On Thursday 11 March 2010 15:36:01 Avi Kivity wrote: > On 03/11/2010 09:20 AM, Sheng Yang wrote: > > Currently we can only get the cpu_stat of whole guest as one. This patch > > enhanced cpu_stat with more detail, has guest_system and guest_user cpu > > time statistics with a little overhead. > > > > Signed-off-by: Sheng Yang<sh...@linux.intel.com> > > --- > > > > This draft patch based on KVM upstream to show the idea. I would split it > > into more kernel friendly version later. > > > > The overhead is, the cost of get_cpl() after each exit from guest. > > This can be very expensive in the nested virtualization case, so I > wouldn't like this to be in normal paths. I think detailed profiling > like that can be left to 'perf kvm', which only has overhead if enabled > at runtime.
Yes, that's my concern too(though nested vmcs/vmcb read already too expensive, they should be optimized...). The other concern is, perf alike mechanism would bring a lot more overhead compared to this. > For example you can put the code to note the cpl in a tracepoint which > is enabled dynamically. Yanmin have already implement "perf kvm" to support this. We are just arguing if a normal top-alike mechanism is necessary. I am also considering to make it a feature that can be disabled. But seems it make things complicate and result in uncertain cpustat output. -- regards Yang, Sheng -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
