Thanks for all this! I have a much bigger diff than you do.
21 Jul 14:54:07 ntpdate[3222]: ntpdate [email protected] Mon Jun 6 08:19:21 UTC 2016 (1) server 162.28.128.247, stratum 4, offset 0.001862, delay 0.02568 21 Jul 14:54:13 ntpdate[3222]: adjust time server 162.28.128.247 offset 0.001862 sec Hmm. Steal is low (.57%) and these both do have absolute share. -----Original Message----- From: Linux on 390 Port [mailto:[email protected]] On Behalf Of Christian Ehrhardt Sent: Thursday, July 21, 2016 1:30 AM To: [email protected] Subject: Re: [LINUX-390] Back to the future? That should do it for you: root@zla247: ntpdate -qv zla226 Here from two guests I have: yakkety-ntp-test2:~# ntpdate -qv yakkety-ntp-test1 21 Jul 08:29:34 ntpdate[7367]: ntpdate [email protected] Wed Jun 1 14:43:17 UTC 2016 (1) server 10.0.4.128, stratum 2, offset -0.000004, delay 0.02568 21 Jul 08:29:40 ntpdate[7367]: adjust time server 10.0.4.128 offset -0.000004 sec Christian Ehrhardt Software Engineer, Ubuntu Server Canonical Ltd On Thu, Jul 21, 2016 at 10:23 AM, Christian Ehrhardt < [email protected]> wrote: > And I almost forgot, since you have NTP running on both, you could > even setup one of them as NTP server for the other. > Which will give you a good way to get the offset between them using > the same way as described above. > > Christian Ehrhardt > Software Engineer, Ubuntu Server > Canonical Ltd > > On Thu, Jul 21, 2016 at 10:14 AM, Christian Ehrhardt < > [email protected]> wrote: > >> Hi, >> as Michael already mentioned the guests only have a offset they can >> store in the SIEBK. >> The clock of all your guests are ticking at the same pace, so you >> have no traditional different drifting due to different clocks on one system >> z box. >> If you have a difference between your Linux Guests that should be >> from your Linux actually setting time (and by that actually their offset). >> Given the permissions and access one could surely check the offsets >> of both guests, but that can be quite hard :-) >> >> For all other checks the issue will almost always be, that you would >> have to send a command to both at the same time which is impossible - >> so you can never compare most of the output if they just report "date" or >> such. >> But NTP which you already have running can help you to find if those >> two systems are apart. >> >> If you run "ntpq -pn" you get a list of servers as configured and an >> offset of your system too them. >> Now since your Linux guests are ticking at the same rate by the HW >> design, the offset to the same NTP peers should stay the same. >> >> If these offsets differ on your systems, something on that system has >> set time to be that offset. >> >> Also, if you continue debugging this I'd recommend trying to stay >> away from high level things like "date" as there are so many levels >> in between which could skew things. >> Write a minimal program calling STCKE should be way more reliable. >> And if you find the difference is always zero on STCKE level, but >> once you move to more abstracted functions like clock_gettimeofday / >> gettimeofday you can start debugging down that route. >> >> Kind Regards, >> Christian >> >> Christian Ehrhardt >> Software Engineer, Ubuntu Server >> Canonical Ltd >> >> On Thu, Jul 21, 2016 at 1:18 AM, Marcy Cortes < >> [email protected]> wrote: >> >>> I used a rexx exec to send commands to the console (secuser) that >>> looked like this: >>> >>> /**/ >>> address command "CP SEND ZLA226 date +'%d/%m/%Y %H:%M:%S:%6N'" >>> address command "CP SEND ZLA247 date +'%d/%m/%Y %H:%M:%S:%6N'" >>> >>> I would expect ZLA247's to be a bit later, but sometimes it shows >>> earlier. >>> >>> 18:04:34 20/07/2016 18:04:34:735597 >>> 18:04:34 20/07/2016 18:04:34:737365 >>> >>> 18:06:42 20/07/2016 18:06:42:317457 >>> 18:06:42 20/07/2016 18:06:42:325410 >>> >>> 18:08:50 20/07/2016 18:08:50:473232 >>> 18:08:50 20/07/2016 18:08:50:467567 >>> >>> 18:13:51 20/07/2016 18:13:51:055624 >>> 18:13:51 20/07/2016 18:13:51:037563 >>> >>> Hmm. >>> >>> -----Original Message----- >>> From: Linux on 390 Port [mailto:[email protected]] On Behalf >>> Of Michael Harding >>> Sent: Wednesday, July 20, 2016 2:47 PM >>> To: [email protected] >>> Subject: Re: [LINUX-390] Back to the future? >>> >>> In the guests' VMDBKs, in the SIEBK is stored the offset from the >>> hardware clock that gets loaded when the guest is run. I don't >>> recall the offset in the block. Unless that's different they should >>> both be seeing the same CPU clock. >>> >>> -- >>> Mike Harding >>> z/VM System Support >>> /sp >>> >>> >>> Linux on 390 Port <[email protected]> wrote on 07/20/2016 >>> 01:42:05 >>> PM: >>> >>> > From: Marcy Cortes <[email protected]> >>> > To: [email protected] >>> > Date: 07/20/2016 01:42 PM >>> > Subject: Back to the future? >>> > Sent by: Linux on 390 Port <[email protected]> >>> > >>> > So we have some servers that pass timestamps around to see how >>> > long they have to do something before throwing in the towel. >>> > >>> > They've recently put in some logging to debug some errors and have >>> > found some cases of going back in time. >>> > >>> > TmsSent 2016-07-20 07:40:07.000034 | TrapRx 2016-07-20 >>> > 07:40:06.000944 >>> > >>> > So back in time by nearly a second (.99909). >>> > >>> > These 2 servers are on the same VM system. Both run NTP. >>> > We know things get really out of whack without NTP. We had a bug >>> > where it didn't start and things got really confused. >>> > >>> > Could NTP be misbehaving? It was just patched. How can I prove >>> > that the clocks on the 2 servers have a different time so that I >>> > can ascertain if it is NTP or something else. >>> > >>> > >>> > >>> > Marcy >>> > >>> > >>> > >>> > ------------------------------------------------------------------ >>> > ---- For LINUX-390 subscribe / signoff / archive access >>> > instructions, send email to [email protected] with the >>> > message: INFO LINUX-390 or >>> visit >>> > http://www.marist.edu/htbin/wlvindex?LINUX-390 >>> > ------------------------------------------------------------------ >>> > ---- For more information on Linux on System z, visit >>> > http://wiki.linuxvm.org/ >>> > >>> >>> -------------------------------------------------------------------- >>> -- For LINUX-390 subscribe / signoff / archive access instructions, >>> send email to [email protected] with the message: INFO >>> LINUX-390 or visit >>> http://www.marist.edu/htbin/wlvindex?LINUX-390 >>> -------------------------------------------------------------------- >>> -- For more information on Linux on System z, visit >>> http://wiki.linuxvm.org/ >>> >>> -------------------------------------------------------------------- >>> -- For LINUX-390 subscribe / signoff / archive access instructions, >>> send email to [email protected] with the message: INFO >>> LINUX-390 or visit >>> http://www.marist.edu/htbin/wlvindex?LINUX-390 >>> -------------------------------------------------------------------- >>> -- For more information on Linux on System z, visit >>> http://wiki.linuxvm.org/ >>> >> >> > ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
