34 lines
1.7 KiB
Markdown
34 lines
1.7 KiB
Markdown
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# Introduction
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V8's CPU & Heap profilers are trivial to use from V8's shells (see V8Profiler), but it may appear confusing how to use them with Chromium. This page should help you with it.
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# Instructions
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## Why using V8's profilers with Chromium is different from using them with V8 shells?
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Chromium is a complex application, unlike V8 shells. Below is the list of Chromium features that affect profiler usage:
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* each renderer is a separate process (OK, not actually each, but let's omit this detail), so they can't share the same log file;
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* sandbox built around renderer process prevents it from writing to a disk;
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* Developer Tools configure profilers for their own purposes;
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* V8's logging code contains some optimizations to simplify logging state checks.
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## So, how to run Chromium to get a CPU profile?
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Here is how to run Chromium in order to get a CPU profile from the start of the process:
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```
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./Chromium --no-sandbox --js-flags="--logfile=%t.log --prof"
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```
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Please note that you wouldn't see profiles in Developer Tools, because all the data is being logged to a file, not to Developer Tools.
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### Flags description
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* **--no-sandbox** - turns off the renderer sandbox, obviously must have;
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* **--js-flags** - this is the containers for flags passed to V8:
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* **--logfile=%t.log** - specifies a name pattern for log files; **%t** gets expanded into current time in milliseconds, so each process gets its own log file; you can use prefixes and suffixes if you want, like this: **prefix-%t-suffix.log**;
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* **--prof** - tells V8 to write statistical profiling information into the log file.
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## Notes
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Under Windows, be sure to turn on .MAP file creation for **chrome.dll**, but not for **chrome.exe**.
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