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

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Message-ID: <CY1PR0401MB153671C2B94D23793C78B2BE92700@CY1PR0401MB1536.namprd04.prod.outlook.com>
Date:   Thu, 5 Oct 2017 19:17:03 +0000
From:   Rodney Cummings <rodney.cummings@...com>
To:     David Miller <davem@...emloft.net>
CC:     "levipearson@...il.com" <levipearson@...il.com>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "vinicius.gomes@...el.com" <vinicius.gomes@...el.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "jhs@...atatu.com" <jhs@...atatu.com>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
        "andre.guedes@...el.com" <andre.guedes@...el.com>,
        "ivan.briano@...el.com" <ivan.briano@...el.com>,
        "jesus.sanchez-palencia@...el.com" <jesus.sanchez-palencia@...el.com>,
        "boon.leong.ong@...el.com" <boon.leong.ong@...el.com>,
        "richardcochran@...il.com" <richardcochran@...il.com>,
        "henrik@...tad.us" <henrik@...tad.us>
Subject: RE: [next-queue PATCH v4 3/4] net/sched: Introduce Credit Based
 Shaper (CBS) qdisc

No excuse. If the software cannot meet the standard's requirements, it is non-conformant,
which means it cannot be called a standard credit-based shaper.

But... I have no objection if someone wants to try software-only. I'm just saying that it
is a waste of time for me.

> -----Original Message-----
> From: David Miller [mailto:davem@...emloft.net]
> Sent: Thursday, October 5, 2017 2:05 PM
> To: Rodney Cummings <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.