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As it says in rfc8260#section-3.5 about the fair capacity scheduler:
A fair capacity distribution between the streams is used. This
scheduler considers the lengths of the messages of each stream and
schedules them in a specific way to maintain an equal capacity for
all streams. The details are implementation dependent. interleaving
user messages allows for a better realization of the fair capacity
usage.
This patch adds Fair Capacity Scheduler based on the foundations added
by commit 5bbbbe32a431 ("sctp: introduce stream scheduler foundations"):
A fc_list and a fc_length are added into struct sctp_stream_out_ext and
a fc_list is added into struct sctp_stream. In .enqueue, when there are
chunks enqueued into a stream, this stream will be linked into stream->
fc_list by its fc_list ordered by its fc_length. In .dequeue, it always
picks up the 1st skb from stream->fc_list. In .dequeue_done, fc_length
is increased by chunk's len and update its location in stream->fc_list
according to the its new fc_length.
Note that when the new fc_length overflows in .dequeue_done, instead of
resetting all fc_lengths to 0, we only reduced them by U32_MAX / 4 to
avoid a moment of imbalance in the scheduling, as Marcelo suggested.
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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