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    SubjectRe: f_ops flag to speed up compatible ioctls in linux kernel
    Date wrote:
    > On Wed, Sep 01, 2004 at 10:22:45AM +0300, Michael S. Tsirkin wrote:
    >>Currently, on the x86_64 architecture, its quite tricky to make
    >>a char device ioctl work for an x86 executables.
    >>In particular,
    >> 1. there is a requirement that ioctl number is unique -
    >> which is hard to guarantee especially for out of kernel modules
    > Too bad.
    >> 2. there's a performance huge overhead for each compat call - there's
    >> a hash lookup in a global hash inside a lock_kernel -
    >> and I think compat performance *is* important.
    >>Further, adding a command to the ioctl suddenly requires changing
    >>two places - registration code and ioctl itself.
    > So don't add them. Adding a new ioctl is *NOT* a step to be taken lightly -
    > we used to be far too accepting in that area and as somebody who'd waded
    > through the resulting dungpiles over the last months I can tell you that
    > result is utterly revolting.
    > Excuse me, but I have zero sympathy to people who complain about obstacles
    > to dumping more into the same piles - it should be hard.

    I don't think he was complaining so much as providing a rationale for
    the patch he offered which is intended to make things better. Seemed to
    me like a good context for the patch.

    -bill davidsen (
    "The secret to procrastination is to put things off until the
    last possible moment - but no longer" -me
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