![]() Which default, you ask? That would be opcache.jit=tracing. The JIT will use a default value if that property is omitted. Keep in mind that opcache.jit is optional by the way. So your ini settings (or -d flags) should have these values: opcache.enable=1 On Twitter or subscribe to my newsletter:Īnyways, internals propose 1255 as the best default, it will do maximum jitting, use the tracing JIT, use a global liner-scan register allocator - whatever that might be - and enables AVX instruction generation. If you want to stay up to date about what's happening on this blog, you can follow me Noticed a tpyo? You can submit a PR to fix it. Why there simply weren't four configuration entries added is beyond my comprehension, probably to make configuring the JIT faster… right? One small gotcha: the RFC lists these options in reverse order, so the first digit represents the C value, the second the R, and so on. Profile on the fly and compile hot functionsĬompile functions with tag in doc-comments Profile on first request and compile hot functions on second request Optimized JIT based on static type inference and inner procedure analyses Optimized JIT based on static type inference and call tree Optimized JIT based on static type inference of individual function The RFC lists the following options: # O - Optimization level 0 Mind you: this is not a bit mask, each number simply represents another configuration option. Now, what does that number mean? The RFC lists the meaning of each of them. It could look something like this: opcache.enable=1 All of these options are configured using a single (!) config entry: opcache.jit. You can configure when the JIT should run, how much it should try to optimise, etc. Next, there's several ways to configure the JIT (and this is where we'll get into the configuration mess). If enabled and on are true, you're good to go! The output should be something like this: array: 7 [ If you're actually running a CLI script, you'll need opcache.enable_cli.īefore continuing, let's ensure the JIT actually works, create a PHP script that's accessible via the browser or the CLI (depending on where you're testing the JIT), and look at the output of opcache_get_status(): var_dump( opcache_get_status()) ![]() The difference between opcache.enable and opcache.enable_cli is that the first one should be used if you're running, for example, the built-in PHP server. If you're testing the JIT in a CLI script, you'll need to use opcache.enable_cli instead to enable opcache: php -dopcache.enable_cli= 1 -dopcache.jit_buffer_size= 100M If this directive is excluded, the default value is set to 0, and the JIT won't run. Note that if you're running PHP via the commandline, you can also pass these options via the -d flag, instead of adding them to php.ini: php -dopcache.enable= 1 -dopcache.jit_buffer_size= 100M ![]() Enabling the JIT itself is done by specifying opcache.jit_buffer_size in php.ini. Still it's good to know about the JIT config in depth, so here goes.įirst of all, the JIT will only work if opcache is enabled, this is the default for most PHP installations, but you should make sure that opcache.enable is set to 1 in your php.ini file. Luckily there are some configuration shorthands available so that it's more easy to set up. Honestly, setting up the JIT is one of the most confusing ways of configuring a PHP extension I've ever seen. ![]()
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