From: Eric Dumazet <eric.dumazet@gmail.com>
To: Richard Cochran <richardcochran@gmail.com>
Cc: Ingo Kofler <ikofler@edu.uni-klu.ac.at>, netdev@vger.kernel.org
Subject: Re: Problems obtaining software TX timestamps
Date: Thu, 09 Sep 2010 16:02:38 +0200 [thread overview]
Message-ID: <1284040958.2589.178.camel@edumazet-laptop> (raw)
In-Reply-To: <20100909135716.GA8706@riccoc20.at.omicron.at>
Le jeudi 09 septembre 2010 à 15:57 +0200, Richard Cochran a écrit :
> On Thu, Sep 09, 2010 at 10:26:06AM +0200, Ingo Kofler wrote:
> > Thank you very much for this clarification. Are there any drawbacks
> > with this approach, e.g. performance issues? Honestly, I am just
> > wondering why driver developers do not add this single line if it's
> > that easy....
>
> Adding the line only tests one flag, so it is not a huge performance
> hit. This fix is very recent, that is why it has not been used in MAC
> drivers yet.
Should drivers call it at start_xmit() time, or at tx completion time ?
1) start_xmit() time : Earlier than real hardware xmit (with up to 1000
packets queued in TX ring, delay might be very large)
2) tx completion time : After real hardware xmit
(on tg3, ethtool -c gives : tx-usecs: 72 , tx-frames: 53, so we can
have a delay of 72 us before NIC acknowledges the frame xmit)
next prev parent reply other threads:[~2010-09-09 14:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-08 12:11 Problems obtaining software TX timestamps Ingo Kofler
2010-09-08 15:12 ` Eric Dumazet
2010-09-08 21:21 ` Ingo Kofler
2010-09-08 21:24 ` David Miller
2010-09-09 6:35 ` Richard Cochran
2010-09-09 8:26 ` Ingo Kofler
2010-09-09 13:57 ` Richard Cochran
2010-09-09 14:02 ` Eric Dumazet [this message]
2010-09-09 14:31 ` Loke, Chetan
2010-09-09 17:32 ` Richard Cochran
2010-09-09 18:58 ` Eric Dumazet
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