RE: [Xen-devel] Question about machine time delay in guest domains(Full virtualization)

["Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx>]

Hi Christie --

I don't know if you ever solved your problem or have been following time-related threads on xen-devel, but I suspect your problem stems from the fact that the virtual HPET has accuracy problems that are very noticeable with 64-bit Linux domains.  This is regardless of what you set for timer_mode.

 

To avoid this problem, you will need to set clocksource=pit in the /etc/grub.conf file of your hvm domain.  Hopefully there will be a better solution for this in the future.

 

Thanks,
Dan

-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx]On Behalf Of christie kumiko goto
Sent: Wednesday, January 09, 2008 5:33 AM
To: You, Yongkang
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] Question about machine time delay in guest domains(Full virtualization)

Hi, Yongkang,

Thanks so much!!

> Did you try if only creating 1 domains with 2 cpus?

I did the following 2 patterns.
  1) 2 domains with 2 vcpus (each domain shares 2 physical cpus)
  2) 4 domains with 2 vcpus (each domain shares 2 physical cpus)

>What's your platform and guest OS version?

Could you see the following info?

platform: x86_64
OS: RHEL5u1 2.6.18 (details are below)

--------------------
#uname -a
Linux DL360-dom0-RHEL5u1 2.6.18-53.el5xen #1 SMP Wed Oct 10 16:48:44 EDT
2007 x86_64 x86_64 x86_64 GNU/Linux

# xm info
host : DL360-dom0-RHEL5u1
release : 2.6.18-53.el5xen
version : #1 SMP Wed Oct 10 16:48:44 EDT 2007
machine : x86_64
nr_cpus : 2
nr_nodes : 1
sockets_per_node : 1
cores_per_socket : 2
threads_per_core : 1
cpu_mhz : 1866
hw_caps : bfebfbff:20000800:00000000:00000140:0004e3bd:00000000:00000001
total_memory : 16381
free_memory : 1
xen_major : 3
xen_minor : 1
xen_extra : .0-53.el5
xen_caps : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p
hvm-3.0-x86_64
xen_pagesize : 4096
platform_params : virt_start=0xffff800000000000
xen_changeset : unavailable
cc_compiler : gcc version 4.1.2 20070626 (Red Hat 4.1.2-14)
cc_compile_by : brewbuilder
cc_compile_domain : build.redhat.com
cc_compile_date : Wed Oct 10 16:30:57 EDT 2007
xend_config_format : 2

# cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Xeon(R) CPU E5320 @ 1.86GHz
stepping : 7
cpu MHz : 1866.730
cache size : 4096 KB
physical id : 0
siblings : 1
core id : 0
cpu cores : 1
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36 clflush dts
acpi mmx fxsr sse sse2 ss ht tm syscall lm constant_tsc pni monitor
ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 4669.03
clflush size : 64
cache_alignment : 64
address sizes : 36 bits physical, 48 bits virtual
power management:

processor : 1
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Xeon(R) CPU E5320 @ 1.86GHz
stepping : 7
cpu MHz : 1866.730
cache size : 4096 KB
physical id : 1
siblings : 1
core id : 0
cpu cores : 1
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36 clflush dts
acpi mmx fxsr sse sse2 ss ht tm syscall lm constant_tsc pni monitor
ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 4669.03
clflush size : 64
cache_alignment : 64
address sizes : 36 bits physical, 48 bits virtual
power management:

-------------------------

Thanks again,
I really appreciate your kind help!
;)

-Christi

2008/1/9, You, Yongkang <yongkang.you@xxxxxxxxx>:

On Tuesday, January 08, 2008 10:03 PM christie kumiko goto wrote:

> ------------------------------------------------------
> <<Environment>>
> -Host machine has 2 cores (core number 0-1)
> -Guest OSs: Full virtualization
>
> *test 1
> 4 domains share 2 core (each domain has 2 vcpu)
> ->result: actual test time : test time measured in guest domains = 4:1
>
> *test 2
> 2 domains share 1 core and the other 2 domains share the other 1 core.
> ->result: actual test time : test time measured in guest domains = 2:1
> ------------------------------------------------------

Hi Christi,

Did you try if only creating 1 domains with 2 cpus?
What's your platform and guest OS version? There are some new configurations for guest timer, such as timer_mode=1/2/3 (default timer mode is 0). You can set it in the guest config file. For some new OS, we can use timer_mode=1/2 to make the timer more acccurate. But I am not sure if they can work in your testing.

Best Regards,
Yongkang You

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