Bug #78076 [Com]: Opcache greatly increases memory usage.

Edit report at https://bugs.php.net/bug.php?id=78076&edit=1 ID: 78076 Comment by: turchanov at farpost dot com Reported by: tyler dot bannister at remote-learner dot net Summary: Opcache greatly increases memory usage. Status: Verified Type: Bug Package: opcache Operating System: Centos 7.4.1708 PHP Version: 7.2.18 Assigned To: dmitry Block user comment: N Private report: N New Comment: Are there any plans to fix this? This bug effectively prevents us from using OPCache in "cli" mode. Using file_cache_only=1 seems very logical/practical for cli mode. And we hit memory_limit due to this bug. An alternative - 'file_cache_only=0', means that every running cli php will have its own private SHM cache of 200M (yes, we cache a lot!). This incurs a HUGE memory waste. Previous Comments: ------------------------------------------------------------------------ [2020-03-31 08:22:23] dmitry@php.net Unfortunately the fix proposed at https://github.com/php/php-src/pull/5321 is incorrect. It causes use-after-free and following crash. Opcache in file_cache_only mode uses CG(arena) to store data loaded from file cache by the end of request. This is done by design, because all the functions and classes loaded from file cache are kept by the end of request anyway. The only part that is not necessary after the include() finishes - main op_array. In general, it should be possible to detect if file_cache contains only main op_array, then copy all relevant parts to emalloc()-ed process memory and then deallocate buffer. However, this is not an easy fix. ------------------------------------------------------------------------ [2020-03-29 22:18:49] thedinosaurmail at gmail dot com The following pull request has been associated: Patch Name: fix bug 78076 On GitHub: https://github.com/php/php-src/pull/5321 Patch: https://github.com/php/php-src/pull/5321.patch ------------------------------------------------------------------------ [2020-02-18 14:58:20] cmb@php.net I can confirm the reported behavior (PHP 7.3 and 7.4 on Windows 10). ------------------------------------------------------------------------ [2019-05-28 16:06:47] tyler dot bannister at remote-learner dot net I've continued testing the problem, and on the command line I was able to stop the memory explosion in my test script by setting opcache.file_cache_only=0. However, I only enabled that setting in the first place to deal with the problem of running out of memory with the Moodle installer. So the issue isn't exclusive to having file_cache_only enabled, but maybe that setting makes the problem worse? The minimal number of non-default settings to replicate (on my now Centos 7.6.1810 with PHP 7.3.5 system) seems to be: opcache.enable=1 opcache.enable_cli=1 opcache.file_cache="/var/lib/php/cli-opcache" opcache.file_cache_only=1 I was also able to replicate the problem on Ubuntu 18.04.2 with PHP 7.2.17: Opcache enabled with opcache.file_cache_only enabled: Starting Memory:389008 Ending Memory:7860232 Opcache enabled with opcache.file_cache_only disabled: Starting Memory:388432 Ending Memory:388432 Opcache disabled: Starting Memory:389992 Ending Memory:390144 ------------------------------------------------------------------------ [2019-05-28 15:43:12] tyler dot bannister at remote-learner dot net PHP 7.28 actual output: Opcache enabled: Starting Memory:385248 Ending Memory:7856480 Opcache disabled: Starting Memory:386104 Ending Memory:386232 PHP 7.3.5 actual output: Opcache enabled: Starting Memory:389112 Ending Memory:8450224 Opcache disabled: Starting Memory:389904 Ending Memory:390088 ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=78076 -- Edit this bug report at https://bugs.php.net/bug.php?id=78076&edit=1