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Revamp the documentation for the new features, including a description of the new features and documentation for the trace command. Signed-off-by: Simon Glass <sjg@chromium.org>
164 lines
4.8 KiB
ReStructuredText
164 lines
4.8 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+:
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trace command
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=============
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Synopis
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-------
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::
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trace stats
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trace pause
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trace resume
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trace funclist [<addr> <size>]
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trace calls [<addr> <size>]
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Description
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-----------
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The *trace* command is used to control the U-Boot tracing system. It allows
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tracing to be paused and resumed, shows statistics for traces and provides a
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way to dump out the trace information.
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trace stats
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~~~~~~~~~~~
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This display tracing statistics, as follows:
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function sites
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Functions are binned as a way of reducing the amount of space needed to
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hold all the function information. This is controlled by FUNC_SITE_SIZE in
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the trace.h header file. The usual value is 4, which provides the finest
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granularity (assuming a minimum instruction size of 4 bytes) which means
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that every function can be resolved individually.
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function calls
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Total number of function calls, including those which were not traced due
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to buffer space. This count does not include functions which exceeded the
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depth limit.
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untracked function calls
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Total number of function calls which did not appear in the U-Boot image.
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This can happen if a function is called outside the normal code area.
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traced function calls
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Total number of function calls which were actually traced, i.e. are included
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in the recorded trace data.
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dropped due to overflow
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If the trace buffer was exhausted then this shows the number of records that
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were dropped. Try reducing the depth limit or expanding the buffer size.
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maximum observed call depth
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Maximum observed call depth while tracing.
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calls not traced due to depth
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Counts the number of function calls that were not recorded because they
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exceeded the maximum call depth.
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max function calls
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Maximum number of function calls which can be recorded in the trace buffer,
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given its size. Once `function calls` hits this value, recording stops.
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trace buffer
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Address of trace buffer
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call records
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Address of first trace record. This is near the start of the trace buffer,
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after the function-call counts.
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trace pause
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~~~~~~~~~~~
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Pauses tracing, so that no more data is added to the trace buffer.
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trace resume
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~~~~~~~~~~~~
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Resumes tracing, so that new function calls are added to the trace buffer if
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there is sufficient space.
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trace funclist [<addr> <size>]
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Dumps a list of functions into the provided buffer. The file uses a format
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specific to U-Boot: a header, following by the function offset and call count.
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If the address and size are not given, these are obtained from
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:ref:`develop/trace:environment variables`. In any case the environment
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variables are updated after the command runs.
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The resulting data should be written out to the host, e.g. using Ethernet or
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a filesystem. There are no tools provided to read this sdata.
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trace calls [<addr> <size>]
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Dumps a list of function calls into the provided buffer. The file uses a format
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specific to U-Boot: a header, following by the list of calls. The proftool
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tool can be used to convert this information ready for further analysis.
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Example
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-------
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::
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=> trace stats
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269,252 function sites
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38,025,059 function calls
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3 untracked function calls
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7,382,690 traced function calls
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17 maximum observed call depth
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15 call depth limit
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68,667,432 calls not traced due to depth
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22,190,112 max function calls
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trace buffer 6c000000 call records 6c20de78
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=> trace resume
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=> trace pause
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This shows that resuming the trace causes the buffer to overflow::
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=> trace stats
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269,252 function sites
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49,573,694 function calls
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3 untracked function calls
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22,190,112 traced function calls (8289848 dropped due to overflow)
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17 maximum observed call depth
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15 call depth limit
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68,667,432 calls not traced due to depth
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22,190,112 max function calls
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trace buffer 6c000000 call records 6c20de78
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=> trace funcs 30000000 0x100000
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Function trace dumped to 30000000, size 0x1e70
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This shows collecting and writing out the result trace data:
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::
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=> trace calls 20000000 0x10000000
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Call list dumped to 20000000, size 0xfdf21a0
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=> save mmc 1:1 20000000 /trace ${profoffset}
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File System is consistent
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file found, deleting
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update journal finished
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File System is consistent
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update journal finished
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266281376 bytes written in 18584 ms (13.7 MiB/s)
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From here you can use proftool to convert it:
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.. code-block:: bash
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tools/proftool -m System.map -t trace -o asc.fg dump-ftrace
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.. _`ACPI specification`: https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf
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