* Re: [Xen-users] Xen timekeeping best practices [not found] ` <alpine.DEB.2.00.1204131825410.16529@legendary.xserve.fr> @ 2012-04-13 17:22 ` Todd Deshane 2012-04-16 9:57 ` Ian Campbell 0 siblings, 1 reply; 8+ messages in thread From: Todd Deshane @ 2012-04-13 17:22 UTC (permalink / raw) To: Remi Gacogne; +Cc: Lloyd Dizon, xen-users, xen-devel mailing list Adding Xen-devel. What are the current timekeeping best practices now? Thanks, Todd ---------- Forwarded message ---------- From: Remi Gacogne <rgacogne-xen@valombre.net> Date: Fri, Apr 13, 2012 at 12:31 PM Subject: Re: [Xen-users] Xen timekeeping best practices To: Todd Deshane <todd.deshane@xen.org> Cc: Lloyd Dizon <thecarrionkind@gmail.com>, xen-users@lists.xen.org > Does this help at all: > http://wiki.xensource.com/wiki/Xen_FAQ_DomU#How_can_i_synchronize_a_dom0_clock.3F Well, thank you but independent_wallclock doesn't exist anymore on pvops kernel, and the link to blogspot seems broken so, no, not very much :) -- Regards, Remi Gacogne -- Todd Deshane http://www.linkedin.com/in/deshantm http://blog.xen.org/ http://wiki.xen.org/ ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [Xen-users] Xen timekeeping best practices 2012-04-13 17:22 ` [Xen-users] Xen timekeeping best practices Todd Deshane @ 2012-04-16 9:57 ` Ian Campbell 2012-04-16 12:55 ` [Xen-devel] " Remi Gacogne 2012-04-16 14:45 ` Lloyd Dizon 0 siblings, 2 replies; 8+ messages in thread From: Ian Campbell @ 2012-04-16 9:57 UTC (permalink / raw) To: Todd Deshane Cc: Lloyd Dizon, xen-users@lists.xen.org, xen-devel mailing list, Remi Gacogne On Fri, 2012-04-13 at 18:22 +0100, Todd Deshane wrote: > Adding Xen-devel. > > What are the current timekeeping best practices now? pvops kernels behave as if independent_wallclock == 1, so the existing advice: set /proc/sys/xen/independent_wallclock to 1 and run ntp on domU. still applies. Ian. > > Thanks, > Todd > > ---------- Forwarded message ---------- > From: Remi Gacogne <rgacogne-xen@valombre.net> > Date: Fri, Apr 13, 2012 at 12:31 PM > Subject: Re: [Xen-users] Xen timekeeping best practices > To: Todd Deshane <todd.deshane@xen.org> > Cc: Lloyd Dizon <thecarrionkind@gmail.com>, xen-users@lists.xen.org > > > > > Does this help at all: > > http://wiki.xensource.com/wiki/Xen_FAQ_DomU#How_can_i_synchronize_a_dom0_clock.3F > > > Well, thank you but independent_wallclock doesn't exist anymore on > pvops kernel, and the link to blogspot seems broken so, no, not very > much :) > > -- > > Regards, > > Remi Gacogne > > > ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [Xen-devel] Xen timekeeping best practices 2012-04-16 9:57 ` Ian Campbell @ 2012-04-16 12:55 ` Remi Gacogne 2012-04-16 14:45 ` Lloyd Dizon 1 sibling, 0 replies; 8+ messages in thread From: Remi Gacogne @ 2012-04-16 12:55 UTC (permalink / raw) To: Ian Campbell Cc: Lloyd Dizon, xen-users@lists.xen.org, Todd Deshane, xen-devel mailing list Hi Ian, >> What are the current timekeeping best practices now? > > pvops kernels behave as if independent_wallclock == 1, so the existing > advice: > set /proc/sys/xen/independent_wallclock to 1 and run ntp on > domU. > still applies. O, thanks! The thing is, we have several servers in Xen 4.0.1 using NTP in dom0 and domU. We didn't have any problem keeping a correct time with Xen 3 on the same servers, but with Xen 4 we have a recurring problem where the clock goes out of sync for an hour or so, in dom0 and domU at the same time. We have done more tests since friday, and it seems that this issue does not occur on servers having a Intel Xeon L5630, but on older servers having E5405 or L5410 processors. Looking at the output from xm dmesg, olders servers have : (XEN) checking TSC synchronization across 8 CPUs: passed. (XEN) Platform timer appears to have unexpectedly wrapped 10 or more times. (XEN) Platform timer is 3.579MHz ACPI PM Timer (XEN) CPUIDLE: disabled due to no HPET. Force enable with 'cpuidle'. where newer have : (XEN) TSC is reliable, synchronization unnecessary (XEN) Platform timer is 14.318MHz HPET I'm wondering if my issue could simply be linked to the fact that HPET is not available ? On newer servers, the ouput of # xm debug-key s; xm dmesg | tail is : (XEN) TSC marked