From: Ertman, DavidX M
Sent: Tuesday, September 03, 2013 1:51 PM
To: 'Naga Rajesh'
Subject: RE: [E1000-devel] Give priority to the (software) time stamping thread
in e1000e
I was not referring to a Hardware Network analyzer. The e1000e driver has
support for using the built in 1588 clock to "Hardware Time Stamp" packets as
they leave and enter the interface. For received packets, this eliminates the
lag that is produced by having to pass the packet up the stack before they
receive time stamps. For transmitted packets, it time stamps them as they are
leaving the interface so that there is no lag between time stamping and the
actual transmittal of the packet (TX timestamps are then looped back around to
the error port of the socket).
The thing to remember about 1588 hardware timestamps is that they are NOT part
of the transmitted packet (unless you specifically build a packet that contains
this info - e.g. the PTP's follow-up packet), but are part of the socket
control messages (ancillary data).
Take a look at the code for ptp4l (PTP for Linux), it is available on
sourceforge [http://linuxptp.sourceforge.net/], and you should be able to get a
fair idea on how they are used.
From: Naga Rajesh [mailto:[email protected]]
Sent: Tuesday, September 03, 2013 1:32 PM
To: Ertman, DavidX M
Subject: Re: [E1000-devel] Give priority to the (software) time stamping thread
in e1000e
Hi David,
Yeah I have already looked into Hardware network analyzers. But they are too
expensive (and we need more than one). So I was trying to somehow improve
the accuracy in software. I have already improved it by using RTLinux and
also by setting the Interrupt Throttle rate parameter. It is almost good
enough, but I am still trying to push it. Can you please elaborate a bit
more on your first comment.
Thank you.
On Tue, Sep 3, 2013 at 9:21 PM, Ertman, DavidX M
<[email protected]<mailto:[email protected]>> wrote:
Actually, the piece you might be interested in is specifically Hardware
Timestamping, which is used by PTP. PTP's primary purpose is to sync clocks on
a network, which might be of no interest to you.
Check out "ptp4l" for some sample code on how to use/access the 1588 clock.
-----Original Message-----
From: Ertman, DavidX M
[mailto:[email protected]<mailto:[email protected]>]
Sent: Tuesday, September 03, 2013 11:37 AM
To: Rajesh
Cc: [email protected]<mailto:[email protected]>
Subject: Re: [E1000-devel] Give priority to the (software) time stamping thread
in e1000e
Have you looked at PTP (IEEE 1588-2008), which uses the hardware clock to
timestamp packets as soon as they leave or enter the interface? If you are
looking for maximum accuracy this might be of interest to you.
-----Original Message-----
From: Rajesh [mailto:[email protected]<mailto:[email protected]>]
Sent: Friday, August 30, 2013 2:53 AM
To: [email protected]<mailto:[email protected]>
Subject: [E1000-devel] Give priority to the (software) time stamping thread in
e1000e
Hi,
I am new to linux programming. I have an intel NIC with e1000e driver. I am
working on precise time stamping of packets being captured from a network. An
interrupt is generated at every packet reception. Thus an interrupt handler
registered by the driver queues the captured packets and timestamps it.
My question is
If want to use RT Linux how can I increase the priority of the time stamping
thread.
Is this possible?
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--
Naga Rajesh Garikiparthi
Master of Science in Electrical and Computer Engineering
Technische Universität Kaiserslautern
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