“The benefits of the JIT compiler are roughly (and as already outlined in the RFC): Nevertheless, JIT could bring several benefits for developers. So, we shouldn’t expect a significant boost in PHP execution speed when it comes to WordPress and similar apps. Relative JIT contribution to PHP 8 performance (Image source: PHP 8.0 Announcement Addendum) Web apps like WordPress also rely on other factors like TTFB, database optimization, HTTP requests, etc. With JIT enabled, the code wouldn’t be run by the Zend VM, but by the CPU itself, which would improve the calculation speed. It’s planned to provide additional effort, improving JIT for real-life apps, using profiling and speculative optimizations.” “… like the previous attempts – it currently doesn’t seem to significantly improve real-life apps like WordPress (with opcache.jit=1235 326 req/sec vs 315 req/sec). The early tests show that JIT would make CPU-intensive workloads run significantly faster. But would we really experience such improvements in real-life apps like WordPress? Zeev Surasky, co-author of the PHP JIT proposal, shows how much calculations would be faster with JIT:īut, would JIT effectively improve WordPress performance? JIT for Live Web AppsĪccording to the JIT RFC, the just in time compiler implementation should improve PHP performance. Bypassing compilation, it’d be able to bring considerable improvements in performance and memory usage. In short, JIT translates the hot parts of the intermediate code into machine code. JIT “doesn’t introduce any additional IR (Intermediate Representation) form,” but uses DynASM (Dynamic Assembler for code generation engines) to generate native code directly from PHP byte-code. JIT - The Just in Time CompilerĮven if opcodes are low-level intermediate representation, they still have to be compiled into machine code. You can read more about preloading in our introduction to PHP 7.4. Preloading provides a way to store a specified set of scripts into OPcache memory “ before any application code is run.” Still, it doesn’t bring tangible performance improvement for typical web-based applications. OPcache has been recently improved with the implementation of preloading, a new OPcache feature added with PHP 7.4. Zend OPcache section in a phpinfo page Preloading Suggested reading: How to Improve PHP Memory Limit in WordPress. PHP execution process with OPcache enabledĪs of PHP 5.5, the Zend OPcache extension is available by default, and you can check if you have it correctly configured by simply calling phpinfo() from a script on your server or checking out your php.ini file (see OPcache configuration settings). Since PHP bytecodes are stored in shared memory, they are immediately available as low-level intermediate representation and can be executed on the Zend VM right away. With OPcache enabled, the PHP interpreter goes through the 4 stage process mentioned above only when the script runs for the first time. “OPcache improves PHP performance by storing precompiled script bytecode in shared memory, thereby removing the need for PHP to load and parse scripts on each request.” This is where the OPcache extension comes in to play: This may result in wasting CPU resources and additional time. This means, when a PHP script runs, the interpreter parses, compiles, and executes the code over and over again on each request.
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