Here''s a confusing issue for you, I have a bunch of machines running Xen 4.1. The time in the BIOS was wrong at machine power on, so logically, I set the time in Dom0 with NTP and synced it back to the hardware clock (just in case). I restart the VMs which came up before the time changed, so that they would get the correct time on startup (as has always worked in the past with Xen 3.x). The VMs do *not* come up with the initial clock set by the system clock in Dom0, they persist in using the time before it was set on the host system (plus however many seconds/minutes etc.) have passed, so the original clock time on Dom0 is ticking along somewhere even though every utility in the system seems to report the ''correct'' time as I have set by NTP. Any ideas? I''m at my wit''s end with it, I''ve tried different kernels (albeit with [almost] the same config), both jeremy-git-xen-next-2.6.32 and linux 3.1.0+ (latest from git). I''ve tried with different Xen version 4.1.0/4.1.1/4.1.2 and the problem exists in each of them. I know that I can run NTP in each VM, but I''d like the system time to be correct at boot up as it will make the timestamps in the logs very confusing when it jumps back an hour. -- *Niall Fleming BSc. (Hons)* Systems Administrator Webanywhere Limited Phone: 0800 862 0131 Ext: 203 Web: http://www.webanywhere.co.uk Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21 3BB Registered in England with company number 4881346 _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
First off... take a look at http://wiki.debian.org/Xen, look for the section on ''clocksource/0: Time went backwards'' Niall Fleming wrote:> Here''s a confusing issue for you, I have a bunch of machines running > Xen 4.1. > > The time in the BIOS was wrong at machine power on, so logically, I > set the time in > Dom0 with NTP and synced it back to the hardware clock (just in case). > I restart the > VMs which came up before the time changed, so that they would get the > correct time > on startup (as has always worked in the past with Xen 3.x). > > The VMs do *not* come up with the initial clock set by the system > clock in Dom0, they > persist in using the time before it was set on the host system (plus > however many > seconds/minutes etc.) have passed, so the original clock time on Dom0 > is ticking along > somewhere even though every utility in the system seems to report the > ''correct'' time > as I have set by NTP. > > Any ideas? I''m at my wit''s end with it, I''ve tried different kernels > (albeit with [almost] the same > config), both jeremy-git-xen-next-2.6.32 and linux 3.1.0+ (latest from > git). I''ve tried with different > Xen version 4.1.0/4.1.1/4.1.2 and the problem exists in each of them. > > I know that I can run NTP in each VM, but I''d like the system time to > be correct at boot up as it > will make the timestamps in the logs very confusing when it jumps back > an hour. > > -- > > *Niall Fleming BSc. (Hons)* > Systems Administrator > Webanywhere Limited > > Phone: 0800 862 0131 Ext: 203 > Web: http://www.webanywhere.co.uk > > Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21 3BB > Registered in England with company number 4881346 > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users-- In theory, there is no difference between theory and practice. In<fnord> practice, there is. .... Yogi Berra _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
As stated I have no issue with drift whilst running. It''s on DomU boot, the time is not the time that dom0 is set to if dom0 time was changed after boot. *Niall Fleming BSc. (Hons)* Systems Administrator Webanywhere Limited Phone: 0800 862 0131 Ext: 203 Web: http://www.webanywhere.co.uk Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21 3BB Registered in England with company number 4881346 On 02/11/2011 11:39, Miles Fidelman wrote:> First off... take a look at http://wiki.debian.org/Xen, look for the > section on ''clocksource/0: Time went backwards'' > > Niall Fleming wrote: >> Here''s a confusing issue for you, I have a bunch of machines running >> Xen 4.1. >> >> The time in the BIOS was wrong at machine power on, so logically, I >> set the time in >> Dom0 with NTP and synced it back to the hardware clock (just in >> case). I restart the >> VMs which came up before the time changed, so that they would get the >> correct time >> on startup (as has always worked in the past with Xen 3.x). >> >> The VMs do *not* come up with the initial clock set by the system >> clock in Dom0, they >> persist in using the time before it was set on the host system (plus >> however many >> seconds/minutes etc.) have passed, so the original clock time on Dom0 >> is ticking along >> somewhere even though every utility in the system seems to report the >> ''correct'' time >> as I have set by NTP. >> >> Any ideas? I''m at my wit''s end with it, I''ve tried different kernels >> (albeit with [almost] the same >> config), both jeremy-git-xen-next-2.6.32 and linux 3.1.0+ (latest >> from git). I''ve tried with different >> Xen version 4.1.0/4.1.1/4.1.2 and the problem exists in each of them. >> >> I know that I can run NTP in each VM, but I''d like the system time to >> be correct at boot up as it >> will make the timestamps in the logs very confusing when it jumps >> back an hour. >> >> -- >> >> *Niall Fleming BSc. (Hons)* >> Systems Administrator >> Webanywhere Limited >> >> Phone: 0800 862 0131 Ext: 203 >> Web: http://www.webanywhere.co.uk >> >> Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21 3BB >> Registered in England with company number 4881346 >> >> >> _______________________________________________ >> Xen-users mailing list >> Xen-users@lists.xensource.com >> http://lists.xensource.com/xen-users > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
