![]() ![]() 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. So, how does OPcache make PHP faster? And what changes in the execution process with JIT? The following image shows a visual representation of the basic PHP execution process. Interpretation: Opcodes are interpreted and run on the Zend VM.Compilation: The interpreter traverses the tree and translates AST nodes into low-level Zend opcodes, which are numeric identifiers determining the type of instruction performed by the Zend VM.Parsing: The interpreter checks if the script matches the syntax rules and uses tokens to build an Abstract Syntax Tree (AST), a hierarchical representation of the structure of source code.Lexing/Tokenizing: First, the interpreter reads the PHP code and builds a set of tokens.To better understand what JIT is for PHP, let’s take a quick look at how PHP executes the source code to the final result. ![]() So, how did we get to JIT, and what is the difference between JIT vs OPcache? When enabled, native code of PHP files is stored in an additional region of the OPcache shared memory and op_array→opcodes.handler(s) keep pointers to the entry points of JIT-ed code.” It may be enabled/disabled at PHP compile time and at run-time. “PHP JIT is implemented as an almost independent part of OPcache. The RFC proposal describes JIT as follows: The most acclaimed feature coming with PHP 8 is the Just-in-time (JIT) compiler. ![]()
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