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    SubjectRe: [PATCH RESEND] sched: add missing group change to qfq_change_class
    From: Paolo Valente <>
    Date: Tue, 7 Aug 2012 19:27:25 +0200

    > [Resending again, as the text was corrupted by the email client]
    > To speed up operations, QFQ internally divides classes into
    > groups. Which group a class belongs to depends on the ratio between
    > the maximum packet length and the weight of the class. Unfortunately
    > the function qfq_change_class lacks the steps for changing the group
    > of a class when the ratio max_pkt_len/weight of the class changes.
    > For example, when the last of the following three commands is
    > executed, the group of class 1:1 is not correctly changed:
    > tc disc add dev XXX root handle 1: qfq
    > tc class add dev XXX parent 1: qfq classid 1:1 weight 1
    > tc class change dev XXX parent 1: classid 1:1 qfq weight 4
    > Not changing the group of a class does not affect the long-term
    > bandwidth guaranteed to the class, as the latter is independent of the
    > maximum packet length, and correctly changes (only) if the weight of
    > the class changes. In contrast, if the group of the class is not
    > updated, the class is still guaranteed the short-term bandwidth and
    > packet delay related to its old group, instead of the guarantees that
    > it should receive according to its new weight and/or maximum packet
    > length. This may also break service guarantees for other classes.
    > This patch adds the missing operations.
    > Signed-off-by: Paolo Valente <>

    Applied, thanks.

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