From: Thomas Shao <huishao@microsoft.com> To: Sitsofe Wheeler <sitsofe@gmail.com>, Olaf Hering <olaf@aepfle.de> Cc: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "driverdev-devel@linuxdriverproject.org" <driverdev-devel@linuxdriverproject.org>, "apw@canonical.com" <apw@canonical.com>, "jasowang@redhat.com" <jasowang@redhat.com>, "KY Srinivasan" <kys@microsoft.com>, Haiyang Zhang <haiyangz@microsoft.com> Subject: RE: [PATCH] Drivers: hv: util: Implement Time Synchronization using host time sample Date: Thu, 25 Sep 2014 09:40:42 +0000 [thread overview] Message-ID: <CD2CABCB2C0A0D4682C5F8AD84014154094643@HKXPRD3002MB006.064d.mgd.msft.net> (raw) In-Reply-To: <20140925060745.GA9450@sucs.org> > -----Original Message----- > From: Sitsofe Wheeler [mailto:sitsofe@gmail.com] > Sent: Thursday, September 25, 2014 2:08 PM > To: Olaf Hering > Cc: Thomas Shao; gregkh@linuxfoundation.org; linux- > kernel@vger.kernel.org; driverdev-devel@linuxdriverproject.org; > apw@canonical.com; jasowang@redhat.com; KY Srinivasan; Haiyang Zhang > Subject: Re: [PATCH] Drivers: hv: util: Implement Time Synchronization using > host time sample > > On Tue, Sep 23, 2014 at 09:56:10AM +0200, Olaf Hering wrote: > > On Tue, Sep 23, Thomas Shao wrote: > > > > > In current hyper-v time sync service,it only gets the initial clock > > > time from the host. It didn't process the following time samples. > > > This change introduced a module parameter called host_time_sync. If > > > it is set to true, the guest will periodically sychronize it's time > > > with the host clock using host time sample. By default it is > > > disabled, because we still recommend user to configure NTP for time > synchronization. > > You [Microsoft?] do? Can you link to public sources where is this stated > please? I don't see any mention of doing this on > http://technet.microsoft.com/en-us/library/dn720239.aspx .. The only > official Microsoft information with respect to Hyper-V guest time > synchronisation I've seen has been for Windows guests but perhaps I've > looked in the wrong places. > > The reason I ask is because regular ntpd is not enough to discipline a Linux > Hyper-V guest's clock. So much drift can occur under load that ntpd can't > bring the clock under sync. For now, I've been using Chrony which has a > higher tolerance for correcting drifting clocks. I'm not the only one seeing this > either (see http://serverfault.com/a/488528/203726 > and > http://serverfault.com/questions/523389/linux-clock-loses-10-minutes- > every-week > ). > > It would be good to something official about this issue as it is painful when > happens. > Hi Sitsofe, As far as I know, currently the document about time sync in Hyper-V is only for Windows. Below is a doc from MSDN: http://blogs.msdn.com/b/virtual_pc_guy/archive/2010/11/19/time-synchronization-in-hyper-v.aspx We are working on the document about Time Sync on Hyper-V to cover both Linux and Windows. > -- > Sitsofe | http://sucs.org/~sits/
WARNING: multiple messages have this Message-ID (diff)
From: Thomas Shao <huishao@microsoft.com> To: Sitsofe Wheeler <sitsofe@gmail.com>, Olaf Hering <olaf@aepfle.de> Cc: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>, "jasowang@redhat.com" <jasowang@redhat.com>, "driverdev-devel@linuxdriverproject.org" <driverdev-devel@linuxdriverproject.