What platform timer does Xen say is initialised during boot? Possibly Xen's
'clocksource=' boot option could be used to select a different platform
timer exhibiting less jitter. Tbh I don't think we've ever done a detailed
analysis of ntp performance on Xen before -- this is something we might be
able to improve.
-- Keir
On 17/01/2010 20:22, "Pasi Kärkkäinen" <pasik@xxxxxx> wrote:
>
> Keir and others,
>
> Please check the table in the end of the mail below.. is there
> hypervisor (boot time) option to make it behave better for ntpd?
>
> -- Pasi
>
> On Sat, Jan 16, 2010 at 11:17:36AM -0800, mail ignored wrote:
>> On Thu, Jan 14, 2010 at 8:20 PM, Fajar A. Nugraha <fajar@xxxxxxxxx> wrote:
>>>> @ novell say it's xen & ntp
>>>> @ ntp say it's novell & xen
>>>> @ xen say it's novell & ntp
>>>>
>>
>>> That's why I suggested you use a workaround: use 2.6.18 kernel, either
>>> from RHEL or from xen.org :D
>>> If this works -> novell problem
>>> If this doesn't work -> xen problem
>>
>> On Sat, Jan 16, 2010 at 5:05 AM, Fajar A. Nugraha <fajar@xxxxxxxxx> wrote:
>>> You might want to try latest pv_ops as well
>>> (http://wiki.xensource.com/xenwiki/XenParavirtOps), which should be
>>> easier to work with Opensuse since the version number is close.
>>
>> it seems it's _not_ the kernel -- unless there's a coincident kernel
>> problem across source/vendor ...
>>
>> per
>> http://lists.xensource.com/archives/html/xen-devel/2009-12/msg01127.html
>> http://wiki.xensource.com/xenwiki/XenParavirtOps
>> http://wiki.xensource.com/xenwiki/Kernel.org_Linux_on_Xen
>>
>> cd /home/workspace && rm -rf linux-2.6-xen
>> git clone git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git
>> linux-2.6-xen
>> cd linux-2.6-xen
>> make clean
>> cp -a .config .config-old
>> wget -O .config
>> http://pasik.reaktio.net/xen/pv_ops-dom0-debug/config-2.6.31.4-pvops_dom0-x86
>> _64
>> make oldconfig
>> ...
>> Xen PCI Frontend (XEN_PCIDEV_FRONTEND) [N/m/y/?] (NEW) <-- m
>> ...
>> "IMQ" target support (NETFILTER_XT_TARGET_IMQ) [N/m/?] (NEW) <-- m
>> ...
>> IMQ (intermediate queueing device) support (IMQ) [M/y/?] (NEW) <--
>> [enter]
>> ...
>> Block-device tap backend driver (XEN_BLKDEV_TAP) [N/m/y/?] (NEW) <-- m
>> ...
>>
>> make bzImage
>> make modules
>> make modules_install
>> strip vmlinux -o vmlinux-stripped
>> gzip vmlinux-stripped -c > vmlinuz-gzipped
>>
>> ls -al .config \
>> System.map \
>> arch/x86/boot/bzImage \
>> vmlinux \
>> vmlinux-stripped \
>> vmlinuz-gzipped
>>
>> cp -a .config /boot/config-2.6.31.6
>> cp -a System.map /boot/System.map-2.6.31.6
>> cp -a arch/x86/boot/bzImage /boot/vmlinuz-2.6.31.6
>> mkinitrd
>> ls -al /boot/*2.6.31.6*
>> -rw-r--r-- 1 root root 98510 2010-01-16 03:02 /boot/config-2.6.31.6
>> -rw-r--r-- 1 root root 21304611 2010-01-16 04:14 /boot/initrd-2.6.31.6
>> -rw-r--r-- 1 root root 1940879 2010-01-16 03:14 /boot/System.map-2.6.31.6
>> -rw-r--r-- 1 root root 3751936 2010-01-16 03:14 /boot/vmlinuz-2.6.31.6
>>
>>
>> vi /boot/grub/menu.lst
>> ...
