> -----Original Message----- > From: Mike Surcouf [mailto:mps.surcouf.lkml@xxxxxxxxx] > Sent: Friday, September 26, 2014 5:24 PM > To: Thomas Shao > Cc: Sitsofe Wheeler; Olaf Hering; gregkh@xxxxxxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; driverdev-devel@xxxxxxxxxxxxxxxxxxxxxx; > apw@xxxxxxxxxxxxx; jasowang@xxxxxxxxxx; 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 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
