On 09/03/2012 07:07 PM, Avi Kivity wrote: > On 08/27/2012 12:51 PM, Dong Hao wrote: >> From: Xiao Guangrong <xiaoguangr...@linux.vnet.ibm.com> >> >> 'perf kvm stat record/report' will use kvm_exit and kvm_mmio(read...) to >> calculate mmio read emulated time for the old kernel, in order to trace >> mmio read event more exactly, we add kvm_mmio_begin to trace the time when >> mmio read begins, also, add kvm_io_done to trace the time when mmio/pio is >> completed >> > > Why is this so critical? > > If a lot of time is spent in in-kernel mmio, then 'perf top' will report > it. Otherwise the time between kvm_exit and kvm_entry describes the > time spent in the host. Not all of it is mmio handling, but it is quite > close.
I have done some test, the new events can get more exact result, this is a example in my slides: the event handled time calculated by old events is: 0.000066(s) calculated by new events, the result is: 0.000005(s). So, i think it is worth introducing these new events. But if you do not care it or think these events are duplicate with current events or unmaintainable, i do not have strong opinion on that. Please let me know, i will drop them in the next version. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
