Re: Wiki docs on counting and tracing KVM perf events

[Avi Kivity <avi@redhat.com>]

On 05/20/2010 11:15 AM, Jes Sorensen wrote:
> 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.
>    

That's 'perf stat -a sleep 2'

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.