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vperfetto

vperfetto is a way to make it easier to process perfetto traces in the virtual machine use case. It consists of an online component where the user can set up guest host communication and send messages to the host and call into the vperfetto library to mark guest time and start/end of tracing, and an offline component to merge guest/host traces after the fact.

Dependencies

You'll need libprotoc, libprotobuf and the protoc compiler available so that CMake's FindProtobuf succeeds. There is an ExternalProject_Add routine in protobuf.cmake but it needs to do its work at configure, not build time.

Build

# protobuf is required. On debian buster, do this to install it.
# sudo apt-get install libprotoc-dev protobuf-compiler

mkdir build
cd build
cmake . ../
make

generates libvperfetto.so for online and vperfetto_merge for offline usage.

How to use

Online using guest-triggered tracing

Link libvperfetto.so

Workflow (namespace vperfetto)

vperfetto workflow

Offline using separate guest/host traces

This is useful if you've generated traces already but just want to merge them. The binary takes 3 mandatory arguments for the guest/host trace and another argument for the combined output trace file. There is one optional argument to specify the CLOCK_BOOTTIME in the guest (in nanoseconds) when the host trace started to help line things up:

./vperfetto_merge <guest.trace> <host.trace> <combined.trace(forWriting)> [guestTraceStartTimeNs]

Min option

If you only need track events and counters, set OPTION_USE_PERFETTO_SDK to FALSE in CMakeLists.txt; resulting binary is smaller.

Known issues

Trace counters not yet supported in the SDK variant. vperfetto_merge must be built with OPTION_USE_PERFETTO_SDK TRUE or it is useless.

Library structure

perfetto-min/ contains perfetto base libraries, protozero, and protobuf definitions. It's used to generate the non-SDK variant (OPTION_USE_PERFETTO_SDK=FALSE).

proto/ is for the SDK variant (OPTION_USE_PERFETTO_SDK=TRUE) and contains the full perfetto_trace.proto.

perfetto.cc/perfetto.h is the v7 perfetto sdk, except also exporting a function to generate UUID lsbs for easier renaming of uuids in trace processing.

vperfetto.h is the interface to this library.

vperfetto-sdk.cpp is the perfetto SDK-based implementation of the interface (OPTION_USE_PERFETTO_SDK=TRUE). vperfetto.cpp is the non-SDK implementation of the interface (OPTION_USE_PERFETTO_SDK=FALSE).

vperfetto_unittest.cpp contains tests. TODO: Add more