>> title xen.git
>> root (hd0,0)
>> kernel /xen.gz loglvl=all loglvl_guest=all dom0_mem=1024M
>> vga=gfx-1280x1024x32 console=vga,com1 com1=57600,8n1
>> module /vmlinuz-2.6.31.6 root=/dev/VG0/ROOT rootfstype=ext4
>> rootflags=journal_checksum resume=/dev/VG0/SWAP nomodeset selinux=0
>> SELINUX_INIT=NO vga=0x31a console=tty0 console=xvc0,57600
>> module /initrd-2.6.31.6
>>
>> title xen.git DISABLED
>> root (hd0,0)
>> kernel /vmlinuz-2.6.31.6 root=/dev/VG_SVR/LV_SVR_DOM0_ROOT
>> rootfstype=ext4 rootflags=journal_checksum
>> resume=/dev/VG_SVR/LV_SVR_DOM0_SWAP nomodeset showopts splash=silent
>> selinux=0 SELINUX_INIT=NO elevator=cfq vga=0x31a console=tty0
>> console=ttyS0,57600n8
>> module /initrd-2.6.31.6
>> ...
>>
>>
>> boot to "xen.git"
>>
>> uname -a
>> Linux test 2.6.31.6 #1 SMP Sat Jan 16 03:14:19 PST 2010 x86_64
>> x86_64 x86_64 GNU/Linux
>> lsb_release -a
>> LSB Version:
>> core-2.0-noarch:core-3.2-noarch:core-4.0-noarch:core-2.0-x86_64:core-3.2-x86_
>> 64:core-4.0-x86_64:desktop-4.0-amd64:desktop-4.0-noarch:graphics-2.0-amd64:gr
>> aphics-2.0-noarch:graphics-3.2-amd64:graphics-3.2-noarch:graphics-4.0-amd64:g
>> raphics-4.0-noarch
>> Distributor ID: SUSE LINUX
>> Description: openSUSE 11.2 (x86_64)
>> Release: 11.2
>> Codename: n/a
>>
>> service ntp stop
>> rm /etc/adjtime /var/
>> rm /var/lib/ntp/drift/ntp.drift
>>
>> cat << EOF > /etc/sysconfig/clock
>> HWCLOCK="--utc"
>> SYSTOHC="yes"
>> TIMEZONE="America/Los_Angeles"
>> DEFAULT_TIMEZONE="US/Pacific"
>> EOF
>> hwclock --systohc --utc
>> service ntp start
>>
>> sntp clock.isc.org && date && hwclock --utc --show
>> 2010 Jan 16 04:37:09.000729 + 1.435060 +/- 0.028944 secs
>> Sat Jan 16 04:37:11 PST 2010
>> Sat 16 Jan 2010 04:37:11 AM PST -0.345191 seconds
>>
>> ... (wait ~ 6 hours) ...
>>
>> date
>> Sat Jan 16 11:01:42 PST 2010
>> ntpq -p -c rv
>> assID=0 status=06c4 leap_none, sync_ntp, 12 events, event_peer/strat_chg,
>> version="ntpd 4.2.4p8@xxxxxx Mon Dec 28 17:26:30 UTC 2009 (1)",
>> processor="x86_64", system="Linux/2.6.31.6", leap=00, stratum=2,
>> precision=-20, rootdelay=14.718, rootdispersion=135.995, peer=11390,
>> refid=66.220.9.122,
>> reftime=cefc89b2.a36f1342 Sat, Jan 16 2010 10:53:38.638, poll=6,
>> clock=cefc8b82.7e523feb Sat, Jan 16 2010 11:01:22.493, state=2,
>> offset=-115.130, frequency=-500.000, jitter=464.242, noise=29.343,
>> stability=154.680
>> remote refid st t when poll reach delay offset jitter
>>
=============================================================================>>
=
>> *clock.fmt.he.ne .PPS. 1 u 29 64 377 21.438 -811.68
>> 462.837
>> +otc2.psu.edu 129.6.15.29 2 u 7 64 377 109.399 -850.99
>> 470.522
>> +clock.isc.org .GPS. 1 u 7 64 377 21.440 -854.82
>> 468.274
>> +clock.sjc.he.ne .CDMA. 1 u 49 64 377 16.889 -780.55
>> 469.481
>> +zorro.sf-bay.or 216.218.254.202 2 u 59 64 377 20.366 -762.14
>> 458.947
>> +nist1.aol-ca.tr .ACTS. 1 u 38 64 377 16.260 -795.87
>> 463.170
>>
>> boot to "xen.git DISABLED"
>>
>> uname -a
>> Linux test 2.6.31.6 #1 SMP Sat Jan 16 09:14:19 PST 2010 x86_64 x86_64
>> x86_64 GNU/Linux
>>
>> service ntp stop
>> rm /etc/adjtime /var/
>> rm /var/lib/ntp/drift/ntp.drift
>> service ntp start
>>
>> ... (wait ~ 10 minutes) ...
