netdev - Re: Extending socket timestamping API for NTP

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Message-id: <6004E65D-EFD0-486B-9229-D004C20A2010@me.com>
Date:   Mon, 27 Mar 2017 12:21:13 -0700
From:   Denny Page <dennypage@...com>
To:     Richard Cochran <richardcochran@...il.com>
Cc:     Miroslav Lichvar <mlichvar@...hat.com>, netdev@...r.kernel.org,
        Jiri Benc <jbenc@...hat.com>,
        "Keller, Jacob E" <jacob.e.keller@...el.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: Extending socket timestamping API for NTP

[Resend in plain text for vger]

> On Mar 27, 2017, at 11:28, Richard Cochran <richardcochran@...il.com> wrote:
> 
> On Mon, Mar 27, 2017 at 09:25:03AM -0700, Denny Page wrote:
> 
>> I agree that the values in the igb driver are incorrect. They were
>> middle of the range values from the old tables. At least for 100Mb,
>> Intel seems to know that the original table was incorrect. I’ve done
>> extensive measurements of the i210 and i211 at both 100Mb and
>> 1Gb. The “external link partner” numbers Intel currently publishes
>> for the 100Mb appear accurate.
> 
> Well, after reading this, I am more convinced than ever that doing the
> correction in user space is the right way.  If the one and only vendor
> who publishes numbers can't even get them straight, how on earth will
> we ever get the drivers right?

I think that on average, the Vendor’s numbers are likely to be more accurate than anyone else’s. The concept that independent software implementations are going to somehow obtain and maintain better numbers is too much of a stretch.

FWIW, My testing indicates that the 100Mb numbers that Intel currently publishes are quite accurate. I don’t believe that Intel did the driver corrections btw, if memory serves these values were lifted from the Mac.

Denny