| 1 | |
| 2 | LTTng usertrace package |
| 3 | |
| 4 | Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> |
| 5 | March 2006 |
| 6 | |
| 7 | This package contains all the user space headers and c files necessary to make |
| 8 | your application and library trace through an active LTTng tracer. Here is a |
| 9 | short quickstart guide of it. |
| 10 | |
| 11 | Here are the currently supported architectures : |
| 12 | x86 |
| 13 | (please add the ltt_trace_generic and ltt_register_generic system calls to |
| 14 | other architectures as you need them : it will work magically) |
| 15 | |
| 16 | * Compile your kernel with the latest LTTng patch. Make sure the option |
| 17 | "Allow tracing from userspace" is _active_! |
| 18 | See the QUICKSTART guide at http://ltt.polymtl.ca/ for details about how to |
| 19 | setup a working tracer and viewer. See the genevent installation step : it is |
| 20 | required for method #2 below. |
| 21 | |
| 22 | * Extract the latest ltt-usertrace archive : |
| 23 | su |
| 24 | cd /usr/src |
| 25 | wget http://ltt.polymtl.ca/packages/ltt-usertrace-x.x.tar.gz |
| 26 | gzip -cd ltt-usertrace-x.x.tar.gz | tar xvof - |
| 27 | |
| 28 | * Build the sample programs and install the headers and librairies into your |
| 29 | system : |
| 30 | su |
| 31 | cd /usr/src/ltt-usertrace |
| 32 | make |
| 33 | make install |
| 34 | |
| 35 | Feel free to look at the sample programs and the Makefile : they demonstrate |
| 36 | very well the features of the usertrace package and how to use them. |
| 37 | |
| 38 | * There are three ways to trace information from your application. The choice |
| 39 | will principally depend on the trace data rate. |
| 40 | |
| 41 | 1) Easy way, but slow (printf style) |
| 42 | See sample-printf.c for code example. |
| 43 | |
| 44 | - Add the following statements to your program source (the define must come |
| 45 | _before_ the includes!) : |
| 46 | |
| 47 | #define LTT_TRACE |
| 48 | #define LTT_BLOCKING 1 |
| 49 | #include <ltt/ltt-facility-user_generic.h> |
| 50 | #include <ltt/ltt-facility-custom-user_generic.h> |
| 51 | |
| 52 | Note the define of LTT_BLOCKING to 1 : if a trace buffer is full, your |
| 53 | application will block. The default of this parameter is 0 (non blocking) : |
| 54 | events are lost when trace buffer is full. The choice is up to you. |
| 55 | |
| 56 | - Add something like the following sample line in your code. Note that this is a |
| 57 | very standard format string, this is only a suggested presentation. |
| 58 | |
| 59 | trace_user_generic_slow_printf("in: %s at: %s:%d: Counter value is: %u.", |
| 60 | __FILE__, __func__, __LINE__, count); |
| 61 | |
| 62 | - Compile your application with at least these parameters to gcc (it is splitted |
| 63 | on two lines, joined by a "\") : |
| 64 | gcc -D LTT_SHOW_DEBUG -I /usr/src/usertrace-generic -o myapp myapp.c \ |
| 65 | /usr/src/usertrace-generic/ltt-facility-loader-user_generic.c |
| 66 | |
| 67 | To see what the final result looks like : |
| 68 | - Start tracing |
| 69 | - Start your application |
| 70 | ** You should see the following message when your program starts and the |
| 71 | LTT_SHOW_DEBUG is defined : |
| 72 | "LTT : ltt-facility-user_generic init in userspace" |
| 73 | If you don't then you forgot to compile the facility loader in your |
| 74 | application. If you find this output annoying, you can remove the |
| 75 | "-D LTT_SHOW_DEBUG" gcc parameter, which will make the facility loader |
| 76 | silent. |
| 77 | - Stop tracing |
| 78 | Then, to see only the user_generic events : |
| 79 | lttv -m textDump -t /tmp/trace1 -e "event.facility=user_generic" |
| 80 | |
| 81 | It will show : |
