[all-commits] [llvm/llvm-project] c1b463: [trace] Add the definition of a TraceExporter plugin

[walter erquinigo via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c1b4632528cb405c9ef94cff90bf43afe688a899
      https://github.com/llvm/llvm-project/commit/c1b4632528cb405c9ef94cff90bf43afe688a899
  Author: Walter Erquinigo <wallace at fb.com>
  Date:   2021-07-26 (Mon, 26 Jul 2021)

  Changed paths:
    M lldb/include/lldb/Core/PluginManager.h
    A lldb/include/lldb/Target/TraceExporter.h
    M lldb/include/lldb/lldb-forward.h
    M lldb/include/lldb/lldb-private-interfaces.h
    M lldb/source/Commands/CommandObjectThread.cpp
    M lldb/source/Core/PluginManager.cpp
    M lldb/source/Plugins/CMakeLists.txt
    A lldb/source/Plugins/TraceExporter/CMakeLists.txt
    A lldb/source/Plugins/TraceExporter/ctf/CMakeLists.txt
    A lldb/source/Plugins/TraceExporter/ctf/CommandObjectThreadTraceExportCTF.cpp
    A lldb/source/Plugins/TraceExporter/ctf/CommandObjectThreadTraceExportCTF.h
    A lldb/source/Plugins/TraceExporter/ctf/TraceExporterCTF.cpp
    A lldb/source/Plugins/TraceExporter/ctf/TraceExporterCTF.h
    A lldb/source/Plugins/TraceExporter/ctf/TraceExporterCTFOptions.td
    M lldb/source/Target/CMakeLists.txt
    A lldb/source/Target/TraceExporter.cpp

  Log Message:
  -----------
  [trace] Add the definition of a TraceExporter plugin

Copying from the inline documentation:

```
Trace exporter plug-ins operate on traces, converting the trace data provided by an \a lldb_private::TraceCursor into a different format that can be digested by other tools, e.g. Chrome Trace Event Profiler.
Trace exporters are supposed to operate on an architecture-agnostic fashion, as a TraceCursor, which feeds the data, hides the actual trace technology being used.
```

I want to use this to make the code in https://reviews.llvm.org/D105741 a plug-in. I also imagine that there will be more and more exporters being implemented, as an exporter creates something useful out of trace data. And tbh I don't want to keep adding more stuff to the lldb/Target folder.

This is the minimal definition for a TraceExporter plugin. I plan to use this with the following commands:

- thread trace export <plug-in name> [plug-in specific args]
  - This command would support autocompletion of plug-in names
- thread trace export list
  - This command would list the available trace exporter plug-ins

I don't plan to create yet a "process trace export" because it's easier to start analyzing the trace of a given thread than of the entire process. When we need a process-level command, we can implement it.

I also don't plan to force each "export" command implementation to support multiple threads (for example, "thread trace start 1 2 3" or "thread trace start all" operate on many threads simultaneously). The reason is that the format used by the exporter might or might not support multiple threads, so I'm leaving this decision to each trace exporter plug-in.

Differential Revision: https://reviews.llvm.org/D106501