as reliable, warp = 0 (count=4) (XEN) dom3: mode=0,ofs=0x42f57c62a36,khz=2133464,inc=1 (XEN) dom4: mode=0,ofs=0x430b996b94f,khz=2133464,inc=1 (XEN) dom5(hvm): mode=0,ofs=0x470ba656d26,khz=2133464,inc=1 (XEN) dom10(hvm): mode=0,ofs=0x6baa148c81f66,khz=2133464,inc=1 (XEN) No domains have emulated TSC whereas it is on olders servers : (XEN) Platform timer appears to have unexpectedly wrapped 10 or more times (XEN) TSC has constant rate, deep Cstates possible, so not reliable, warp=2310 (count=8) (XEN) dom1: mode=0,ofs=0x4379529ffa3,khz=2000068,inc=1,vtsc count: 5579056116 kernel, 18906545 user (XEN) dom2: mode=0,ofs=0x43a55ddb79e,khz=2000068,inc=1,vtsc count: 12684066480 kernel, 25277162 user (XEN) dom3: mode=0,ofs=0x43bd882b29e,khz=2000068,inc=1,vtsc count: 35568040315 kernel, 27356321 user Any idea would be appreciated ! Thanks, ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [Xen-devel] Xen timekeeping best practices 2012-04-16 9:57 ` Ian Campbell 2012-04-16 12:55 ` [Xen-devel] " Remi Gacogne @ 2012-04-16 14:45 ` Lloyd Dizon 2012-04-16 14:57 ` [Xen-users] " Ian Campbell 1 sibling, 1 reply; 8+ messages in thread From: Lloyd Dizon @ 2012-04-16 14:45 UTC (permalink / raw) To: Ian Campbell Cc: xen-users@lists.xen.org, Todd Deshane, xen-devel mailing list, Remi Gacogne On Mon, Apr 16, 2012 at 11:57 AM, Ian Campbell <Ian.Campbell@citrix.com> wrote: > > On Fri, 2012-04-13 at 18:22 +0100, Todd Deshane wrote: > > Adding Xen-devel. > > > > What are the current timekeeping best practices now? > > pvops kernels behave as if independent_wallclock == 1, so the existing > advice: > set /proc/sys/xen/independent_wallclock to 1 and run ntp on > domU. > still applies. This also applies to Xen 4.0 (4.0.0) if I understood correctly? If so and based on previous posts can we resume that this is what is recommended: | Xen3 | Xen4 | --------------------------------------------------------------------- PV | independent_wallclock = 0 or 1 | independent_wallclock = 1 | --------------------------------------------------------------------- HVM | independent_wallclock = 0 | independent_wallclock = 1 | --------------------------------------------------------------------- With priority to independent_wallclock=1 and if activated, ntp required. ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [Xen-users] Xen timekeeping best practices 2012-04-16 14:45 ` Lloyd Dizon @ 2012-04-16 14:57 ` Ian Campbell 2012-04-17 7:41 ` [Xen-devel] " Lloyd Dizon 0 siblings, 1 reply; 8+ messages in thread From: Ian Campbell @ 2012-04-16 14:57 UTC (permalink / raw) To: Lloyd Dizon Cc: xen-users@lists.xen.org, Todd Deshane, xen-devel mailing list, Remi Gacogne On Mon, 2012-04-16 at 15:45 +0100, Lloyd Dizon wrote: > On Mon, Apr 16, 2012 at 11:57 AM, Ian Campbell <Ian.Campbell@citrix.com> wrote: > > > > On Fri, 2012-04-13 at 18:22 +0100, Todd Deshane wrote: > > > Adding Xen-devel. > > > > > > What are the current timekeeping best practices now? > > > > pvops kernels behave as if independent_wallclock == 1, so the existing > > advice: > > set /proc/sys/xen/independent_wallclock to 1 and run ntp on > > domU. > > still applies. > > This also applies to Xen 4.0 (4.0.0) if I understood correctly? This is entirely a function of the guest kernel version and not the hypervisor > If so and based on previous posts can we resume that this is what is > recommended: If you s/Xen3/Classic XenoLinux Kernels/ and s/Xen4/Paravirt Ops Linux Kernels/g then I think it is somewhat accurate, at least for the PV line. I must confess I don't really know for the HVM line. I suspect that it is actually: Classic XenoLinux -- no PV time source, independent_wallclock means nothing, run NTP in the guest Paravirt ops kernels _without_ PV time PVHVM extensions -- no PV time source, independent_wallclock means nothing, run NTP in the guest Paravirt ops kernels _with_ PV time PVHVM extensions -- PV time source, independent_wallclock always == 1, run NTP. So in short always run NTP in an HVM guest, regardless of the presence or absence of PV time extensions. > | Xen3 | Xen4 | > --------------------------------------------------------------------- > PV | independent_wallclock = 0 or 1 | independent_wallclock = 1 | > --------------------------------------------------------------------- > HVM | independent_wallclock = 0 | independent_wallclock = 1 | > --------------------------------------------------------------------- > > With priority to independent_wallclock=1 and if activated, ntp required. ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [Xen-devel] Xen timekeeping best practices 2012-04-16 14:57 ` [Xen-users] " Ian Campbell @ 2012-04-17 7:41 ` Lloyd Dizon 2012-04-17 8:16 ` [Xen-users] " Ian Campbell 0 siblings, 1 reply; 8+ messages in thread From: Lloyd Dizon @ 2012-04-17 7:41 UTC (permalink / raw) To: Ian Campbell Cc: xen-users@lists.xen.org, Todd Deshane, xen-devel mailing list, Remi Gacogne On Mon, Apr 16, 2012 at 4:57 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote: > On Mon, 2012-04-16 at 15:45 +0100, Lloyd Dizon wrote: >> On Mon, Apr 16, 2012 at 11:57 AM, Ian Campbell <Ian.Campbell@citrix.com> wrote: >> > >> > On Fri, 2012-04-13 at 18:22 +0100, Todd Deshane wrote: >> > > Adding Xen-devel. >> > > >> > > What are the current timekeeping best practices now? >> > >> > pvops kernels behave as if independent_wallclock == 1, so the existing >> > advice: >> > set /proc/sys/xen/independent_wallclock to 1 and run ntp on >> > domU. >> > still applies. >> >> This also applies to Xen 4.0 (4.0.0) if I understood correctly? > > This is entirely a function of the guest kernel version and not the > hypervisor > >> If so and based on previous posts can we resume that this is what is >> recommended: > > If you s/Xen3/Classic XenoLinux Kernels/ and s/Xen4/Paravirt Ops Linux > Kernels/g then I think it is somewhat accurate, at least for the PV > line. > > I must confess I don't really know for the HVM line. I suspect that it > is actually: > > Classic XenoLinux -- no PV time source, independent_wallclock means > nothing, run NTP in the guest > > Paravirt ops kernels _without_ PV time PVHVM extensions -- no PV time > source, independent_wallclock means nothing, run NTP in the guest > > Paravirt ops kernels _with_ PV time PVHVM extensions -- PV time source, > independent_wallclock always == 1, run NTP. > > So in short always run NTP in an HVM guest, regardless of the presence > or absence of PV time extensions I do not fully understand the difference yet between and Classic XenoLinux and Paravirt Ops Kernel (will dig the info later) but here is the resume: ------------------------------------------------------------------------------------------------------------------- | Xen3: Classic XenoLinux Kern | Xen4: Paravirt Ops Linux Kern | -------------------------------------------------------------------------------------------------------------------------- PV | independent_wallclock = 0 or 1 | independent_wallclock = 1 | -------------------------------------------------------------------------------------------------------------------------- HVM | -> no PV timesource, no ind. wallclock, run NTP | -> w/o PV time PVHVM extensions, no ind. wallclock, run NTP | | | -> PV time source, ind. wallclock always 1, run NTP | -------------------------------------------------------------------------------------------------------------------------- Should we put this somewhere (wiki) until somebody else proves this is inaccurate ? ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [Xen-users] Xen timekeeping best practices 2012-04-17 7:41 ` [Xen-devel] " Lloyd Dizon @ 2012-04-17 8:16 ` Ian Campbell 2012-04-17 9:35 ` [Xen-devel] " Lloyd Dizon 0 siblings, 1 reply; 8+ messages in thread From: Ian Campbell @ 2012-04-17 8:16 UTC (permalink / raw) To: Lloyd Dizon Cc: xen-users@lists.xen.org, Todd Deshane, xen-devel mailing list, Remi Gacogne On Tue, 2012-04-17 at 08:41 +0100, Lloyd Dizon wrote: > On Mon, Apr 16, 2012 at 4:57 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote: > > On Mon, 2012-04-16 at 15:45 +0100, Lloyd Dizon wrote: > >> On Mon, Apr 16, 2012 at 11:57 AM, Ian Campbell <Ian.Campbell@citrix.com> wrote: > >> > > >> > On Fri, 2012-04-13 at 18:22 +0100, Todd Deshane wrote: > >> > > Adding Xen-devel. > >> > > > >> > > What are the current timekeeping best practices now? > >> > > >> > pvops kernels behave as if independent_wallclock == 1, so the existing > >> > advice: > >> > set /proc/sys/xen/independent_wallclock to 1 and run ntp on > >> > domU. > >> > still applies. > >> > >> This also applies to Xen 4.0 (4.0.0) if I understood correctly? > > > > This is entirely a function of the guest kernel version and not the > > hypervisor > > > >> If so and based on previous posts can we resume that this is what is > >> recommended: > > > > If you s/Xen3/Classic XenoLinux Kernels/ and s/Xen4/Paravirt Ops Linux > > Kernels/g then I think it is somewhat accurate, at least for the PV > > line. > > > > I must confess I don't really know for the HVM line. I suspect that it > > is actually: > > > > Classic XenoLinux -- no PV time source, independent_wallclock means > > nothing, run NTP in the guest > > > > Paravirt ops kernels _without_ PV time PVHVM extensions -- no PV time > > source, independent_wallclock means nothing, run NTP in the guest > > > > Paravirt ops kernels _with_ PV time PVHVM extensions -- PV time source, > > independent_wallclock always == 1, run NTP. > > > > So in short always run NTP in an HVM guest, regardless of the presence > > or absence of PV time extensions > > I do not fully understand the difference yet between and Classic > XenoLinux and Paravirt Ops Kernel (will dig the info later) Roughly: classic == old out-of-tree Xen patches, static compile time support for Xen. This is the old "2.6.18-xen.hg" tree and includes the "SuSE forward port kernels" which are the classic patches kept up to date with recent kernels. pvops == patches in upstream Linux, dynamic support for Xen enabled at kernel boot time. pvops supported domU from ~2.6.24 and dom0 from 3.0 onwards. > but here > is the resume: > > ------------------------------------------------------------------------------------------------------------------- > | Xen3: Classic XenoLinux Kern | > Xen4: Paravirt Ops Linux Kern | > -------------------------------------------------------------------------------------------------------------------------- > PV | independent_wallclock = 0 or 1 | > independent_wallclock = 1 | > -------------------------------------------------------------------------------------------------------------------------- > HVM | -> no PV timesource, no ind. wallclock, run NTP | -> w/o PV > time PVHVM extensions, no ind. wallclock, run NTP | > | | -> PV > time source, ind. wallclock always 1, run NTP | > -------------------------------------------------------------------------------------------------------------------------- It got a bit mangled in transit but it looks reasonable. You should remove "Xen3" and "Xen4" from the titles since the hypervisor version has no bearing on any of this. You can just as easily run a pvops kernel on Xen3.x or a classic kernel on Xen4.x (and of course you can mix and match those on a single host) The 3->4 major number transition was mostly just a version number bump, it didn't indicate any major change in the API or anything like that -- any PV kernel should run on any Xen from 3.0 onwards, right through to 4.2 (and beyond). > Should we put this somewhere (wiki) until somebody else proves this is > inaccurate ? Please do put it on the wiki, I think there was a reference to a page (a FAQ?) further up thread which seems like as good a place as any to add it. Ian. ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [Xen-devel] Xen timekeeping best practices 2012-04-17 8:16 ` [Xen-users] " Ian Campbell @ 2012-04-17 9:35 ` Lloyd Dizon 0 siblings, 0 replies; 8+ messages in thread From: Lloyd Dizon @ 2012-04-17 9:35 UTC (permalink / raw) To: Ian Campbell Cc: xen-users@lists.xen.org, Todd Deshane, xen-devel mailing list, Remi Gacogne On Tue, Apr 17, 2012 at 10:16 AM, Ian Campbell <Ian.Campbell@citrix.com> wrote: > On Tue, 2012-04-17 at 08:41 +0100, Lloyd Dizon wrote: >> On Mon, Apr 16, 2012 at 4:57 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote: >> > On Mon, 2012-04-16 at 15:45 +0100, Lloyd Dizon wrote: >> >> On Mon, Apr 16, 2012 at 11:57 AM, Ian Campbell <Ian.Campbell@citrix.com> wrote: >> >> > >> >> > On Fri, 2012-04-13 at 18:22 +0100, Todd Deshane wrote: >> >> > > Adding Xen-devel. >> >> > > >> >> > > What are the current timekeeping best practices now? >> >> > >> >> > pvops