netdev - Re: [PATCH net v3] net: cbs: Fix software cbs to consider packet sending time

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Message-Id: <20200324.161515.1787662512822595061.davem@davemloft.net>
Date:   Tue, 24 Mar 2020 16:15:15 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     ye.zh-yuan@...ionext.com
Cc:     netdev@...r.kernel.org, okamoto.satoru@...ionext.com,
        kojima.masahisa@...ionext.com, vinicius.gomes@...el.com,
        kuba@...nel.org
Subject: Re: [PATCH net v3] net: cbs: Fix software cbs to consider packet
 sending time

From: Zh-yuan Ye <ye.zh-yuan@...ionext.com>
Date: Tue, 24 Mar 2020 17:28:25 +0900

> Currently the software CBS does not consider the packet sending time
> when depleting the credits. It caused the throughput to be
> Idleslope[kbps] * (Port transmit rate[kbps] / |Sendslope[kbps]|) where
> Idleslope * (Port transmit rate / (Idleslope + |Sendslope|)) = Idleslope
> is expected. In order to fix the issue above, this patch takes the time
> when the packet sending completes into account by moving the anchor time
> variable "last" ahead to the send completion time upon transmission and
> adding wait when the next dequeue request comes before the send
> completion time of the previous packet.
> 
> changelog:
> V2->V3:
>  - remove unnecessary whitespace cleanup
>  - add the checks if port_rate is 0 before division
> 
> V1->V2:
>  - combine variable "send_completed" into "last"
>  - add the comment for estimate of the packet sending
> 
> Fixes: 585d763af09c ("net/sched: Introduce Credit Based Shaper (CBS) qdisc")
> Signed-off-by: Zh-yuan Ye <ye.zh-yuan@...ionext.com>
> Reviewed-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>

Applied and queued up for -stable, thank you.