1Intel Branch Trace Store 2======================== 3 4Overview 5======== 6 7Intel BTS could be regarded as a predecessor to Intel PT and has some 8similarities because it can also identify every branch a program takes. A 9notable difference is that Intel BTS has no timing information and as a 10consequence the present implementation is limited to per-thread recording. 11 12While decoding Intel BTS does not require walking the object code, the object 13code is still needed to pair up calls and returns correctly, consequently much 14of the Intel PT documentation applies also to Intel BTS. Refer to the Intel PT 15documentation and consider that the PMU 'intel_bts' can usually be used in 16place of 'intel_pt' in the examples provided, with the proviso that per-thread 17recording must also be stipulated i.e. the --per-thread option for 18'perf record'. 19 20 21perf record 22=========== 23 24new event 25--------- 26 27The Intel BTS kernel driver creates a new PMU for Intel BTS. The perf record 28option is: 29 30 -e intel_bts// 31 32Currently Intel BTS is limited to per-thread tracing so the --per-thread option 33is also needed. 34 35 36snapshot option 37--------------- 38 39The snapshot option is the same as Intel PT (refer Intel PT documentation). 40 41 42auxtrace mmap size option 43----------------------- 44 45The mmap size option is the same as Intel PT (refer Intel PT documentation). 46 47 48perf script 49=========== 50 51By default, perf script will decode trace data found in the perf.data file. 52This can be further controlled by option --itrace. The --itrace option is 53the same as Intel PT (refer Intel PT documentation) except that neither 54"instructions" events nor "transactions" events (and consequently call 55chains) are supported. 56 57To disable trace decoding entirely, use the option --no-itrace. 58 59 60dump option 61----------- 62 63perf script has an option (-D) to "dump" the events i.e. display the binary 64data. 65 66When -D is used, Intel BTS packets are displayed. 67 68To disable the display of Intel BTS packets, combine the -D option with 69--no-itrace. 70 71 72perf report 73=========== 74 75By default, perf report will decode trace data found in the perf.data file. 76This can be further controlled by new option --itrace exactly the same as 77perf script. 78 79 80perf inject 81=========== 82 83perf inject also accepts the --itrace option in which case tracing data is 84removed and replaced with the synthesized events. e.g. 85 86 perf inject --itrace -i perf.data -o perf.data.new 87