** Tags added: kernel-da-key kernel-hyper-v xenial yakkety zesty
** Also affects: linux (Ubuntu Zesty)
Importance: Undecided
Status: Confirmed
** Also affects: linux (Ubuntu Yakkety)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Xenial)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Xenial)
Status: New => Triaged
** Changed in: linux (Ubuntu Yakkety)
Status: New => Triaged
** Changed in: linux (Ubuntu Zesty)
Status: Confirmed => Triaged
** Changed in: linux (Ubuntu Xenial)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu Yakkety)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu Zesty)
Importance: Undecided => Medium
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https://bugs.launchpad.net/bugs/1676635
Title:
[Hyper-V] Implement Hyper-V PTP Source
Status in linux package in Ubuntu:
Triaged
Status in linux source package in Xenial:
Triaged
Status in linux source package in Yakkety:
Triaged
Status in linux source package in Zesty:
Triaged
Bug description:
Please include the following upstream commit into lts-xenial, 16.04
HWE, Yakkity, and Zesty. This will improve the behavior of timesync on
Hyper-V hosts while simultaneously using network time sync protocols
like NTP.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/hv/hv_util.c?id=3716a49a81ba19dda7202633a68b28564ba95eb5
commit 3716a49a81ba19dda7202633a68b28564ba95eb5
Author: Vitaly Kuznetsov <vkuzn...@redhat.com>
Date: Sat Feb 4 09:57:14 2017 -0700
hv_utils: implement Hyper-V PTP source
With TimeSync version 4 protocol support we started updating system time
continuously through the whole lifetime of Hyper-V guests. Every 5 seconds
there is a time sample from the host which triggers do_settimeofday[64]().
While the time from the host is very accurate such adjustments may cause
issues:
- Time is jumping forward and backward, some applications may misbehave.
- In case an NTP server runs in parallel and uses something else for time
sync (network, PTP,...) system time will never converge.
- Systemd starts annoying you by printing "Time has been changed" every 5
seconds to the system log.
Instead of doing in-kernel time adjustments offload the work to an
NTP client by exposing TimeSync messages as a PTP device. Users may now
decide what they want to use as a source.
I tested the solution with chrony, the config was:
refclock PHC /dev/ptp0 poll 3 dpoll -2 offset 0
The result I'm seeing is accurate enough, the time delta between the guest
and the host is almost always within [-10us, +10us], the in-kernel
solution
was giving us comparable results.
I also tried implementing PPS device instead of PTP by using not currently
used Hyper-V synthetic timers (we use only one of four for clockevent) but
with PPS source only chrony wasn't able to give me the required accuracy,
the delta often more that 100us.
Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
Signed-off-by: K. Y. Srinivasan <k...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
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