Re: [Xen-devel] Performance numbers on PV-on-HVM

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 27 Sep 2010, Jagadish Nadimpalli wrote:
>       Also make sure that the PV interfaces are actually running, in
>       particular use the right name for the root device ('/dev/xvda',
>       if you are using 'hda' in your VM config file).
> 
> ??
> Could you please let me know where(config file) can I configure/verify the 
> name for root device.
> ??

A regular hvm config file should work fine, a disk configuration like
the following should work correctly:

disk = [ 'file:/root/images/lenny.img,hda:disk,w' ]

You can manually specify the root device using root= on the kernel
command line, for example root=/dev/xvda1.
If everything worked as expected, you should have something like this in
your dmesg:

blkfront: xvda: barriers enabled
    ide0: BM-DMA at 0xc140-0xc147
    ide1: BM-DMA at 0xc148-0xc14f
Probing IDE interface ide0...
 xvda: xvda1 xvda2 < xvda5 >

and you should have xvda under /dev but /dev/hda should be missing.

> Since I am testing network performance, I verified which network interface is 
> used in the PV-on-HVM VM. I found that there
> is no Ethernet device displayed in the lspci output of VM. Here is the lspci 
> output on PV-on-HVM VM. The Xen platform
> device is displayed in lspci. This means that the platform device is used as 
> PV driver in the PV-on-HVM guest. Please
> correct me if I am wrong.
> 
> ===========================================================
> 00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
> 00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
> 00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
> 00:01.2 USB Controller: Intel Corporation 82371SB PIIX3 USB [Natoma/Triton 
> II] (rev 01)
> 00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 01)
> 00:02.0 VGA compatible controller: Cirrus Logic GD 5446
> 00:03.0 Class ff80: XenSource, Inc. Xen Platform Device (rev 01)
> 00:05.0 Multimedia audio controller: Ensoniq ES1370 [AudioPCI]
> ===========================================================
> 
> 

this is a good sign: it means that the emulated pci network device has
been unplugged because the kernel setup netfront instead.

> > My machine has the following harware configuration.
> > (1) Chipset - Intel 82Q35
> > (2) Processor - Intel Core2 Duo CPU E8400 @ 3.00GHz
> >
> 
> Performance results might vary significantly depending on whether the
> cpu supports EPT or not. Could you please cat /proc/cpuinfo?
> If this cpu doesn't support EPT, it might be worth changing test
> hardware :)
> 
> ??
> Here is the cat /proc/cpuinfo output:
> ==================================================
> processor?????? : 0
> vendor_id?????? : GenuineIntel
> cpu family?????? : 6
> model?????? ?????? : 23
> model name?????? : Intel(R) Core(TM)2 Duo CPU???????? E8400?? @ 3.00GHz
> stepping?????? : 10
> cpu MHz?????? ?????? : 2992.566
> cache size?????? : 6144 KB
> physical id?????? : 0
> siblings?????? : 2
> core id?????? ?????? : 0
> cpu cores?????? : 1
> apicid?????? ?????? : 0
> initial apicid?????? : 0
> fpu?????? ?????? : yes
> fpu_exception?????? : yes
> cpuid level?????? : 2
> wp?????? ?????? : yes
> flags?????? ?????? : fpu de tsc msr pae mce cx8 apic sep mtrr mca cmov pat 
> clflush acpi mmx fxsr sse sse2 ss ht syscall nx lm
> constant_tsc rep_good pni est ssse3 cx16 sse4_1 hypervisor lahf_lm
> bogomips?????? : 5985.13
> 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?????? ?????? : 23
> model name?????? : Intel(R) Core(TM)2 Duo CPU???????? E8400?? @ 3.00GHz
> stepping?????? : 10
> cpu MHz?????? ?????? : 2992.566
> cache size?????? : 6144 KB
> physical id?????? : 0
> siblings?????? : 2
> core id?????? ?????? : 0
> cpu cores?????? : 1
> apicid?????? ?????? : 1
> initial apicid?????? : 1
> fpu?????? ?????? : yes
> fpu_exception?????? : yes
> cpuid level?????? : 2
> wp?????? ?????? : yes
> flags?????? ?????? : fpu de tsc msr pae mce cx8 apic sep mtrr mca cmov pat 
> clflush acpi mmx fxsr sse sse2 ss ht syscall nx lm
> constant_tsc rep_good pni est ssse3 cx16 sse4_1 hypervisor lahf_lm
> bogomips?????? : 5985.13
> clflush size?????? : 64
> cache_alignment?????? : 64
> address sizes?????? : 36 bits physical, 48 bits virtual
> power management:
> =============================================================
> ??


Sorry I have just realized that if you executed cat /proc/cpuinfo from
dom0 under xen the hap flag would be missing anyway.
Did xen printed out "Extended Page Tables (EPT)" at boot?
You can also check the xen output executing xm dmesg from dom0 after
host boot.

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