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authorPaolo Valente <paolo.valente@unimore.it>2012-08-07 11:27:25 +0400
committerDavid S. Miller <davem@davemloft.net>2012-08-09 03:02:05 +0400
commitbe72f63b4cd5d6778cf7eb0d0a86f18f96b51c0c (patch)
treeda43c1f094372eb1e9d1cb4d7dfa70e0ea9ba2bd /block/blk-throttle.c
parenta37e6e344910a43b9ebc2bbf29a029f5ea942598 (diff)
downloadlinux-be72f63b4cd5d6778cf7eb0d0a86f18f96b51c0c.tar.xz
sched: add missing group change to qfq_change_class
[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 <paolo.valente@unimore.it> Signed-off-by: David S. Miller <davem@davemloft.net>
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