I''ve tried messing around with clocksources in both dom0 and domUs yesterday afternoon, nothing seemed to make a difference, setting independent wallclock appears to be impossible in Xen 4.x, there is no /proc/sys/xen directory nor files within to set a value in. Whatever the clocksource, the domu should boot with the current time from dom0! Which it doesn''t, if you have changed the time in dom0, somewhere dom0 is maintaining another clock which seems to be set on boot, and cannot be altered by normal means. *Niall Fleming BSc. (Hons)* Systems Administrator Webanywhere Limited Phone: 0800 862 0131 Ext: 203 Web: http://www.webanywhere.co.uk Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21 3BB Registered in England with company number 4881346 On 02/11/2011 12:07, Miles Fidelman wrote:> I was suggesting that you look at it for information about the > parameters that effect > where DomUs get there time from, notably: > xen.independent_wallclock > clocksource=jiffies > > There seem to be a number of combinations of what can be set in both > Dom0 and DomU. > > I happen to set up all of my machines using the "workaround #1" > configuration, and all > works fine - but one thing I note vis-a-vis your comments is that the > hardware clock > is not accessible from within my VMs > > You might want to read the prose under "workaround #3" - and follow > the links - this > prose is particularly suggestive: > > "set independent_wallclock to 0 (all domains; VMs will follow dom0''s > clock)" > > you might, for example, want to check what independent_wallclock is > set to, and where it''s being set > > > Niall Fleming wrote: >> As stated I have no issue with drift whilst running. >> >> It''s on DomU boot, the time is not the time that dom0 is set to if >> dom0 time was changed after boot. >> >> *Niall Fleming BSc. (Hons)* >> Systems Administrator >> Webanywhere Limited >> >> Phone: 0800 862 0131 Ext: 203 >> Web: http://www.webanywhere.co.uk >> >> Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21 3BB >> Registered in England with company number 4881346 >> >> On 02/11/2011 11:39, Miles Fidelman wrote: >>> First off... take a look at http://wiki.debian.org/Xen, look for the >>> section on ''clocksource/0: Time went backwards'' >>> >>> Niall Fleming wrote: >>>> Here''s a confusing issue for you, I have a bunch of machines >>>> running Xen 4.1. >>>> >>>> The time in the BIOS was wrong at machine power on, so logically, I >>>> set the time in >>>> Dom0 with NTP and synced it back to the hardware clock (just in >>>> case). I restart the >>>> VMs which came up before the time changed, so that they would get >>>> the correct time >>>> on startup (as has always worked in the past with Xen 3.x). >>>> >>>> The VMs do *not* come up with the initial clock set by the system >>>> clock in Dom0, they >>>> persist in using the time before it was set on the host system >>>> (plus however many >>>> seconds/minutes etc.) have passed, so the original clock time on >>>> Dom0 is ticking along >>>> somewhere even though every utility in the system seems to report >>>> the ''correct'' time >>>> as I have set by NTP. >>>> >>>> Any ideas? I''m at my wit''s end with it, I''ve tried different >>>> kernels (albeit with [almost] the same >>>> config), both jeremy-git-xen-next-2.6.32 and linux 3.1.0+ (latest >>>> from git). I''ve tried with different >>>> Xen version 4.1.0/4.1.1/4.1.2 and the problem exists in each of them. >>>> >>>> I know that I can run NTP in each VM, but I''d like the system time >>>> to be correct at boot up as it >>>> will make the timestamps in the logs very confusing when it jumps >>>> back an hour. >>>> >>>> -- >>>> >>>> *Niall Fleming BSc. (Hons)* >>>> Systems Administrator >>>> Webanywhere Limited >>>> >>>> Phone: 0800 862 0131 Ext: 203 >>>> Web: http://www.webanywhere.co.uk >>>> >>>> Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21 3BB >>>> Registered in England with company number 4881346 >>>> >>>> >>>> _______________________________________________ >>>> Xen-users mailing list >>>> Xen-users@lists.xensource.com >>>> http://lists.xensource.com/xen-users >>> >>> > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Does the very short answer "the domU time is calculated from a counter that is based of the dom0 uptime measured in nanoseconds - unless the domU is using clocksource=jiffies" make it clearer? Actually I''m not sure I got it 100% right on a technical point of view now (tired, zzzzz), but the basic meaning is right: You might be seeing a corner case where nothing but a dom0 reboot would help. But I think you can also change the domU clock source at run-time, so that might be preferrable right now. My "datacenter" also didn''t set the system clocks to UTC after some maintenance. I resorted to a 2hour-downtime for the database boxes. Not great. Time for yet another nagios check ;) Florian _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
So there''s nothing to ''fix'' it really... I tried changing the clocksource to jiffies in the domu, but the problem''s already there before this point, as the machine starts with the wrong time! ;) Ack. *Niall Fleming BSc. (Hons)* Systems Administrator Webanywhere Limited Phone: 0800 862 0131 Ext: 203 Web: http://www.webanywhere.co.uk Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21 3BB Registered in England with company number 4881346 On 02/11/2011 23:16, Florian Heigl wrote:> Does the very short answer > "the domU time is calculated from a counter that is based of the dom0 > uptime measured in nanoseconds - unless the domU is using > clocksource=jiffies" make it clearer? > > Actually I''m not sure I got it 100% right on a technical point of view > now (tired, zzzzz), but the basic meaning is right: > You might be seeing a corner case where nothing but a dom0 reboot would help. > But I think you can also change the domU clock source at run-time, so > that might be preferrable right now. > > My "datacenter" also didn''t set the system clocks to UTC after some > maintenance. I resorted to a 2hour-downtime for the database boxes. > Not great. Time for yet another nagios check ;) > > Florian > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users