u-boot/doc/README.trace

18 The trace feature uses GCC's instrument-functions feature to trace all
24 which extracts useful information from it. The resulting trace output
50 Run sandbox, wait for a bit of trace information to appear, and then capture
51 a trace:
59 trace: enabled
65 =>trace stats
73 =>trace stats
81 =>trace calls 0 e00000
93 =>sb save host 0 trace 0 ${profoffset}
98 Then run proftool to convert the trace information to ftrace format.
100 $ ./sandbox/tools/proftool -m sandbox/System.map -p trace dump-ftrace >trace.txt
104 $ pytimechart trace.txt
106 Using this tool you can zoom and pan across the trace, with the function
115 		Enables the trace feature in U-Boot.
118 		Enables the trace command.
121 		Size of trace buffer to allocate for U-Boot. This buffer is
130 		Size of 'early' trace buffer. Before U-Boot has relocated
131 		it doesn't have a proper trace buffer. On many boards
132 		you can define an area of memory to use for the trace
133 		buffer until the 'real' trace buffer is available after
138 		Address of early trace buffer
150 Collecting Trace Data
153 When you run U-Boot on your board it will collect trace data up to the
154 limit of the trace buffer size you have specified. Once that is exhausted
157 Collecting trace data has an affect on execution time/performance. You
174 OS. There is useful trace data in the execution of that bootm
175 command. Therefore this implementation provides a way to collect trace
179 collects the trace data and writes it somewhere.
181 Trace data collection relies on a microsecond timer, accesed through
187 __attribute__((no_instrument_function)) so that the trace library can
194 The trace command has variable sub-commands:
209 		Dump function call trace into buffer
222 		Base address of trace output buffer
225 		Offset of first unwritten byte in trace output buffer
228 		Size of trace output buffer
230 All of these are set by the 'trace calls' command.
232 These variables keep track of the amount of data written to the trace
233 output buffer by the 'trace' command. The trace commands which write data
238 	trace funclist 10000 e00000
239 	trace calls
246 		is a useful time to write the trace data to the host for
250 Writing Out Trace Data
253 Once the trace data is in an output buffer in memory there are various ways
257 fakegocmd=trace pause; usb start; set autoload n; bootp;
258 	trace calls 10000000 1000000;
262 a trace log to address 10000000 and sends it to a host machine using
267 Converting Trace Output Data
270 The trace output data is kept in a binary format which is not documented
273 This tool must be given the U-Boot map file and the trace data received
281 		Specifiy profile/trace file
289 Viewing the Trace Data
311 3. Collect the trace information as descibed above. Use this to find where
323 Configuring Trace
329 The maximum depth reached is recorded and displayed by the 'trace stats'
337 run-time configuration options for trace.
341 - Trace filter to select which functions are recorded
343 - Better control over trace depth
344 - Compression of trace information