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Date: Fri, 03 Feb 2012 02:43:17 +0800
From: Xiao Guangrong <xiaoguangrong.eric@...il.com>
To: Avi Kivity <avi@...hat.com>
CC: Marcelo Tosatti <mtosatti@...hat.com>, Ingo Molnar <mingo@...e.hu>,
Arnaldo Carvalho de Melo <acme@...radead.org>,
Stefan Hajnoczi <stefanha@...il.com>,
LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] KVM: x86: add tracepoints to trace mmio begin
and complete
On 02/03/2012 02:27 AM, Xiao Guangrong wrote:
> 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@...ux.vnet.ibm.com>
>>>>>
>>>>> '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...)
And the pio result:
1: Using kvm_mmio_begin/end:
# ./perf kvm-events report --event ioport --key time
Warning: Error: expected type 5 but read 4
Warning: Error: expected type 5 but read 0
Warning: unknown op '}'
Analyze events for all VCPUs:
IO Port Access Samples Samples% Time% Avg time
0x1f0:PIN 3 0.00% 0.02% 115.91us ( +- 12.55% )
0xc026:PIN 645 0.32% 4.55% 105.21us ( +- 59.73% )
0x64:PIN 114 0.06% 0.14% 18.63us ( +- 5.02% )
0xc022:PIN 457 0.23% 0.53% 17.18us ( +- 4.15% )
0x60:PIN 114 0.06% 0.11% 14.56us ( +- 7.16% )
0xc000:POUT 22512 11.30% 17.21% 11.41us ( +- 6.84% )
0x1f7:PIN 30044 15.08% 22.53% 11.19us ( +- 10.37% )
0xc024:POUT 6 0.00% 0.00% 10.60us ( +- 54.28% )
......
2: kvm_mmio_begin/end is not used:
# ./perf kvm-events report --event ioport --key time
Warning: Error: expected type 5 but read 4
Warning: Error: expected type 5 but read 0
Warning: unknown op '}'
Analyze events for all VCPUs:
IO Port Access Samples Samples% Time% Avg time
0x1f0:PIN 3 0.00% 0.02% 118.37us ( +- 12.65% )
0xc026:PIN 645 0.32% 3.54% 107.89us ( +- 58.26% )
0x64:PIN 114 0.06% 0.13% 23.04us ( +- 6.44% )
0xc022:PIN 457 0.23% 0.48% 20.63us ( +- 3.65% )
0x60:PIN 114 0.06% 0.10% 17.70us ( +- 6.41% )
0xc000:POUT 22512 11.30% 16.19% 14.14us ( +- 6.27% )
0x1f7:PIN 30044 15.08% 21.18% 13.85us ( +- 8.39% )
0xc024:POUT 6 0.00% 0.00% 13.09us ( +- 47.40% )
......
The time of case 1 is calculated by kvm_pio -> kvm_mmio_done
The time of case 2 is calculated by kvm_pio -> kvm_entry
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