Hello!
I have following problem with KVM. I have quad-core processor
Xeon X7350 ( 8MB L2 cache ). The processor shares 4 MB L2 cache on two
cores. By XEN emulation the guest system have 4 MB cache at disposal.
xen guest: cat /proc/cpuinfo
processor : 3
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Xeon(R) CPU X7350 @ 2.93GHz
stepping : 11
cpu MHz : 2932.026
cache size : 4096 KB
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat clflush dts mmx fxsr sse sse2 ss syscall nx lm
constant_tsc pni ds_cpl cx16 xtpr lahf_lm
bogomips : 5865.67
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:
By KVM in the guest system have 2 MB cache at disposal.
kvm guest: cat /proc/cpuinfo
processor : 3
vendor_id : GenuineIntel
cpu family : 6
model : 6
model name : QEMU Virtual CPU version 0.9.1
stepping : 3
cpu MHz : 2932.026
cache size : 2048 KB
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca
cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx lm pni
bogomips : 5861.69
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:
On specific loads with the same number of processors, this difference
in the cache size leads to negative results. The productivity of the
KVM virtual machine shows 2 - 5 times worse results in comparison with
XEN virtual machine.
Host:
cpu: Intel(R) Xeon(R) CPU X7350 @ 2.93GHz
os: Centos 5.4 x86_64
kvm: kvm-83-105.el5_4.13
kernel: kernel-2.6.18-164.10.1.el5
kernel arch: x86_64
Guest:
os: Centos 5.4 x86_64
qemu command: /usr/libexec/qemu-kvm -S -M pc -m 4096 -smp 4 -name
centos -uuid 17136bf5-a7a3-0323-7e9b-90ec5aa06cdb
-no-kvm-pit-reinjection -monitor pty -pidfile
/var/run/libvirt/qemu//centos.pid -boot c -drive
file=/kvm/centos.img,if=virtio,index=0,boot=on,cache=none -net
nic,macaddr=52:54:00:43:81:4f,vlan=0,model=virtio -net
tap,fd=14,script=,vlan=0,ifname=vnet0 -serial pty -parallel none -usb
-vnc 127.0.0.1:0 -k en-us
Host CPU:
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Xeon(R) CPU X7350 @ 2.93GHz
stepping : 11
cpu MHz : 2931.962
cache size : 4096 KB
physical id : 3
siblings : 4
core id : 0
cpu cores : 4
apicid : 12
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall
nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 5863.92
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:
processor : 1
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Xeon(R) CPU X7350 @ 2.93GHz
stepping : 11
cpu MHz : 2931.962
cache size : 4096 KB
physical id : 8
siblings : 4
core id : 0
cpu cores : 4
apicid : 32
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall
nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm
bogomips : 5863.11
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:
processor : 2
vendor_id : GenuineIntel
cpu family : 6
cpu family : 6
model : 15
model name : Intel(R) Xeon(R) CPU X7350 @ 2.93GHz
stepping : 11
cpu MHz : 2931.962
cache size : 4096 KB
physical id : 4
siblings : 4
core id : 0
cpu cores : 4
apicid : 16
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall
nx lm constant_tsc pni monitor ds_cpl vm
x est tm2 cx16 xtpr lahf_lm
bogomips : 5863.10
clflush size : 64
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:
processor : 3
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Xeon(R) CPU X7350 @ 2.93GHz
stepping : 11
cpu MHz : 2931.962
cache size : 4096 KB
physical id : 15
siblings : 4
core id : 0
apicid : 60
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
x est tm2 cx16 xtpr lahf_lm
bogomips : 5863.19
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:
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