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "apw@canonical.com" <apw@canonical.com>, Haiyang Zhang <haiyangz@microsoft.com> Subject: RE: [PATCH] Drivers: hv: util: Implement Time Synchronization using host time sample Date: Thu, 25 Sep 2014 09:40:42 +0000 [thread overview] Message-ID: <CD2CABCB2C0A0D4682C5F8AD84014154094643@HKXPRD3002MB006.064d.mgd.msft.net> (raw) In-Reply-To: <20140925060745.GA9450@sucs.org> > -----Original Message----- > From: Sitsofe Wheeler [mailto:sitsofe@gmail.com] > Sent: Thursday, September 25, 2014 2:08 PM > To: Olaf Hering > Cc: Thomas Shao; gregkh@linuxfoundation.org; linux- > kernel@vger.kernel.org; driverdev-devel@linuxdriverproject.org; > apw@canonical.com; jasowang@redhat.com; KY Srinivasan; Haiyang Zhang > Subject: Re: [PATCH] Drivers: hv: util: Implement Time Synchronization using > host time sample > > On Tue, Sep 23, 2014 at 09:56:10AM +0200, Olaf Hering wrote: > > On Tue, Sep 23, Thomas Shao wrote: > > > > > In current hyper-v time sync service,it only gets the initial clock > > > time from the host. It didn't process the following time samples. > > > This change introduced a module parameter called host_time_sync. If > > > it is set to true, the guest will periodically sychronize it's time > > > with the host clock using host time sample. By default it is > > > disabled, because we still recommend user to configure NTP for time > synchronization. > > You [Microsoft?] do? Can you link to public sources where is this stated > please? I don't see any mention of doing this on > http://technet.microsoft.com/en-us/library/dn720239.aspx .. The only > official Microsoft information with respect to Hyper-V guest time > synchronisation I've seen has been for Windows guests but perhaps I've > looked in the wrong places. > > The reason I ask is because regular ntpd is not enough to discipline a Linux > Hyper-V guest's clock. So much drift can occur under load that ntpd can't > bring the clock under sync. For now, I've been using Chrony which has a > higher tolerance for correcting drifting clocks. I'm not the only one seeing this > either (see http://serverfault.com/a/488528/203726 > and > http://serverfault.com/questions/523389/linux-clock-loses-10-minutes- > every-week > ). > > It would be good to something official about this issue as it is painful when > happens. > Hi Sitsofe, As far as I know, currently the document about time sync in Hyper-V is only for Windows. Below is a doc from MSDN: http://blogs.msdn.com/b/virtual_pc_guy/archive/2010/11/19/time-synchronization-in-hyper-v.aspx We are working on the document about Time Sync on Hyper-V to cover both Linux and Windows. > -- > Sitsofe | http://sucs.org/~sits/ _______________________________________________ devel mailing list devel@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
next prev parent reply other threads:[~2014-09-25 9:55 UTC|newest] Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-09-23 5:44 [PATCH] Drivers: hv: util: Implement Time Synchronization using host time sample Thomas Shao 2014-09-23 7:56 ` Olaf Hering 2014-09-23 7:56 ` Olaf Hering 2014-09-23 9:47 ` Thomas Shao 2014-09-23 9:47 ` Thomas Shao 2014-09-25 6:07 ` Sitsofe Wheeler 2014-09-25 9:40 ` Thomas Shao [this message] 2014-09-25 9:40 ` Thomas Shao 2014-09-25 13:28 ` Time keeps on slipping... on Hyper-V Sitsofe Wheeler 2014-09-25 13:28 ` Sitsofe Wheeler 2014-09-26 6:57 ` Thomas Shao 2014-09-26 6:57 ` Thomas Shao 2014-09-26 9:24 ` Mike Surcouf 2014-09-26 9:24 ` Mike Surcouf 2014-09-26 9:46 ` Thomas Shao 2014-09-26 9:46 ` Thomas Shao 2014-09-26 10:02 [PATCH] Drivers: hv: util: Implement Time Synchronization using host time sample Thomas Shao 2014-09-26 11:53 ` Mike Surcouf 2014-09-26 11:53 ` Mike Surcouf 2014-09-26 12:30 ` Thomas Shao 2014-09-26 12:30 ` Thomas Shao 2014-09-26 13:07 ` Mike Surcouf 2014-09-26 13:07 ` Mike Surcouf 2014-09-26 13:52 ` Mike Surcouf 2014-09-26 13:52 ` Mike Surcouf 2014-09-26 15:13 ` Thomas Shao 2014-09-26 15:13 ` Thomas Shao
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