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43 lines
1.4 KiB
Markdown
43 lines
1.4 KiB
Markdown
# Tracing
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Cloud Hypervisor has a basic tracing infrastucture, particularly focussed on
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the tracing of the initial VM setup.
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## Usage
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To enabling tracing, build with "tracing" feature. When compiled without the
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feature the tracing is compiled out.
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```bash
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cargo build --features "tracing"
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```
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And then run Cloud Hypervisor as you wish, the trace will be written to the current directory as `cloud-hypervisor-<pid>.trace`. This is JSON file which you can inspect yourself.
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Alternatively you can use the provided script in
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`scripts/ch-trace-visualiser.py` to generate an SVG:
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For example:
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```bash
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scripts/ch-trace-visualiser.py cloud-hypervisor-39466.trace output.svg
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```
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## Tracing in the codebase
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There are existing tracepoints in the code base; extra ones can be added for
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more detailed tracing.
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The `tracer::trace_scoped!()` macro is used to add the current existing scope
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appears as a block in the trace. Other than providing a useful name for the
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event nothing else is required from the developer.
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The `tracer::start()` and `tracer::end()` functions are already in place for
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generating traces of the boot. These can be relocated for focus tracing on a
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narrow part of the code base.
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A `tracer::trace_point!()` macro is also provided for an instantaneous trace
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point however this is not in use in the code base currently nor is handled by
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the visualisation script due to the difficulty in representation in the SVG.
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