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    SubjectRe: [RFC][PATCH] TTY flip buffer SMP changes
    (Sorry not quoting but if you will use attachments 8))

    Problem 1:
    Agree. Using a common function is definitely needed, lets at least have
    all the bugs in one place.

    Problem 2:
    Known. See the comment in the Documentation/tty.txt

    Problem 3:
    The buffering model is useless for virtualised devices or high speeds.

    I've been pondering taking a very small performance hit to fix the
    entire flipping mess (pardon the pun) and also to speed up the actual
    common critical path (ppp) in the process.

    Now that networking is not a kernel option it seems slightly dumb that
    the tty layer doesn't just use the sk_buff model (probably not code).
    kmalloc is very fast and it kills TTY_DONT_FLIP because every buffer is
    owned by _one_ person at a time. (sk_buff's dont direclty fit too well
    because we push both error and bits per byte and don't last time I
    checked support recycling).

    Another nice effect is simplifying the ldisc and driver level locking.
    Drivers queue buffers, ldiscs eat buffers. If the driver queues a buffer
    and there is temporarily no ldisc it does not get lost.

    This also saves us memory - most tty's spend most of their time idle.


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