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    SubjectRe: [PATCH] linux-2.5.43_vsyscall_A0
    From said:
    > What I suggested is an arch specific syscall to shutdown vsyscalls
    > enterely for the current task and its childs,

    Then I misunderstood.

    > the vsyscall will call
    > into the real syscall with sysenter, and you will be able to
    > revirtualize gettimeofday/time like you do on x86 with ptrace.

    And the task-specific fixmap entry would point to a page that makes the normal
    system call?

    > what do you mean that uml needs the vsyscalls more than the other
    > archs?

    Because its system calls are much slower than the host's. It would benefit
    more from vsyscalls.

    > I much prefer you to keep trapping the gettimeofday and time with
    > ptrace after shutting down the vsyscalls for the current task, it's so
    > much cleaner.

    And so much slower.

    > The overhead of ptrace cannot be your point, if that
    > overhead is a showstopper uml isn't an option in the first place.

    I don't plan on using ptrace forever. That overhead is going to shrink, and
    vsyscalls are one way to make it shrink.

    I intend to make UML perform by grabbing whatever improvements from wherever
    I can get them, and if I can't get vsyscalls because they're not virtualizable,
    then, from my point of view, their design is broken.


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