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86 lines
2.3 KiB
86 lines
2.3 KiB
Intel Branch Trace Store |
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======================== |
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Overview |
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======== |
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Intel BTS could be regarded as a predecessor to Intel PT and has some |
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similarities because it can also identify every branch a program takes. A |
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notable difference is that Intel BTS has no timing information and as a |
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consequence the present implementation is limited to per-thread recording. |
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While decoding Intel BTS does not require walking the object code, the object |
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code is still needed to pair up calls and returns correctly, consequently much |
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of the Intel PT documentation applies also to Intel BTS. Refer to the Intel PT |
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documentation and consider that the PMU 'intel_bts' can usually be used in |
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place of 'intel_pt' in the examples provided, with the proviso that per-thread |
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recording must also be stipulated i.e. the --per-thread option for |
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'perf record'. |
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perf record |
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=========== |
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new event |
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--------- |
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The Intel BTS kernel driver creates a new PMU for Intel BTS. The perf record |
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option is: |
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-e intel_bts// |
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Currently Intel BTS is limited to per-thread tracing so the --per-thread option |
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is also needed. |
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snapshot option |
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--------------- |
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The snapshot option is the same as Intel PT (refer Intel PT documentation). |
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auxtrace mmap size option |
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----------------------- |
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The mmap size option is the same as Intel PT (refer Intel PT documentation). |
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perf script |
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=========== |
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By default, perf script will decode trace data found in the perf.data file. |
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This can be further controlled by option --itrace. The --itrace option is |
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the same as Intel PT (refer Intel PT documentation) except that neither |
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"instructions" events nor "transactions" events (and consequently call |
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chains) are supported. |
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To disable trace decoding entirely, use the option --no-itrace. |
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dump option |
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----------- |
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perf script has an option (-D) to "dump" the events i.e. display the binary |
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data. |
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When -D is used, Intel BTS packets are displayed. |
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To disable the display of Intel BTS packets, combine the -D option with |
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--no-itrace. |
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perf report |
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=========== |
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By default, perf report will decode trace data found in the perf.data file. |
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This can be further controlled by new option --itrace exactly the same as |
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perf script. |
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perf inject |
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=========== |
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perf inject also accepts the --itrace option in which case tracing data is |
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removed and replaced with the synthesized events. e.g. |
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perf inject --itrace -i perf.data -o perf.data.new
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