> -----Original Message-----
> From: Mike Surcouf [mailto:mps.surcouf.l...@gmail.com]
> Sent: Friday, September 26, 2014 5:24 PM
> To: Thomas Shao
> Cc: Sitsofe Wheeler; Olaf Hering; gre...@linuxfoundation.org; linux-
> ker...@vger.kernel.org; driverdev-de...@linuxdriverproject.org;
> a...@canonical.com; jasow...@redhat.com; KY Srinivasan; Haiyang Zhang
> Subject: Re: Time keeps on slipping... on Hyper-V
>
> > We still recommend user to configure NTP in the guest VM. With the new
> > time sync feature in this patch, you could have one more option to enable
> the guest-host sync, if the NTP didn't work in the environment.
> > For example the guest VM didn't have network connection.
>
> Microsoft used to use host time-samples in their older drivers but this was
> dropped (when I don't know).
> Now we must use NTP to correct hyperv_clocksource which suffers from the
> usual problems associated with virtual environment cpu loading.
>
> Host time-samples in conjunction with an effective clock stability algorithm
> with slews rather than steps should be the default.
> NTP is a workaround and should not be the primary solution.
>
> I have seen a lots of posts for RHEL CENTOS Linux that have a
> FAST.hyper_clocksource confirmed by myself on CENTOS 6.5 and 7.0 (also
> confirmed by Olaf on SLES).
>
> If this patch steps the clock once in a while without any form of slewing then
> it has the potential to break things as files and logs travel BACK in time.
>
> Apologies Thomas could you send me the patch via email as lkml.org does
> not have it in the archives.
>
Sure. I'll send the package again. It's strange that this patch didn't in the
archives. And in my patch, it will slew the time, if the time drift is less
than 1 s. It only steps the clock if the drift is larger than 1 s.
> Regards Mike
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