netdev - Re: [PATCH net-next 1/2] sctp: add fair capacity stream scheduler

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Message-ID: <ZAexQCrc/5rmE1iw@t14s.localdomain>
Date:   Tue, 7 Mar 2023 18:48:48 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
        davem@...emloft.net, kuba@...nel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Neil Horman <nhorman@...driver.com>
Subject: Re: [PATCH net-next 1/2] sctp: add fair capacity stream scheduler

On Tue, Mar 07, 2023 at 04:23:26PM -0500, Xin Long wrote:
> 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@...il.com>

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>