Re: Wiki docs on counting and tracing KVM perf events

[Jes Sorensen <Jes.Sorensen@redhat.com>]

On 05/13/10 16:57, Avi Kivity wrote:
> On 05/13/2010 05:35 PM, Stefan Hajnoczi wrote:
>> How to count and trace KVM perf events:
>>
>> http://www.linux-kvm.org/page/Perf_events
>>
>> I want to draw attention to this because traditional kvm_stat and
>> kvm_trace use has been moving over to the debugfs based tracing
>> mechanisms.  Perhaps we can flesh out documentation and examples of
>> common perf event usage.
>>
>>    
> 
> Two things are missing to make this really useful:
> 
> - a continuously updating difference mode like kvm_stat
> - subevents; for example kvm:kvm_exit is an aggregate of all exit types
> that can be split using filters to show individual exit reason statistics

Third missing item, which I find really useful:
- run once spit out raw counters

For some operations, like file system benchmarking, it is useful to
sample the counters before and after and then divide the raw number of
events by the number of IOPS performed by the benchmark. If perf spits
out events/sec it's kinda hard to get this.

Cheers,
Jes