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    SubjectRe: f_ops flag to speed up compatible ioctls in linux kernel
    On Wed, Sep 01, 2004 at 10:22:45AM +0300, Michael S. Tsirkin wrote:
    > Hello!
    > 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.
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