You can add the option "-cpu host" to KVM. Then you get the same cache size information as your host has. Robert On 01/22/10 15:31, Hristo Tomov wrote: > 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: > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