| 82 | user_generic.slow_printf: 35885.922829472 (/cpu_0), 15521, 7453, SYSCALL { "in: sample-printf.c at: main:18: Counter value is: 0." } |
| 83 | user_generic.slow_printf: 35886.925685289 (/cpu_0), 15521, 7453, SYSCALL { "in: sample-printf.c at: main:18: Counter value is: 1." } |
| 84 | ... |
| 85 | |
| 86 | |
| 87 | |
| 88 | 2) The second way to log events is still easy. The advantage is that it |
| 89 | will make it easier to identify your data in the trace viewer afterward. |
| 90 | Please read the comments in method 1) explained previously, as they |
| 91 | are not repeated here. |
| 92 | See sample.c and sample-thread-slow.c for code example. |
| 93 | |
| 94 | - Go to the ltt-usertrace directory |
| 95 | su |
| 96 | cd /usr/src/ltt-usertrace |
| 97 | |
| 98 | - Create your own facility (i.e. user_myfacility.xml). |
| 99 | See the ones available in /usr/share/LinuxTraceToolkitViewer/facilities for |
| 100 | examples. |
| 101 | You facility _must_ be named following this standard : "user_*", where * is |
| 102 | whatever you like. If it is not, it will be rejected by the kernel with a |
| 103 | Operation not permitted (can be seen with the -D LTT_SHOW_DEBUG compilation |
| 104 | parameter). |
| 105 | |
| 106 | user_myfacility.xml: |
| 107 | |
| 108 | <?xml version="1.0"?> |
| 109 | <facility name="user_myfacility"> |
| 110 | <description>Sample facility</description> |
| 111 | <event name="myevent"> |
| 112 | <description>Sample event</description> |
| 113 | <field name="file"><string></field> |
| 114 | <field name="function"><string></field> |
| 115 | <field name="line"><int></field> |
| 116 | <field name="firstval"><long></field> |
| 117 | <field name="secondval"><pointer></field> |
| 118 | </event> |
| 119 | </facility> |
| 120 | |
| 121 | - AN IMPORTANT STEP FOLLOWS : |
| 122 | *copy* the user_myfacility.xml file in your system : |
| 123 | su |
| 124 | cp user_myfacility.xml /usr/share/LinuxTraceToolkitViewer/facilities |
| 125 | |
| 126 | - Use genevent to create the c code and headers : |
| 127 | su |
| 128 | cd /tmp |
| 129 | mkdir genevent |
| 130 | cd genevent |
| 131 | for a in /usr/share/LinuxTraceToolkitViewer/facilities/user_*.xml; |
| 132 | do /usr/local/bin/genevent $a; |
| 133 | done |
| 134 | cd /usr/src/usertrace-generic |
| 135 | cp /tmp/genevent/*load* . |
| 136 | cd ltt |
| 137 | cp /tmp/genevent/ltt-facility-id-user_myfacility.h . |
| 138 | cp /tmp/genevent/ltt-facility-user_myfacility.h . |
| 139 | cd .. |
| 140 | make install |
| 141 | |
| 142 | - Add the following statements to your program source (the define must come |
| 143 | _before_ the includes!) : |
| 144 | |
| 145 | #define LTT_TRACE |
| 146 | #define LTT_BLOCKING 1 |
| 147 | #include <ltt/ltt-facility-user_myfacility.h> |
| 148 | |
| 149 | - Add a call following the trace_user_myfacility_myevent function found in |
| 150 | /usr/include/ltt/ltt-facility-user_myfacility.h in your program. |
| 151 | For instance : |
| 152 | trace_user_myfacility_myevent(__FILE__, __func__, __LINE__, 1234, (void*)0xF0F0F0F0); |
| 153 | |
| 154 | - Compile your application with at least these parameters to gcc (it is splitted |
| 155 | on two lines, joined by a "\") : |
| 156 | gcc -I /usr/src/usertrace-generic -o myapp myapp.c \ |
| 157 | /usr/src/usertrace-generic/ltt-facility-loader-user_myfacility.c |
| 158 | |
| 159 | To see what the final result looks like : |
| 160 | - Start tracing |
| 161 | - Start your application |
| 162 | - Stop tracing |
| 163 | Then, to see only the user_myfacility events : |
| 164 | lttv -m textDump -t /tmp/trace1 -e "event.facility=user_myfacility" |
| 165 | |
| 166 | It will show, for example : |
