Messages in this thread | | | Date | Fri, 03 Feb 2012 02:27:22 +0800 | From | Xiao Guangrong <> | Subject | Re: [PATCH v2 2/3] KVM: x86: add tracepoints to trace mmio begin and complete |
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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@linux.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...)
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