lkml.org 
[lkml]   [2017]   [Jan]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch 4/5] PTP: add PTP_SYS_OFFSET emulation via cross timestamps infrastructure
On Tue, Jan 24, 2017 at 06:32:43AM +0100, Richard Cochran wrote:
> On Mon, Jan 23, 2017 at 09:06:20PM -0200, Marcelo Tosatti wrote:
> > Can you please describe what problem exists with this scheme?
>
> This new kernel code exists just because chrony doesn't implement the
> PRECISE ioctl. Instead of adding new "fake" modes, just teach chrony
> about the better method.

The latest development code of chrony now supports the PRECISE ioctl.

I did some tests with an e1000e NIC (i219) and it seemed the stability
was slightly worse than with the non-PRECISE ioctl, but there was a
400-500ns offset between the two, so it should be much more accurate
(we finally have something that avoids the asymmetry on the PCI-e
bus?). Configuring the refclock with a shorter dpoll should compensate
for the decrease in stability. In any case, there is a "nocrossts"
option to not use the PRECISE ioctl even if it's supported.

--
Miroslav Lichvar

\
 
 \ /
  Last update: 2017-01-24 09:17    [W:0.048 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site