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    SubjectRe: [ABOMINATION] x86: Fast interrupt return to userspace

    * Andy Lutomirski <luto@amacapital.net> wrote:

    > > Whatever. I got enough profile data to say that it seems to have
    > > cut 'iret' overhead by at least two thirds. So it may not *work*,
    > > but from a "hey look, some random numbers" standpoint it is worth
    > > playing with.
    >
    > :)
    >
    > Is there actual interest in turning something like this into a real
    > patch? It would almost certainly have to default off and no one
    > sane would ever use it except for special-purpose machines.

    The macro speedup looks rather impressive, and we've done ugly things
    for far smaller speedups.

    But I don't think it should be a 'special mode'. It either is made to
    work unconditionally and can be a prime speedup to be proud of in a
    politely disgusted fashion, or we don't want the complexity (and
    future bitrot) of some special switch.

    At minimum it can be a "look we want this speedup in hardware"
    testcase to CPU designers.

    Thanks,

    Ingo


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