a2af7e1101
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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| benchmarks | ||
| build_overrides | ||
| custom_deps | ||
| docs | ||
| gni | ||
| include | ||
| infra | ||
| samples | ||
| src | ||
| test | ||
| testing | ||
| third_party | ||
| tools | ||
| .clang-format | ||
| .clang-tidy | ||
| .editorconfig | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitignore | ||
| .gn | ||
| .vpython | ||
| .ycm_extra_conf.py | ||
| AUTHORS | ||
| BUILD.gn | ||
| ChangeLog | ||
| CODE_OF_CONDUCT.md | ||
| codereview.settings | ||
| DEPS | ||
| LICENSE | ||
| LICENSE.fdlibm | ||
| LICENSE.strongtalk | ||
| LICENSE.v8 | ||
| LICENSE.valgrind | ||
| OWNERS | ||
| PRESUBMIT.py | ||
| README.md | ||
| snapshot_toolchain.gni | ||
| WATCHLISTS | ||
V8 JavaScript Engine
V8 is Google's open source JavaScript engine.
V8 implements ECMAScript as specified in ECMA-262.
V8 is written in C++ and is used in Google Chrome, the open source browser from Google.
V8 can run standalone, or can be embedded into any C++ application.
V8 Project page: https://v8.dev/docs
Getting the Code
Checkout depot tools, and run
fetch v8
This will checkout V8 into the directory v8 and fetch all of its dependencies.
To stay up to date, run
git pull origin
gclient sync
For fetching all branches, add the following into your remote
configuration in .git/config:
fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
fetch = +refs/tags/*:refs/tags/*
Contributing
Please follow the instructions mentioned at v8.dev/docs/contribute.