>>> [!note] Migrated issue <!-- Drupal.org comment --> <!-- Migrated from issue #1198924. --> Reported by: [catch](https://www.drupal.org/user/35733) >>> <p>People keep talking about performance between json and PHP but I haven't seen a single line of data actually posted.</p> <p>So time for some actual testing,</p> <p>The idea of this test is to simulate a full read of default module configuration - just reading the files into a PHP variable. We can assume that PHP variable would then need to be written somewhere but it's the same by the time it gets to that point.</p> <p>Here's what I did:</p> <p>Created a small (possibly too small) array.</p> <p>Wrote the same array out via drupal_var_export() to 500 php files, and via json_encode to 500 .json files. I've attached generate_json.php and generate_php.php and attached them there (as .txt files). You can stick these in your drupal 8 root and run them with drush scr - create the sites/default/config dir first.</p> <p>Then I made two scripts - read_json.php and read_php.php. The json version does $foo = json_encode(file_get_contents($foo)); the php version just includes the file.</p> <p>I then hit the files from a browser, once, profiling the whole thing with xhprof, with and without APC enabled. That adds up to three results sets instead of four, since JSON was within margin of error with and without APC -only relative percentages were different.</p> <p>Attaching 4 PHP scripts and a bunch of xhprof screenshots.</p> <p>Summary: </p> <p>For all three tests, total time spent was &lt; 20ms to read data from 500 files. Since these are defaults and supposed to be read very rarely this is negligible (json came out faster in wall time but it might be close to margin of error with APC enabled). This probably will matter if a level 2 store was reading from files, but I wasn't trying to simulate that.</p> <p>With the PHP version, peak memory was 1.6mb. Total memory used when running APC was just under 50% of the memory used by Drupal (2.8 out of 6mb).</p> <p>With the JSON version, peak memory was 100kb.</p> <p>Why is this?</p> <p>When you include a PHP file you can never free the memory up from including the actual file. Without APC it takes CPU + memory just to generate the opcode each time (this will also be true for an APC cache miss - which is likely to be the case with rarely-read defaults), additionally, things like function definitions and constants can never be freed up (not sure what overhead there is in APC when there are no functions, classes or constants but at least test case suggests there is something).</p> <p>With JSON, json_decode() uses some memory when it's working, but as soon as you leave function scope, that memory is freed up again.</p> <p>If you don't like my test write your own and post it here. This took much less than an hour to do, just running the same test yourself should be a few minutes at most using the files provided.</p> <p>I'm also uploading a screenshot of the apc.php per-directory cache report. This shows the 500 files in sites/default/config, and the fact they're taking up 2mb of memory in APC. You can see some Drupal core modules in the list - combined these files take up more than any individual module (it's actually about the same usage as about 8 medium-sized Drupal modules).</p> <p>Now if your level 2 store is also using PHP files for storage (which is the recommendation), you can double that to 1000 files in APC.</p> <p>Is 500 config files too much? Probably not. Let's say core as 50 modules, each with a config file each. Then 200 contrib modules - some like views are providing 20-30 files (one per default view or similar), some just provide 1. This can easily get to 500 - and most modules have many more than 4-5 variables, the actual files could be 5, 10, 20 times as large.</p> >>> [!note] Pre-migration files - [generate\_json.txt](https://www.drupal.org/files/issues/generate_json.txt) - [generate\_php.txt](https://www.drupal.org/files/issues/generate_php.txt) - [read\_json.txt](https://www.drupal.org/files/issues/read_json.txt) - [read\_php.txt](https://www.drupal.org/files/issues/read_php.txt) - [config\_json\_no\_apc.png](https://www.drupal.org/files/issues/config_json_no_apc.png) - [config\_php\_apc\_config\_files\_not\_cached.png](https://www.drupal.org/files/issues/config_php_apc_config_files_not_cached.png) - [config\_php\_in\_cache.png](https://www.drupal.org/files/issues/config_php_in_cache.png) - [config\_php\_no\_apc.png](https://www.drupal.org/files/issues/config_php_no_apc.png) >>>