WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-users] ntpd under Xen Dom0 exhibits extremely high jitter/noise

To: Pasi Kärkkäinen <pasik@xxxxxx>, mail ignored <0.bugs.only.0@xxxxxxxxx>
Subject: Re: [Xen-users] ntpd under Xen Dom0 exhibits extremely high jitter/noise? runs stable/quiet under non-xen kernel.
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Sun, 17 Jan 2010 21:33:46 +0000
Cc: "Fajar A. Nugraha" <fajar@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Xen User-List <xen-users@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Sun, 17 Jan 2010 13:34:40 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <20100117202255.GD17978@xxxxxxxxxxx>
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcqXstpeR2ecQXGJRKeiO/87j8R+9gACeVep
Thread-topic: [Xen-users] ntpd under Xen Dom0 exhibits extremely high jitter/noise? runs stable/quiet under non-xen kernel.
User-agent: Microsoft-Entourage/12.23.0.091001
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



_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users

<Prev in Thread] Current Thread [Next in Thread>