Ricardo Martins wrote:
Hi guys, I'm having a problem with kvm, my physical machine have 2 processor Xeon E5520, with 8 mb cache size, when i run "cat /proc/cpuinfo" the linux shows 16 processors equal. processor : 15 vendor_id : GenuineIntel cpu family : 6 model : 26 model name : Intel(R) Xeon(R) CPU E5520 @ 2.27GHz stepping : 5 cpu MHz : 1596.000 cache size : 8192 KB
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The problem is that when I run the same command on the virtual machine, Linux shows the processors with only 32 kb, I believe that anything is wrong. processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 6 model name : QEMU Virtual CPU version 0.9.1 stepping : 3 cpu MHz : 2266.575 cache size : 32 KB
> ....
On virtual Machine: linea:/# x86info x86info v1.21. Dave Jones 2001-2007 Found 1 CPU, but found 16d CPUs in MPTable. -------------------------------------------------------------------------- Family: 6 Model: 6 Stepping: 3 Type: 0 Brand: 0 CPU Model: Celeron / Mobile Pentium II Original OEM Feature flags: fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflsh mmx fxsr sse sse2 Extended feature flags: sse3 [31] [0] [2] [3] [4] [5] [6] [7] [8] [9] SYSCALL [13] [15] [16] xd [23] [24] em64t Cache info L1 Instruction cache: 32KB, 8-way associative. 64 byte line size. L1 Data cache: 32KB, 8-way associative. 64 byte line size. L2 unified cache: 2MB, sectored, 8-way associative. 64 byte line size. TLB info
KVM (or better: the QEMU part) injects a bogus CPU model (compare family/model/name), which is the same on all host CPUs. This helps with migration, because the CPU does not change. The cache size is also the same, as it is part of the "cpuid" command output. You can use other CPU models (like kvm64) for better base models, but the cache size will likely not match your host processor's one. For that purpose exists the "host" CPU model, which will (to some degree) simply push your host CPU model to the guest. For now this only affects the family/model/stepping/name values and the feature flags. I sent a patch to include the cache size when using -cpu host, but this has been n'acked because the benefit is not clear.
http://www.mail-archive.com/qemu-devel@xxxxxxxxxx/msg32718.html Do you have a use case for the cache size or is this just out of curiosity? -- Andre Przywara AMD-Operating System Research Center (OSRC), Dresden, Germany Tel: +49 351 448-3567-12 -- 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
