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Date: Tue, 14 Oct 2014 14:12:02 +0000 From: Thomas Shao <huishao@...rosoft.com> To: Richard Cochran <richardcochran@...il.com> CC: "tglx@...utronix.de" <tglx@...utronix.de>, "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>, "olaf@...fle.de" <olaf@...fle.de>, "apw@...onical.com" <apw@...onical.com>, "jasowang@...hat.com" <jasowang@...hat.com>, KY Srinivasan <kys@...rosoft.com> Subject: RE: [PATCH 2/2] hyperv: Implement Time Synchronization using host time sample > -----Original Message----- > From: Richard Cochran [mailto:richardcochran@...il.com] > Sent: Tuesday, October 14, 2014 9:26 PM > To: Thomas Shao > Cc: tglx@...utronix.de; gregkh@...uxfoundation.org; linux- > kernel@...r.kernel.org; devel@...uxdriverproject.org; olaf@...fle.de; > apw@...onical.com; jasowang@...hat.com; KY Srinivasan > Subject: Re: [PATCH 2/2] hyperv: Implement Time Synchronization using host > time sample > > On Tue, Oct 14, 2014 at 01:04:35PM +0000, Thomas Shao wrote: > > > I really don't see the need for this. We have NTP. If the guests > > > want to, they may use it. Otherwise, they have a free running clock, just > like real machines. > > > > > Sometimes the user can't setup NTP. For example the guest OS didn't > > have network connection. And in some cases, they may want the guest > time sync with host. > > With the existing hyper-v time source, the system clock will has > > around 1.5 second time drift per day. If the workload in the host is heavy, > the number could be larger. > > So this feature is really useful for some scenarios. > > Any real machine without networking (and without GPS etc) will drift. That is > just life, tough as it is. Why should we treat these guests any differently than > real machines? > > Furthermore, without networking you really don't have a compelling need > for correct absolute time in the first place. The host machine can be configure with NTP. And in this case, making guest time sync with host is useful. > > Thanks, > Richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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