Re: [Linuxptp-users] linuxptp tx_timestamp_timeout

[Richard C. <ric...@gm...>]

On Fri, Nov 13, 2015 at 01:26:45PM +0100, frank wrote:
> Hi,
> 
> I have a question wrt. to configuring linuxptp, what are "good values"
> for  tx_timestamp_timeout?

The smaller, the better.
 
> It seems that linuxptp fails to work if the rootfs is mounted with nfs.
> I debugged this a bit and it seems that already light nfs traffic causes
> the issue.

Sounds like a driver issue.  (You didn't tell us anything about your HW.)
 
> Is this expected? Is increasing the  tx_timestamp_timeout ok or will
> this cause other issues?

Your kernel doesn't support SO_SELECT_ERR_QUEUE, and so increasing the
timeout will mean that ptp4l will wait the full timeout duration, even
if the time stamp arrives earlier.  This happens on every transmitted
PTP event message (ie every Delay_Req when in the slave role).

> Currently the value is still the default:
> 
> tx_timestamp_timeout    1

That means one millisecond.  Try ten, and if that doesn't work, then
you likely have a driver/stack issue.

> $ sudo /usr/sbin/ptp4l -f /etc/linuxptp/ptp4l.conf -i eth0 -l6 -m
> ptp4l[1641.641]: selected /dev/ptp0 as PTP clock
> ptp4l[1641.677]: eth0: SO_SELECT_ERR_QUEUE: Protocol not available

If you upgrade your kernel, then you can set a longer timeout without
having to block the full duration on every message.

Thanks,
Richard