>> date
>> Sat Jan 16 11:15:05 PST 2010
>> ntpq -p -c rv
>> assID=0 status=0664 leap_none, sync_ntp, 6 events, event_peer/strat_chg,
>> version="ntpd 4.2.4p8@xxxxxx Mon Dec 28 17:26:30 UTC 2009 (1)",
>> processor="x86_64", system="Linux/2.6.31.6", leap=00, stratum=2,
>> precision=-20, rootdelay=22.750, rootdispersion=975.184, peer=43091,
>> refid=66.220.9.122,
>> reftime=cefc8c7c.35ca466a Sat, Jan 16 2010 11:05:32.210, poll=6,
>> clock=cefc8eb9.25103a1f Sat, Jan 16 2010 11:15:05.144, state=3,
>> offset=27.534, frequency=0.000, jitter=6.740, noise=16.331,
>> stability=0.000
>> remote refid st t when poll reach delay offset jitter
>>
=============================================================================>>
=
>> *clock.fmt.he.ne .PPS. 1 u 4 64 377 18.112 10.541
>> 5.892
>> +otc2.psu.edu 147.84.59.145 2 u 64 64 377 101.103 12.106
>> 8.621
>> +clock.isc.org .GPS. 1 u 57 64 377 14.990 4.830
>> 9.622
>> +clock.sjc.he.ne .CDMA. 1 u 59 64 377 16.503 9.299
>> 9.440
>> +zorro.sf-bay.or 216.218.254.202 2 u 56 64 377 22.212 6.323
>> 11.031
>> +nist1.aol-ca.tr .ACTS. 1 u 60 64 377 17.076 14.316
>> 9.260
>>
>> in summary,
>>
>> kernel OS/distro xen timekeeping
>> ------------------------------------- --------------- ------- ------------
>> opensuse kernel-default-2.6.31.8-0.1 opensuse 11.2 (n/a) OK
>> opensuse kernel-default-2.6.32-41 opensuse 11.2 (n/a) OK
>> opensuse kernel-xen-2.6.31.8-0.1 opensuse 11.2 3.4.x NOISY/FAIL
>> opensuse kernel-xen-2.6.32-41 opensuse 11.2 3.4.x NOISY/FAIL
>> opensuse kernel-xen-2.6.31.8-0.1 opensuse 11.2 4.0.x NOISY/FAIL
>> opensuse kernel-xen-2.6.32-41 opensuse 11.2 4.0.x NOISY/FAIL
>> xen.git kernel-2.6.31.6 (pvops Dom0) opensuse 11.2 4.0.x NOISY/FAIL
>> xen.git kernel-2.6.31.6 opensuse 11.2 (n/a) OK
>>
>> i.e.,
>>
>> 3 different kernel versions, from two different vendors, have
>> low-noise/accurate timekeeping in NON-xen configs.
>>
>> boot any of those kernels with either v34x or v40x hypervisor in
>> place, and timekeeping suffers from unusably excessive jitter &
>> offset.
>>
>> _______________________________________________
>> Xen-users mailing list
>> Xen-users@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-users
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