Use faster hash algorithm (xxh128) on PHP 8.1+ #3588
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This breaks a test assertion |
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stof
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Nov 8, 2021
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GromNaN
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Nov 23, 2021
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Having a different cache in function of the PHP version might be an issue if the cache is pregenerated in a different environment and packaged with the application. Cache key change with PHP version.
We can remove calls to the hash function is some places to get better performance improvements without cache variation. See #3601
| @@ -350,7 +350,7 @@ public function getTemplateClass($name, $index = null) | |||
| { | |||
| $key = $this->getLoader()->getCacheKey($name).$this->optionsHash; | |||
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| return $this->templateClassPrefix.hash('sha256', $key).(null === $index ? '' : '___'.$index); | |||
| return $this->templateClassPrefix.hash(\PHP_VERSION_ID < 80100 ? 'sha256' : 'xxh128', $key).(null === $index ? '' : '___'.$index); | |||
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The class name is hashed twice at runtime, for every template load. Once in FilesystemCache::generateKey and the second here.
This was referenced Dec 13, 2021
fabpot
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Dec 14, 2021
…s during compilation (GromNaN) This PR was squashed before being merged into the 2.x branch. Discussion ---------- Hashing is not necessary to generate unique variable names during compilation Trying to optimize calls to `hash` function (#3588), I found that some calls are made during compilation that are not necessary at all. According to the last commits on this functions (57ff882 & 6ab5fe9), the internal variable names must be unique and deterministic. Using a simple sequence is enough. This avoid CPU cycles during compilation. Which should not have any impact on production; but still interesting for dev&test. Commits ------- ba2b4e6 Hashing is not necessary to generate unique variable names during compilation
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@GromNaN Can you rebase this PR? |
stof
approved these changes
Dec 15, 2021
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Thank you @GromNaN. |
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Twig uses the
hashfunction at runtime to convert template paths class names, each time a template is loaded. In a large project with a high granularity of templates (hundreds ofincludeper page), this can become the most time consuming function as reported by Blackfire:To optimise this use-case, PHP 8.1 supports the xxHash hash algorithms.
xxh128is 60x faster thatsha256according to the benchmarks, and guarantee a very low risk of collision.I'm not able to test with PHP 8.1 for now. Before going further I would like to validate performance impact on a large list of file names.