[PATCH v3 00/20] KVM: ARM64: Add guest PMU support

[cov@codeaurora.org (Christopher Covington)]

On 10/16/2015 12:55 AM, Wei Huang wrote:
> 
> 
> On 09/24/2015 05:31 PM, Shannon Zhao wrote:
>> This patchset adds guest PMU support for KVM on ARM64. It takes
>> trap-and-emulate approach. When guest wants to monitor one event, it
>> will be trapped by KVM and KVM will call perf_event API to create a perf
>> event and call relevant perf_event APIs to get the count value of event.
>>
>> Use perf to test this patchset in guest. When using "perf list", it
>> shows the list of the hardware events and hardware cache events perf
>> supports. Then use "perf stat -e EVENT" to monitor some event. For
>> example, use "perf stat -e cycles" to count cpu cycles and
>> "perf stat -e cache-misses" to count cache misses.
>>
>> Below are the outputs of "perf stat -r 5 sleep 5" when running in host
>> and guest.
>>
>> Host:
>>  Performance counter stats for 'sleep 5' (5 runs):
>>
>>           0.551428      task-clock (msec)         #    0.000 CPUs utilized            ( +-  0.91% )
>>                  1      context-switches          #    0.002 M/sec
>>                  0      cpu-migrations            #    0.000 K/sec
>>                 48      page-faults               #    0.088 M/sec                    ( +-  1.05% )
>>            1150265      cycles                    #    2.086 GHz                      ( +-  0.92% )
>>    <not supported>      stalled-cycles-frontend
>>    <not supported>      stalled-cycles-backend
>>             526398      instructions              #    0.46  insns per cycle          ( +-  0.89% )
>>    <not supported>      branches
>>               9485      branch-misses             #   17.201 M/sec                    ( +-  2.35% )
>>
>>        5.000831616 seconds time elapsed                                          ( +-  0.00% )
>>
>> Guest:
>>  Performance counter stats for 'sleep 5' (5 runs):
>>
>>           0.730868      task-clock (msec)         #    0.000 CPUs utilized            ( +-  1.13% )
>>                  1      context-switches          #    0.001 M/sec
>>                  0      cpu-migrations            #    0.000 K/sec
>>                 48      page-faults               #    0.065 M/sec                    ( +-  0.42% )
>>            1642982      cycles                    #    2.248 GHz                      ( +-  1.04% )
>>    <not supported>      stalled-cycles-frontend
>>    <not supported>      stalled-cycles-backend
>>             637964      instructions              #    0.39  insns per cycle          ( +-  0.65% )
>>    <not supported>      branches
>>              10377      branch-misses             #   14.198 M/sec                    ( +-  1.09% )
>>
>>        5.001289068 seconds time elapsed                                          ( +-  0.00% )
>>
> 
> Thanks for V3. One suggestion is to run more perf stress tests, such as
> "perf test". So we know the corner cases are covered as much as possible.

I'd also recommend Vince Weaver's perf_event_tests. It tests things like
signal-on-counter-overflow that I've never seen anywhere else (other than some
of my own code).

https://github.com/deater/perf_event_tests

Christopher Covington

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