netdev - Re: [PATCH] [RFC v3] packet: experimental support for 64-bit timestamps

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Message-ID: <CAF=yD-+UOPN+fJSHDp7ytiABM1aS1JD6Q-o-nvBc6d2Wzet6Qg@mail.gmail.com>
Date:   Wed, 29 Nov 2017 11:51:14 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Willem de Bruijn <willemb@...gle.com>,
        Björn Töpel <bjorn.topel@...il.com>,
        Richard Cochran <richardcochran@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mike Maloney <maloney@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Hans Liljestrand <ishkamiel@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        "Rosen, Rami" <rami.rosen@...el.com>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        Sowmini Varadhan <sowmini.varadhan@...cle.com>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [RFC v3] packet: experimental support for 64-bit timestamps

> Thanks for the review! Any suggestions for how to do the testing? If you have
> existing test cases, could you give my next version a test run to see if there
> are any regressions and if the timestamps work as expected?
>
> I see that there are test cases in tools/testing/selftests/net/, but none
> of them seem to use the time stamps so far, and I'm not overly familiar
> with how it works in the details to extend it in a meaningful way.

I could not find any good tests for this interface, either. The only
user of the interface I found was a little tool I wrote a few years
ago that compares timestamps at multiple points in the transmit
path for latency measurement [1]. But it may be easier to just write
a new test under tools/testing/selftests/net for this purpose. I can
help with that, too, if you want.

[1] https://github.com/wdebruij/kerneltools/blob/master/tools/tcplate/tcplate.c