1 Intel Branch Trace Store 2 ======================== 3 4 Overview 5 ======== 6 7 Intel BTS could be regarded as a predecessor to Intel PT and has some 8 similarities because it can also identify every branch a program takes. A 9 notable difference is that Intel BTS has no timing information and as a 10 consequence the present implementation is limited to per-thread recording. 11 12 While decoding Intel BTS does not require walking the object code, the object 13 code is still needed to pair up calls and returns correctly, consequently much 14 of the Intel PT documentation applies also to Intel BTS. Refer to the Intel PT 15 documentation and consider that the PMU 'intel_bts' can usually be used in 16 place of 'intel_pt' in the examples provided, with the proviso that per-thread 17 recording must also be stipulated i.e. the --per-thread option for 18 'perf record'. 19 20 21 perf record 22 =========== 23 24 new event 25 --------- 26 27 The Intel BTS kernel driver creates a new PMU for Intel BTS. The perf record 28 option is: 29 30 -e intel_bts// 31 32 Currently Intel BTS is limited to per-thread tracing so the --per-thread option 33 is also needed. 34 35 36 snapshot option 37 --------------- 38 39 The snapshot option is the same as Intel PT (refer Intel PT documentation). 40 41 42 auxtrace mmap size option 43 ----------------------- 44 45 The mmap size option is the same as Intel PT (refer Intel PT documentation). 46 47 48 perf script 49 =========== 50 51 By default, perf script will decode trace data found in the perf.data file. 52 This can be further controlled by option --itrace. The --itrace option is 53 the same as Intel PT (refer Intel PT documentation) except that neither 54 "instructions" events nor "transactions" events (and consequently call 55 chains) are supported. 56 57 To disable trace decoding entirely, use the option --no-itrace. 58 59 60 dump option 61 ----------- 62 63 perf script has an option (-D) to "dump" the events i.e. display the binary 64 data. 65 66 When -D is used, Intel BTS packets are displayed. 67 68 To disable the display of Intel BTS packets, combine the -D option with 69 --no-itrace. 70 71 72 perf report 73 =========== 74 75 By default, perf report will decode trace data found in the perf.data file. 76 This can be further controlled by new option --itrace exactly the same as 77 perf script. 78 79 80 perf inject 81 =========== 82 83 perf inject also accepts the --itrace option in which case tracing data is 84 removed and replaced with the synthesized events. e.g. 85 86 perf inject --itrace -i perf.data -o perf.data.new
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