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    From
    SubjectRe: [TRIVIAL] kstrdup
    Date
    Followup to:  <3EA0469D.7090602@pobox.com>
    By author: Jeff Garzik <jgarzik@pobox.com>
    In newsgroup: linux.dev.kernel
    >
    > That's kinda cute. Why not submit a patch to the strcpy implementation
    > in include/asm-i386/string.h? :) Ours is shorter, but does have a jump:
    > "1:\tlodsb\n\t"
    > "stosb\n\t"
    > "testb %%al,%%al\n\t"
    > "jne 1b"
    >
    > Which is better? I don't know; I'm still learning the performance
    > eccentricities of x86 insns on various processors.
    >

    It varies from porocessor to processor, and also depends on usage.

    >
    > Related x86 question: if the memory buffer is not dword-aligned, is
    > 'rep movsl' the best idea? On RISC it's usually smarter to unroll the
    > head of the loop to avoid unaligned accesses; but from reading x86 asm
    > code in the kernel, nobody seems to care about that. Is the
    > unaligned-access penalty so small that the increased code size of the
    > head-unroll is never worth it?
    >

    A lot of the newer x86 processors will perform this unrolling in
    microcode.

    -hpa
    --
    <hpa@transmeta.com> at work, <hpa@zytor.com> in private!
    "Unix gives you enough rope to shoot yourself in the foot."
    Architectures needed: ia64 m68k mips64 ppc ppc64 s390 s390x sh v850 x86-64
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