netdev - Re: [PATCH net-next 2/2] igb: offer a PTP Hardware Clock instead of the timecompare method

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Message-ID: <20111213044020.GA14322@netboy.at.omicron.at>
Date:	Tue, 13 Dec 2011 05:40:20 +0100
From:	Richard Cochran <richardcochran@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, e1000-devel@...ts.sourceforge.net,
	Jacob Keller <jacob.e.keller@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	John Ronciak <john.ronciak@...el.com>,
	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH net-next 2/2] igb: offer a PTP Hardware Clock instead
 of the timecompare method

On Tue, Dec 13, 2011 at 04:52:29AM +0100, Eric Dumazet wrote:
> > It is too bad that we have to take the spinlock for every time stamped
> > packet, but it is the hardware's fault for not providing a 64 bit wide
> > nanosecond time register.
> > 
> 
> Yes, probably. Are you sure a workaround is not possible, using a
> seqlock for synchronization of threads, and two hardware reads ?

Many things are possible...
 
> Or maybe it doesnt matter at all :)

Yes, I think it not worth the effort.  In general, the whole time
stamping thing is at odds with network throughput.

Richard
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