Hi Jacob! Thanks for replying.
I’ve had it set to 1ms without any problems. Only when booting some servers
through PXE boot (where the PTP slave is the PXE boot server) the PTP slave
server will be interrupted. I suspect this is due to heavy network load.
I have increased the tx_timestamp_timeout gradually up untill the PTP slave
instance was not interrupted anymore when booting several servers through PXE.
This was at the value of around 175ms. Therefore, I have set the value to 200ms
just to play it safe.
This was however only just a test environment in which four servers were PXE
booted at the same time. Now what will happen when in the production
environment for example 10 server will be booted at the same time? I would
probably have to manually increase the value again. This is not really an
option ofcourse as everything should be automated or work out of the box.
The driver in the PTP slave machine is the e1000e driver version 3.2.6k. I have
updated this to version 3.4.2 but then it wouldn’t even work anymore at all.
I don’t know for sure, but is it safe to assume this is due to heavy network
load or would the problem be somewhere else?
Could there be any possibility of prioritising PTP traffic at kernel level to
ensure the PTP packets will be timestamped within the default of 1ms (or at
least a value at which I can safely boot multiple other servers without
interruption).
Jord Pool
IT Service Management
________________________________
From: Keller, Jacob E <jacob.e.kel...@intel.com>
Sent: Friday, July 27, 2018 10:25:06 PM
To: Jord Pool; Richard Cochran; Cliff Spradlin via Linuxptp-users
Subject: RE: [Linuxptp-users] PXE Boot
> -----Original Message-----
> From: Jord Pool [mailto:jord.p...@outlook.com]
> Sent: Thursday, July 26, 2018 11:59 PM
> To: Richard Cochran <richardcoch...@gmail.com>; Cliff Spradlin via Linuxptp-
> users <linuxptp-users@lists.sourceforge.net>
> Subject: Re: [Linuxptp-users] PXE Boot
>
> Hi all!
>
> As I explained in my previous email, when PXE booting, the PXE boot server
> that
> runs in slave mode will have it’s PTP slave instance interrupted, unless I
> set the
> tx_timestamp_timeout to ~200ms. Now what happens when booting more than
> four server at the same time via PXE boot? Will I then have to increase the
> tx_timestamp_timeout value again? This is not really the most practical way of
> being able for the PXE boot server (PTP Slave) to keep synchronised.
>
> To solve the problem above, maybe there is a way to prioritise the PTP network
> traffic so that it will not have any interference with servers booting
> through PXE?
>
> Jord
>
Hi Jord,
The reason you need to increase the Tx timeout is that the driver you're using
is taking too long to report the timestamp. It's almost certainly either a
driver/hardware limitation, or a bug in the driver.
Basically, ptp4l is sending a Tx packet with a timestmap request, and waits up
to 1 millisecond for a response. But you increased this limit ot have it wait
200 milliseconds. This means that the driver is taking longer than 1
millisecond to send the packet, get the timestamp, and report it back... If it
fails when the timeout is 200 milliseconds, then it's taking over 1/5th of a
second to do this...
What driver/hardware are you using?
Thanks,
Jake
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