netdev - Re: [next-queue PATCH v4 3/4] net/sched: Introduce Credit Based Shaper (CBS) qdisc

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Message-Id: <20171005.120508.2267452751875787466.davem@davemloft.net>
Date:   Thu, 05 Oct 2017 12:05:08 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     rodney.cummings@...com
Cc:     levipearson@...il.com, jiri@...nulli.us, vinicius.gomes@...el.com,
        netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org,
        jhs@...atatu.com, xiyou.wangcong@...il.com, andre.guedes@...el.com,
        ivan.briano@...el.com, jesus.sanchez-palencia@...el.com,
        boon.leong.ong@...el.com, richardcochran@...il.com,
        henrik@...tad.us
Subject: Re: [next-queue PATCH v4 3/4] net/sched: Introduce Credit Based
 Shaper (CBS) qdisc

From: Rodney Cummings <rodney.cummings@...com>
Date: Thu, 5 Oct 2017 18:41:48 +0000

> The IEEE Std 802.1Q specs for credit-based shaper require precise transmit decisions
> within a 125 microsecond window of time.
> 
> Even with the Preempt RT patch or similar enhancements, that isn't very practical
> as software-only. I doubt that software would conform to the standard's
> requirements.
> 
> This is analogous to memory, or CPU.

I feel like this is looking for an excuse to not have to at least try to implement
the software version of CBS.