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