| 167 | user_myfacility.myevent: 39507.805584526 (/cpu_1), 15829, 15736, SYSCALL { "myapp.c", "main", 8, 1234, 0xf0f0f0f0 } |
| 168 | |
| 169 | |
| 170 | 3) The third way to trace information from your application |
| 171 | |
| 172 | This method is cleary the _FASTEST_. It is principally I/O (disk and memory) |
| 173 | bound. It will create a companion process for each of you program's thread which |
| 174 | will dump the tracing information into /tmp/ltt-usertrace. |
| 175 | |
| 176 | See sample-highspeed.c and sample-thread-fast.c for code example. |
| 177 | |
| 178 | - Add the following statements to your program source (the define must come |
| 179 | _before_ the includes!) : |
| 180 | |
| 181 | #define LTT_TRACE |
| 182 | #define LTT_TRACE_FAST |
| 183 | #include <ltt/ltt-facility-user_myfacility.h> |
| 184 | |
| 185 | - Add a call following the trace_user_myfacility_myevent function found in |
| 186 | /usr/include/ltt/ltt-facility-user_myfacility.h in your program. |
| 187 | For instance : |
| 188 | trace_user_myfacility_myevent(__FILE__, __func__, __LINE__, 1234, (void*)0xF0F0F0F0); |
| 189 | |
| 190 | - Compile your application with at least these parameters to gcc (it is splitted |
| 191 | on two lines, joined by a "\") : |
| 192 | gcc -lltt-usertrace-fast -I /usr/src/usertrace-generic -o myapp myapp.c \ |
| 193 | /usr/src/usertrace-generic/ltt-facility-loader-user_myfacility.c |
| 194 | |
| 195 | It requires a supplementary operation when you take the trace : |
| 196 | - Start tracing (with lttctl) |
| 197 | - Start your application |
| 198 | - Let your application run... |
| 199 | - Stop tracing |
| 200 | - Move or copy /tmp/ltt-usertrace info your trace. |
| 201 | i.e., if your trace is in /tmp/trace1 : |
| 202 | su |
| 203 | mv /tmp/ltt-usertrace /tmp/trace1 |
| 204 | |
| 205 | |
| 206 | Then, to see only the user_myfacility events : |
| 207 | lttv -m textDump -t /tmp/trace1 -e "event.facility=user_myfacility" |
| 208 | |
| 209 | It will show, for example : |
| 210 | user_myfacility.myevent: 39507.805584526 (/ltt-usertrace/process-26174.26174.39236180500380_0), 15829, 15736, USER_MODE { "myapp.c", "main", 8, 1234, 0xf0f0f0f0 } |
| 211 | |
| 212 | |
| 213 | |
| 214 | * Fun feature : function instrumentation |
| 215 | |
| 216 | Here is how to generate a full trace of you program function calls. |
| 217 | See the sample-instrument-fct.c example program. |
| 218 | |
| 219 | - Compile your application with at least these parameters to gcc (it is splitted |
| 220 | on two lines, joined by a "\") : |
| 221 | gcc -g -finstrument-functions \ |
| 222 | -lltt-instrument-functions -o myapp myapp.c |
| 223 | |
| 224 | To see what the final result looks like : |
| 225 | - Start tracing |
| 226 | - Start your application |
| 227 | - Stop tracing |
| 228 | Then, to see only the function_entry and function_exit events : |
| 229 | lttv -m textDump -t /tmp/trace1 -e "event.facility=user_generic & (event.name=function_entry & event.name=function_exit)" |
| 230 | |
| 231 | It will show, for example : |
| 232 | user_generic.function_entry: 59329.709939111 (/ltt-usertrace/process-26202.0.39949996866578_0), 19250, 18581, USER_MODE { 0x8048454, 0x80484c2 } |
| 233 | user_generic.function_exit: 59329.709944613 (/ltt-usertrace/process-26202.0.39949996866578_0), 19250, 18581, USER_MODE { 0x8048454, 0x80484c2 } |
| 234 | |
| 235 | you can then use (from the binutils package) |
| 236 | addr2line -e sample-instrument-fct -i -f 0x8048454 |
| 237 | Which shows : |
| 238 | test_function |
| 239 | /usr/src/usertrace-generic/sample-instrument-fct.c:12 |
| 240 | |
| 241 | The lookup in LTTV through libbfd has not been implemented yet. |
| 242 | |
| 243 | |