On 03/31/2010 07:53 PM, Jiaqing Du wrote:
Hi, We have some code about performance profiling in KVM. They are outputs of a school project. Previous discussions in KVM, Perfmon2, and Xen mailing lists helped us a lot. The code are NOT in a good shape and are only used to demonstrated the feasibility of doing performance profiling in KVM. Feel free to use it if you want.
Performance monitoring is an important feature for kvm. Is there any chance you can work at getting it into good shape?
We categorize performance profiling in a virtualized environment into two types: *guest-wide profiling* and *system-wide profiling*. For guest-wide profiling, only the guest is profiled. KVM virtualizes the PMU and the user runs a profiler directly in the guest. It requires no modifications to the guest OS and the profiler running in the guest. For system-wide profiling, both KVM and the guest OS are profiled. The results are similar to what XenOprof outputs. In this case, one profiler running in the host and one profiler running in the guest. Still it requires no modifications to the guest and the profiler running in it.
Can your implementation support both simultaneously?
For guest-wide profiling, there are two possible places to save and restore the related MSRs. One is where the CPU switches between guest mode and host mode. We call this *CPU-switch*. Profiling with this enabled reflects how the guest behaves on the physical CPU, plus other virtualized, not emulated, devices. The other place is where the CPU switches between the KVM context and others. Here KVM context means the CPU is executing guest code or KVM code, both kernel space and user space. We call this *domain-switch*. Profiling with this enabled discloses how the guest behaves on both the physical CPU and KVM. (Some emulated operations are really expensive in a virtualized environment.)
Which method do you use? Or do you support both? Note disclosing host pmu data to the guest is sometimes a security issue. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. -- 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
