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Date: Mon, 30 Dec 2002 14:01:48 +0100
To: linux-kernel@vger.kernel.org
Subject: Re: How much we can trust packet timestamping
Message-ID: <20021230130148.GB1591@pusa.informat.uv.es>
References: <20021230112838.GA928@pusa.informat.uv.es> <1041253743.13097.3.camel@irongate.swansea.linux.org.uk>
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On Mon, Dec 30, 2002 at 01:09:03PM +0000, Alan Cox wrote:
> On Mon, 2002-12-30 at 11:28, uaca@alumni.uv.es wrote:
> > Hi all
> > 
> > IMHO The problem is quite complicated because
> > 
> > + common hardware is not designed for real time:
> > 
> > 	- sends multiple PDUs within one interrupt, and can be delayed
> > 	- Host adapter bus & infraestructure is not designed to garantee latency
> >   	etc...
> 
> The packet can be timestamped by the hardware receiving as well as by
> the kernel netif_rx code. This is actually intentional and there is
> hardware that supports doing IRQ raise time sampling which the driver
> can then use to get very accurate data.

Thanks Alan

Anybody know about a Linux driver that supports doing IRQ raise time
sampling? any doc/pointer/suggestion would be greatly appreciated

Thanks in advance

	Ulisses
                Debian GNU/Linux: a dream come true
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