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    SubjectRe: [PATCH] Time sliced CFQ #2
    On Mon, Dec 06, 2004 at 12:59:43PM +1100, Con Kolivas wrote:
    > Jeff Sipek wrote:
    > >I started working on the rudimentary io prio code, and it got me
    > >thinking...
    > >Why use the cpu scheduler priorities? Wouldn't it make more sense to add
    > >io_prio to task_struct? This way you can have a process which you know
    > >needs
    > >a lot of CPU but not as much io, or the other way around.
    >
    > That is the design the Jens' original ioprio code used which we used in
    > -ck for quite a while. What myself and -ck users found, though, was that
    > being tied to cpu 'nice' meant that most tasks behaved pretty much as
    > we'd expect based on one sys call.
    >
    > I think what is ideal is to have both.

    Agreed.

    > First the ioprio should be set to
    > what the cpu 'nice' level is as a sort of global "this is the priority
    > of this task" setting. Then it should also support changing of this
    > priority with a different call separate from the cpu nice. That way we
    > can take into account access privileges of the caller making it
    > impossible to set a high ioprio if the task itself is heavily niced by a
    > superuser and so on.

    This sounds very reasonable. How would a situation like this one get
    handeled:

    nice = x
    io_prio = y

    where x!=y

    then, user changes nice. Does the nice level change alone? If so,
    providing some "reset to nice==io_prio" capability would make sense, no?

    Jeff.
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