76 lines
3.5 KiB
Markdown
76 lines
3.5 KiB
Markdown
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# What is this
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Contains a written down set of principles and other information on //base.
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Please add to it!
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## About //base:
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Chromium is a very mature project. Most things that are generally useful are
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already here and things not here aren't generally useful.
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Base is pulled into many projects. For example, various ChromeOS daemons. So
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the bar for adding stuff is that it must have demonstrated wide
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applicability. Prefer to add things closer to where they're used (i.e. "not
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base"), and pull into base only when needed. In a project our size,
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sometimes even duplication is OK and inevitable.
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Adding a new logging macro `DPVELOG_NE` is not more clear than just
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writing the stuff you want to log in a regular logging statement, even
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if it makes your calling code longer. Just add it to your own code.
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If the code in question does not need to be used inside base, but will have
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multiple consumers across the codebase, consider placing it in a new directory
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under components/ instead.
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## Qualifications for being in //base OWNERS
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* interest and ability to learn low level/high detail/complex c++ stuff
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* inclination to always ask why and understand everything (including external
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interactions like win32) rather than just hoping the author did it right
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* mentorship/experience
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* demonstrated good judgement (esp with regards to public APIs) over a length
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of time
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Owners are added when a contributor has shown the above qualifications and
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when they express interest. There isn't an upper bound on the number of OWNERS.
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## Design and naming
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* Be sure to use the base namespace.
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* STL-like constructs should adhere as closely to STL as possible. Functions
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and behaviors not present in STL should only be added when they are related
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to the specific data structure implemented by the container.
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* For STL-like constructs our policy is that they should use STL-like naming
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even when it may conflict with the style guide. So functions and class names
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should be lower case with underscores. Non-STL-like classes and functions
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should use Google naming.
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## Performance testing
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Since the primitives provided by //base are used very widely, it is important to
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ensure they scale to the necessary workloads and perform well under all
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supported platforms. The `base_perftests` target is a suite of
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synthetic microbenchmarks that measure performance in various scenarios:
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* BasicPostTaskPerfTest: Exercises MessageLoopTaskRunner's multi-threaded
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queue in isolation.
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* ConditionVariablePerfTest: Measures thread switching cost of condition
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variables.
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* IntegratedPostTaskPerfTest: Exercises the full MessageLoop/RunLoop
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machinery.
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* JSONPerfTest: Tests JSONWriter and JSONReader performance.
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* MessageLoopPerfTest: Measures the speed of task posting in various
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configurations.
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* ObserverListPerfTest: Exercises adding, removing and signalling observers.
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* PthreadEventPerfTest: Establishes the baseline thread switching cost using
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pthreads.
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* ScheduleWorkTest: Measures the overhead of MessagePump::ScheduleWork.
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* SequenceManagerPerfTest: Benchmarks SequenceManager scheduling with various
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underlying task runners.
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* TaskObserverPerfTest: Measures the incremental cost of adding task
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observers.
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* TaskPerfTest: Checks the cost of posting tasks between threads.
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* WaitableEvent{Thread,}PerfTest: Measures waitable events in single and
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multithreaded scenarios.
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Regressions in these benchmarks can generally by caused by 1) operating system
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changes, 2) compiler version or flag changes or 3) changes in //base code
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itself.
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