Bug #74250 [Asn->Csd]: OPcache compilation performance regression in PHP 5.6/7 with huge classes

Edit report at https://bugs.php.net/bug.php?id=74250&edit=1 ID: 74250 Updated by: nikic@php.net Reported by: dzuelke at gmail dot com Summary: OPcache compilation performance regression in PHP 5.6/7 with huge classes -Status: Assigned +Status: Closed Type: Bug Package: opcache Operating System: Linux PHP Version: 7.0.16 Assigned To: nikic Block user comment: N Private report: N New Comment: Relevant commits for the DFA pass: Call lookup: https://github.com/php/php-src/commit/9331be7d6af4ba9ab9945ac1d72812603fdd821c Loop identification / DJ spanning tree: https://github.com/php/php-src/commit/6633e8492e6195c4085b04c65fb18addd0ac33a6 https://github.com/php/php-src/commit/f1f68b60f5e6f75002560b44211f3449b25f918d Worklist management: https://github.com/php/php-src/commit/e60515f3b84b9d24748cdd7aa9ccbfa3cfa23d62 https://github.com/php/php-src/commit/052aa466e1f309c83503fede7f02ffa4ed772d4a Resolving the performance problems in the block pass would require some larger changes. Instead I disabled it entirely for large functions (the sample file is 20x over the threshold): https://github.com/php/php-src/commit/7ea261685f179a7cddcc4196fc7f3f12572c3d49 Previous Comments: ------------------------------------------------------------------------ [2017-03-15 09:36:18] dzuelke at gmail dot com Description: ------------ There appears to be a performance regression in the CFG and DFA based optimization passes of OPcache in PHP 5.6+ when loading huge classes (such as those generated by Symfony's routing component) for the first time. The issue does not occur on PHP 5.5. Tests below are with 5.6.30, 7.0.16 and 7.1.2 and default INI settings; I replicated the issue on both macOS and Linux. Test file here (it's from an actual application, slightly anonymized, not a synthetic example): https://gist.github.com/dzuelke/fe867f55f09e0bf79ecefcc815b7fe92 Without OPcache, everything is fine in all versions: $ time -p php -dopcache.enable_cli=0 hugeclass.php real 0.10 user 0.09 sys 0.00 With OPcache on, things are suddenly much, much slower: 5.6: $ time -p php -dopcache.enable_cli=1 hugeclass.php real 3.23 user 3.21 sys 0.02 7.0: $ time -p php -dopcache.enable_cli=1 hugeclass.php real 1.76 user 1.73 sys 0.02 7.1: $ time -p php -dopcache.enable_cli=1 hugeclass.php real 4.01 user 3.98 sys 0.02 For comparison, 5.5 is as speedy as you'd expect it to be: $ time -p php -dopcache.enable_cli=1 hugeclass.php real 0.14 user 0.11 sys 0.02 If we switch off optimization passes 5 (CFG based) and 6 (DFA based, only in 7.1), everything is great again in all versions: $ time -p php -dopcache.enable_cli=1 -dopcache.optimization_level=0x7FFFFFCF hugeclass.php real 0.13 user 0.10 sys 0.02 For 5.6 and 7.0, pass 6 is not a thing, but in 7.1, we can inspect passes 5 and 6 separately. Pass 5 (CFG based) already makes for a drastic performance hit in 7.1: $ time -p php -dopcache.enable_cli=1 -dopcache.optimization_level=0x7FFFFFDF hugeclass.php real 0.88 user 0.86 sys 0.01 But pass 6 (DFA based) is the one that causes the biggest slowdown in 7.1: $ time -p php -dopcache.enable_cli=1 -dopcache.optimization_level=0x7FFFFFEF hugeclass.php real 3.29 user 3.24 sys 0.04 In all versions, subsequent loads from the cache (such as when running FPM or the built-in web server) are fast. Confirmed as bug in both CFG and DFA passes by Nikita: http://news.php.net/php.internals/98518 Test script: --------------- https://gist.github.com/dzuelke/fe867f55f09e0bf79ecefcc815b7fe92 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=74250&edit=1