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Benedikt Meurer authored
This adds OBJECT/SNAPSHOT trace events for Script and SharedFunctionInfo objects, logging their creation with appropriate information to make sense of them. Based on that we introduces five flow events to model the optimized compilation via tracing in the "disabled-by-default-v8.compile" category: - "v8.optimizingCompile.start" logs the creation of the PipelineCompilationJob (for TurboFan JavaScript optimization) with the "function" argument referring to the trace event object created for the SharedFunctionInfo. - "v8.optimzingCompile.prepare" logs the preparation of the PipelineCompilationJob on the main thread, also carrying the "function" argument. This connects the flow event to the actual tracing duration event associated with the preparation phases. - "v8.optimizingCompile.execute" logs the (usually concurrent) optimization of the TurboFan graph (again with "function"). - "v8.optimizingCompile.finalize" logs the main thread phase which finalizes the optimized code and eventually installs it (in case of success). - "v8.optimizingCompile.end" signals the end of the PipelineCompilationJob, which carries the "compilationInfo", that contains the interesting bits of the OptimizedCompilationInfo, specifically whether the compile was successfull and which functions were inlined for example. This also adds two instant events "V8.AbortOptimization" and "V8.RetryOptimization" in "disabled-by-default-v8.compile" category that are emitted when TurboFan cannot optimize a certain function. In case of "V8.RetryOptimization", TurboFan might be able to optimize it later, whereas "V8.AbortOptimization" permanently disables the optimization of a given function. The JSON representation of this is ```js { "pid": 256639, "tid": 256639, "ts": 6935411377801, "tts": 159116, "ph": "I", "cat": "disabled-by-default-v8.compile", "name": "V8.AbortOptimization", "dur": 0, "tdur": 0, "args": { "reason": "Function is too big to be optimized", "function": { "id_ref": "0x600000001", "scope": "v8::internal::SharedFunctionInfo" } } }, ``` where the "function" refers to a previously emitted SNAPSHOT for the function in question. In the trace viewer it will show up as instant event under "v8.optimizingCompile.prepare" in case of the relevant example where optimization is disabled due to reaching the bytecode limit (as in the JSON above), i.e. it'll look something like this https://i.paste.pics/aafc2de9df10ea8f5acc1a761d80f07b.png for the example highlighted in the recent blog post https://ponyfoo.com/articles/javascript-performance-pitfalls-v8 that describes the optimization limit. The "v8.optimizingCompile.end" duration event will also carry this information as part of the "compilationInfo" object, but specifically for CI tools, etc. it might be a whole lot easier to just look for the "V8.AbortOptimization" instant event. Bug: v8:8598, v8:9039 Tbr: ulan@chromium.org Doc: bit.ly/v8-tracing-signals Change-Id: Ic87ac336004690c65b6b15ad73bc6fbd4b5f12c4 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1511483 Commit-Queue: Benedikt Meurer <bmeurer@chromium.org> Reviewed-by: Peter Marshall <petermarshall@chromium.org> Reviewed-by: Benedikt Meurer <bmeurer@chromium.org> Cr-Commit-Position: refs/heads/master@{#60448}
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