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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 |