forked from https://github.com/symfony/symfony
cd5c1d6361
This PR was merged into the 5.1-dev branch.
Discussion
----------
[YAML] Improve performance of YAML parser
| Q | A
| ------------- | ---
| Branch? | master
| Bug fix? | no
| New feature? | no
| Deprecations? | no
| License | MIT
Optimise various methods and conditions to use best
performing alternatives where possible. Roughly:
* Uses methods that do not copy memory, e.g. strncmp
as alternative for strpos matching beginning of string.
* Switches order of some conditions to put the cheapest
checks first in order.
* Checks input before calling trim() - despite the function
returning the same string as input, it still costs memory
and introduces unnecessary overhead.
* Extracts variables for repeated identical function calls.
* Uses negative substring offsets instead of strlen + substr.
* Replaces single-char substr usages with substring access.
Profiling method
-----------------
Profiled using a custom script which splits and parses all provided `fixture` files from the YAML component's test directory, then profiled this through Blackfire and identified frequent method calls.
Refactoring strategy
--------------------
Most important change: switching strpos to strncmp to avoid scanning a full (and potentially very long) YAML line for occurrence of a substring.
Whenever possible, I've gone for PHP methods that do not copy memory and replaced some instances of function calls which could be replaced with substring access.
In methods which are called frequently I've gone for guard clauses to prevent further processing if a YAML line is, for example, empty. Such as avoiding trim() on already empty lines.
Profiling results
----------------
A Blackfire profiling delta can be seen on https://blackfire.io/profiles/compare/90fd3005-8b9f-4534-8bd8-1e66832bf247/graph. Taken with 200 samples which render every YAML fixture from the component's test dir.
Commits
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| .github | ||
| src/Symfony | ||
| .appveyor.yml | ||
| .editorconfig | ||
| .gitignore | ||
| .php_cs.dist | ||
| .travis.yml | ||
| CHANGELOG-4.0.md | ||
| CHANGELOG-4.1.md | ||
| CHANGELOG-4.2.md | ||
| CHANGELOG-4.3.md | ||
| CHANGELOG-4.4.md | ||
| CHANGELOG-5.0.md | ||
| CODE_OF_CONDUCT.md | ||
| composer.json | ||
| CONTRIBUTING.md | ||
| CONTRIBUTORS.md | ||
| LICENSE | ||
| link | ||
| phpunit | ||
| phpunit.xml.dist | ||
| README.md | ||
| UPGRADE-4.0.md | ||
| UPGRADE-4.1.md | ||
| UPGRADE-4.2.md | ||
| UPGRADE-4.3.md | ||
| UPGRADE-4.4.md | ||
| UPGRADE-5.0.md | ||
| UPGRADE-5.1.md | ||
| UPGRADE-6.0.md | ||
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