kernels behave as if independent_wallclock == 1, so the existing >> >> > advice: >> >> > set /proc/sys/xen/independent_wallclock to 1 and run ntp on >> >> > domU. >> >> > still applies. >> >> >> >> This also applies to Xen 4.0 (4.0.0) if I understood correctly? >> > >> > This is entirely a function of the guest kernel version and not the >> > hypervisor >> > >> >> If so and based on previous posts can we resume that this is what is >> >> recommended: >> > >> > If you s/Xen3/Classic XenoLinux Kernels/ and s/Xen4/Paravirt Ops Linux >> > Kernels/g then I think it is somewhat accurate, at least for the PV >> > line. >> > >> > I must confess I don't really know for the HVM line. I suspect that it >> > is actually: >> > >> > Classic XenoLinux -- no PV time source, independent_wallclock means >> > nothing, run NTP in the guest >> > >> > Paravirt ops kernels _without_ PV time PVHVM extensions -- no PV time >> > source, independent_wallclock means nothing, run NTP in the guest >> > >> > Paravirt ops kernels _with_ PV time PVHVM extensions -- PV time source, >> > independent_wallclock always == 1, run NTP. >> > >> > So in short always run NTP in an HVM guest, regardless of the presence >> > or absence of PV time extensions >> >> I do not fully understand the difference yet between and Classic >> XenoLinux and Paravirt Ops Kernel (will dig the info later) > > Roughly: > > classic == old out-of-tree Xen patches, static compile time support for > Xen. This is the old "2.6.18-xen.hg" tree and includes the "SuSE forward > port kernels" which are the classic patches kept up to date with recent > kernels. > > pvops == patches in upstream Linux, dynamic support for Xen enabled at > kernel boot time. pvops supported domU from ~2.6.24 and dom0 from 3.0 > onwards. Thanks also found info here: http://wiki.xensource.com/xenwiki/XenDom0Kernels.html >> but here >> is the resume: >> >> ------------------------------------------------------------------------------------------------------------------- >> | Xen3: Classic XenoLinux Kern | >> Xen4: Paravirt Ops Linux Kern | >> -------------------------------------------------------------------------------------------------------------------------- >> PV | independent_wallclock = 0 or 1 | >> independent_wallclock = 1 | >> -------------------------------------------------------------------------------------------------------------------------- >> HVM | -> no PV timesource, no ind. wallclock, run NTP | -> w/o PV >> time PVHVM extensions, no ind. wallclock, run NTP | >> | | -> PV >> time source, ind. wallclock always 1, run NTP | >> -------------------------------------------------------------------------------------------------------------------------- > > It got a bit mangled in transit but it looks reasonable. > > You should remove "Xen3" and "Xen4" from the titles since the hypervisor > version has no bearing on any of this. You can just as easily run a > pvops kernel on Xen3.x or a classic kernel on Xen4.x (and of course you > can mix and match those on a single host) > > The 3->4 major number transition was mostly just a version number bump, > it didn't indicate any major change in the API or anything like that -- > any PV kernel should run on any Xen from 3.0 onwards, right through to > 4.2 (and beyond). > >> Should we put this somewhere (wiki) until somebody else proves this is >> inaccurate ? > > Please do put it on the wiki, I think there was a reference to a page (a > FAQ?) further up thread which seems like as good a place as any to add > it. Done. Anybody please correct the information if inaccurate. http://wiki.xensource.com/wiki/Xen_FAQ_DomU#How_can_i_synchronize_a_dom0_clock.3F ^ permalink raw reply [flat|nested] 8+ messages in thread
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2012-04-13 17:22 ` [Xen-users] Xen timekeeping best practices Todd Deshane
2012-04-16 9:57 ` Ian Campbell
2012-04-16 12:55 ` [Xen-devel] " Remi Gacogne
2012-04-16 14:45 ` Lloyd Dizon
2012-04-16 14:57 ` [Xen-users] " Ian Campbell
2012-04-17 7:41 ` [Xen-devel] " Lloyd Dizon
2012-04-17 8:16 ` [Xen-users] " Ian Campbell
2012-04-17 9:35 ` [Xen-devel] " Lloyd Dizon
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