Add perfetto tracing to host tooling#2502
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Example cvd create trace: https://ui.perfetto.dev/#!/?s=315a987bda469405966eb46797201e11b12d247c Example cvd fetch trace: https://ui.perfetto.dev/#!/?s=8e6e182ffab8e92f0f0a690b205c73313ec71f17 Perfetto uses a shared memory buffer between producer processes and the traced consumer daemon. `fork()` is problematic for this as the parent and child processes would end up clobbering each other when the shared memory buffer is inherited by the child. To prevent this, we introduce a perfetto wrapper that uses `pthread_atfork()` to register handlers that shutdown and restart tracing before and after forking. Perfetto also depends on global static data and explicitly calls out that it can not be restarted unless this data is cleared [1]. With this, the Perfetto wrapper utilizes `dlopen()` and `dlclose()` during init and shutdown. Perfetto also uses thread local data which requires extra care around `dlclose()` to prevent some thread local destructors from running after `dlclose()` has already unloaded the Perfetto library. To work around this, the Perfetto wrapper isolates all Perfetto calls into a single worker thread. [1] https://github.com/google/perfetto/blob/ab21398d658ce3bccc192b226d2731add6c02890/include/perfetto/tracing/tracing.h#L252 Bug: b/378560215
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Example cvd create trace:
https://ui.perfetto.dev/#!/?s=315a987bda469405966eb46797201e11b12d247c
Example cvd fetch trace:
https://ui.perfetto.dev/#!/?s=8e6e182ffab8e92f0f0a690b205c73313ec71f17