -Andi

    cu
    Adrian

    --

    "Is there not promise of rain?" Ling Tan asked suddenly out
    of the darkness. There had been need of rain for many days.
    "Only a promise," Lao Er said.
    Pearl S. Buck - Dragon Seed



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