Edit report at https://bugs.php.net/bug.php?id=78076&edit=1
ID: 78076
Updated by: cmb@php.net
Reported by: tyler dot bannister at remote-learner dot net
Summary: Opcache greatly increases memory usage.
-Status: Open
+Status: Feedback
Type: Bug
Package: opcache
Operating System: Centos 7.4.1708
PHP Version: 7.1.29
-Assigned To:
+Assigned To: cmb
Block user comment: N
Private report: N
New Comment:
PHP 7.1 receives only security fixes. Can you reproduce the issue
with any of the actively supported PHP versions[1].
[1] <https://www.php.net/supported-versions.php>
Previous Comments:
------------------------------------------------------------------------
[2019-05-27 21:28:19] tyler dot bannister at remote-learner dot net
Related To: Bug #76982
------------------------------------------------------------------------
[2019-05-27 21:25:07] tyler dot bannister at remote-learner dot net
Description:
------------
Using the database install script for Moodle 3.2, 3.3, 3.4, 3.5 or Totara 10, 11 or 12 with PHP
7.1.28 or 7.1.29 when opcache is turned on the script runs out of memory even if the memory limit is
increased to 2 GB, when opcache is turned off the script uses 78 MB of memory, when opcache is
turned on it ran out of memory with 2 GB of memory allowed, at 4 GB of memory the script was killed
before it could complete but it looked like it was using all of that memory before it was killed.
I suspect that issue is that during installation the Moodle install script does something incredibly
stupid, it turns off caching of language strings (it's multi-language system) which means every
time it needs to print a message it includes the file that contains the string. Over the course of
the database install it ends up including each file hundreds of times and with or without opcache
enabled each of those includes seems to increase the amount of memory used, but with opcache enabled
the memory usage grows much faster.
I've written a pair of simple test scripts to illustrate this behaviour.
Test script:
---------------
test1.php:
<?php
print("Starting Memory:". memory_get_usage() ."\n");
for ($x = 1; $x < 10000; $x += 1) {
include("test2.php");
}
print("Ending Memory:". memory_get_usage() ."\n");
test2.php:
<?php
$a = "Hello World!\n";
Expected result:
----------------
When test1.php and test2.php are placed in the same directory and the scrits are run with opcache
enabled and opcache disabled they should produce roughly the same starting and ending memory sizes.
Actual result:
--------------
Opcache disabled:
Starting Memory:349712
Ending Memory:349872
Opcache enabled:
Starting Memory:348856
Ending Memory:7820120
------------------------------------------------------------------------
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Edit this bug report at https://bugs.php.net/bug.php?id=78076&edit=1