1.. SPDX-License-Identifier: GPL-2.0 2 3================ 4CoreSight - Perf 5================ 6 7 :Author: Carsten Haitzler <carsten.haitzler@arm.com> 8 :Date: June 29th, 2022 9 10Perf is able to locally access CoreSight trace data and store it to the 11output perf data files. This data can then be later decoded to give the 12instructions that were traced for debugging or profiling purposes. You 13can log such data with a perf record command like:: 14 15 perf record -e cs_etm//u testbinary 16 17This would run some test binary (testbinary) until it exits and record 18a perf.data trace file. That file would have AUX sections if CoreSight 19is working correctly. You can dump the content of this file as 20readable text with a command like:: 21 22 perf report --stdio --dump -i perf.data 23 24You should find some sections of this file have AUX data blocks like:: 25 26 0x1e78 [0x30]: PERF_RECORD_AUXTRACE size: 0x11dd0 offset: 0 ref: 0x1b614fc1061b0ad1 idx: 0 tid: 531230 cpu: -1 27 28 . ... CoreSight ETM Trace data: size 73168 bytes 29 Idx:0; ID:10; I_ASYNC : Alignment Synchronisation. 30 Idx:12; ID:10; I_TRACE_INFO : Trace Info.; INFO=0x0 { CC.0 } 31 Idx:17; ID:10; I_ADDR_L_64IS0 : Address, Long, 64 bit, IS0.; Addr=0x0000000000000000; 32 Idx:26; ID:10; I_TRACE_ON : Trace On. 33 Idx:27; ID:10; I_ADDR_CTXT_L_64IS0 : Address & Context, Long, 64 bit, IS0.; Addr=0x0000FFFFB6069140; Ctxt: AArch64,EL0, NS; 34 Idx:38; ID:10; I_ATOM_F6 : Atom format 6.; EEEEEEEEEEEEEEEEEEEEEEEE 35 Idx:39; ID:10; I_ATOM_F6 : Atom format 6.; EEEEEEEEEEEEEEEEEEEEEEEE 36 Idx:40; ID:10; I_ATOM_F6 : Atom format 6.; EEEEEEEEEEEEEEEEEEEEEEEE 37 Idx:41; ID:10; I_ATOM_F6 : Atom format 6.; EEEEEEEEEEEN 38 ... 39 40If you see these above, then your system is tracing CoreSight data 41correctly. 42 43To compile perf with CoreSight support in the tools/perf directory do:: 44 45 make CORESIGHT=1 46 47This requires OpenCSD to build. You may install distribution packages 48for the support such as libopencsd and libopencsd-dev or download it 49and build yourself. Upstream OpenCSD is located at: 50 51 https://github.com/Linaro/OpenCSD 52 53For complete information on building perf with CoreSight support and 54more extensive usage look at: 55 56 https://github.com/Linaro/OpenCSD/blob/master/HOWTO.md 57 58 59Kernel CoreSight Support 60------------------------ 61 62You will also want CoreSight support enabled in your kernel config. 63Ensure it is enabled with:: 64 65 CONFIG_CORESIGHT=y 66 67There are various other CoreSight options you probably also want 68enabled like:: 69 70 CONFIG_CORESIGHT_LINKS_AND_SINKS=y 71 CONFIG_CORESIGHT_LINK_AND_SINK_TMC=y 72 CONFIG_CORESIGHT_CATU=y 73 CONFIG_CORESIGHT_SINK_TPIU=y 74 CONFIG_CORESIGHT_SINK_ETBV10=y 75 CONFIG_CORESIGHT_SOURCE_ETM4X=y 76 CONFIG_CORESIGHT_CTI=y 77 CONFIG_CORESIGHT_CTI_INTEGRATION_REGS=y 78 79Please refer to the kernel configuration help for more information. 80 81Perf test - Verify kernel and userspace perf CoreSight work 82----------------------------------------------------------- 83 84When you run perf test, it will do a lot of self tests. Some of those 85tests will cover CoreSight (only if enabled and on ARM64). You 86generally would run perf test from the tools/perf directory in the 87kernel tree. Some tests will check some internal perf support like: 88 89 Check Arm CoreSight trace data recording and synthesized samples 90 Check Arm SPE trace data recording and synthesized samples 91 92Some others will actually use perf record and some test binaries that 93are in tests/shell/coresight and will collect traces to ensure a 94minimum level of functionality is met. The scripts that launch these 95tests are in the same directory. These will all look like: 96 97 CoreSight / ASM Pure Loop 98 CoreSight / Memcpy 16k 10 Threads 99 CoreSight / Thread Loop 10 Threads - Check TID 100 etc. 101 102These perf record tests will not run if the tool binaries do not exist 103in tests/shell/coresight/\*/ and will be skipped. If you do not have 104CoreSight support in hardware then either do not build perf with 105CoreSight support or remove these binaries in order to not have these 106tests fail and have them skip instead. 107 108These tests will log historical results in the current working 109directory (e.g. tools/perf) and will be named stats-\*.csv like: 110 111 stats-asm_pure_loop-out.csv 112 stats-memcpy_thread-16k_10.csv 113 ... 114 115These statistic files log some aspects of the AUX data sections in 116the perf data output counting some numbers of certain encodings (a 117good way to know that it's working in a very simple way). One problem 118with CoreSight is that given a large enough amount of data needing to 119be logged, some of it can be lost due to the processor not waking up 120in time to read out all the data from buffers etc.. You will notice 121that the amount of data collected can vary a lot per run of perf test. 122If you wish to see how this changes over time, simply run perf test 123multiple times and all these csv files will have more and more data 124appended to it that you can later examine, graph and otherwise use to 125figure out if things have become worse or better. 126 127This means sometimes these tests fail as they don't capture all the 128data needed. This is about tracking quality and amount of data 129produced over time and to see when changes to the Linux kernel improve 130quality of traces. 131 132Be aware that some of these tests take quite a while to run, specifically 133in processing the perf data file and dumping contents to then examine what 134is inside. 135 136You can change where these csv logs are stored by setting the 137PERF_TEST_CORESIGHT_STATDIR environment variable before running perf 138test like:: 139 140 export PERF_TEST_CORESIGHT_STATDIR=/var/tmp 141 perf test 142 143They will also store resulting perf output data in the current 144directory for later inspection like:: 145 146 perf-asm_pure_loop-out.data 147 perf-memcpy_thread-16k_10.data 148 ... 149 150You can alter where the perf data files are stored by setting the 151PERF_TEST_CORESIGHT_DATADIR environment variable such as:: 152 153 PERF_TEST_CORESIGHT_DATADIR=/var/tmp 154 perf test 155 156You may wish to set these above environment variables if you wish to 157keep the output of tests outside of the current working directory for 158longer term storage and examination. 159