On 02/03/2012 01:56 AM, Avi Kivity wrote:
> On 02/02/2012 07:55 PM, Xiao Guangrong wrote:
>> On 02/03/2012 01:36 AM, Avi Kivity wrote:
>>
>>> On 02/02/2012 07:27 PM, Xiao Guangrong wrote:
>>>> From: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
>>>>
>>>> 'perf kvm-events' 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_mmio_done to trace the time when mmio/pio is completed
>>>
>>> Previously, we discussed using the kvm_entry to do this. This reduces
>>> the number of tracepoints, and is backwards compatible. What was the
>>> conclusion?
>>>
>>
>>
>> Since using kvm_entry can cause lots of unnecessary calculated, these new two
>> tracepoints can let the result be exacter.
>
> Do you have numbers on the ratio between kvm_entry traces and
> kvm_mmio_begin/end traces?
>
1: Using kvm_mmio_begin/end:
# ./perf kvm-events report --event mmio
Warning: Error: expected type 5 but read 4
Warning: Error: expected type 5 but read 0
Warning: unknown op '}'
Analyze events for all VCPUs:
MMIO Access Samples Samples% Time% Avg time
0xfee00380:W 54926 58.45% 57.32% 3.90us ( +- 0.29% )
0xfee00300:W 12906 13.73% 28.70% 8.32us ( +- 0.50% )
0xfee00300:R 12906 13.73% 7.68% 2.23us ( +- 1.27% )
0xfee00310:W 12906 13.73% 6.07% 1.76us ( +- 1.05% )
0xfee00190:R 323 0.34% 0.23% 2.65us ( +- 2.85% )
Total Samples:93967, Total events handled time:374012.26us.
2: kvm_mmio_begin/end is not used:
# ./perf kvm-events report --event mmio
Warning: Error: expected type 5 but read 4
Warning: Error: expected type 5 but read 0
Warning: unknown op '}'
Analyze events for all VCPUs:
MMIO Access Samples Samples% Time% Avg time
0xfee00380:W 54926 58.45% 42.90% 3.90us ( +- 0.29% )
0xfee00300:W 12906 13.73% 21.48% 8.32us ( +- 0.50% )
0xfee00300:R 12906 13.73% 30.26% 11.72us ( +- 1.40% )
0xfee00310:W 12906 13.73% 4.54% 1.76us ( +- 1.05% )
0xfee00190:R 323 0.34% 0.82% 12.63us ( +- 2.85% )
Total Samples:93967, Total events handled time:499755.82us.
In this sample, the time of MMIO Read has big different,
in the case 1(new tracepoints), the time is calculated by kvm_mmio_begin -> kvm_mmio(read...)
in the case 2(existing tracepoints), the time is calculated by kvm_exit -> kvm_mmio(read...)
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