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87 lines
2.3 KiB
Plaintext
87 lines
2.3 KiB
Plaintext
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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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