>> >> >hi, >> > Can someone briefly explain what the cr3-cache feature on intel VT >> >processors is and how it is used to improve performance in >> >paravirtualization. >> >> In short, this is a unique Intel VT feature that supposed to save vmexit >> on cr3 switch. The vmexit operation is quite expensive at the moment >> (something like 2-5 ms!). PV kernels can use this feature by sharing > ^^^^^^^^^^^^^^^^^^^^^^^^ > >Where do you measured this unbelievable large number? On AMD-V I >measured around 2400 processor cycles for a VMEXIT/VMENTRY roundtrip. I >would really really wonder if Intel-VT is that slow...
Intel is indeed slower than AMD with this one. I didn't measure such roundtrip specifically. We usually see that the VMETNRY/VMEXIT cycle limits our performance (for io/mmio,..) On Intel core duo we cannot get more than 150k-200k VMEXITS per second for regular guest doing extensive IO. Anyway 2ms for a 2.4G processor equals 4800 cycles so it's not that far. > >Joerg > >-- >Joerg Roedel >Operating System Research Center >AMD Saxony LLC & Co. KG > ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ kvm-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/kvm-devel
