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    SubjectRe: [PATCH NET-NEXT 02/10] time sync: generic infrastructure to map between time stamps generated by a time counter and system time
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    On Mon, 2009-02-09 at 21:27 +0200, John Stultz wrote:
    > On Mon, 2009-02-09 at 18:02 +0100, Patrick Ohly wrote:
    > > Is this revision of the patch okay? How should the two patches get
    > > included in the main kernel - via netdev-next-2.6?
    >
    > Small comment below, but otherwise it looks ok to me. I usually push
    > patches through Andrew, so I'd probably go that way. But I'd leave it to
    > Dave if he's comfortable pushing them to Linus.

    As you don't mind, I suggest to push through Dave as part of the
    complete patch series. That way we don't need to worry about
    coordinating two subtrees.

    > Acked-by: John Stultz <johnstul@us.ibm.com>

    Thanks! Will add that.

    > > + /* ignore negative durations */
    > > + sample.duration_target = ktime_to_ns(ktime_sub(end, start));
    > > + if (sample.duration_target >= 0) {
    >
    > You may also want to checking the bounds on the duration_target. If
    > preemption hits and the values are too out of whack, the symetric delay
    > assumption below might be quite invalid.
    >
    > I guess the outliers removal probably covers this as well, but seems
    > some sanity checking might be good.

    That would require more information, like "duration_target is usually in
    the xxx-yyy range". This could be determined based on past measurements
    or the median of the current sample set, but is this really better than
    the current "remove longest 25%"?

    In practice I haven't seen such a problem, therefore I'd prefer to keep
    the code simple and not change it. It was tested under load conditions
    (both CPU and network).

    --
    Bye, Patrick Ohly
    --
    Patrick.Ohly@gmx.de
    http://www.estamos.de/




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