[CentOS] Memory Leak with PHP

I understand that this problem may have very little to do with CentOs, but it happens to occur on a CentOS webserver and maybe you’ll have a clue.

Since a few months, after many upgrades on several blogs (now running with PHP7), our server is eating up RAM no end. PHP processes swell to over 2 GB (each) and when the whole RAM and the whole swap are full, problems stack up and finally paralyze the system. This despite having “memory_limit = 512M" in all php.ini (there are several PHP versions on the system, selection is made via .htaccess).

CenOS 6.9 on a Xeon 8 cores with now 64 GB RAM.
This is a snip of a top this morning, just 2 days after the latest reboot:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND

31163 apache    20   0  939m 690m 8876 S 51.5  1.1 102:16.90 php-fpm

29603 apache    20   0 1208m 961m  10m S 33.7  1.5 136:54.95 php-fpm

11858 apache    20   0 1660m 1.4g 9564 R 31.3  2.2 190:41.25 php-fpm

31207 apache    20   0  916m 668m 9636 R 18.1  1.0 101:38.72 php-fpm

31218 apache    20   0  930m 682m 9264 S 16.8  1.1 101:55.51 php-fpm

2873 apache    20   0 1694m 1.4g 9972 S 11.2  2.2 194:42.82 php-fpm

2854 apache    20   0 1657m 1.4g  10m S  9.9  2.2 191:15.43 php-fpm

2326 mysql     20   0 4993m 1.3g 6076 S  7.3  2.0 149:11.06 mysqld

2842 apache    20   0 1664m 1.4g 8996 S  4.9  2.2 191:34.00 php-fpm

17085 apache    20   0 1454m 1.2g 9824 S  1.3  1.9 167:25.43 php-fpm

13850 apache    20   0  464m  45m 5872 S  1.0  0.1   0:43.55 httpd

20044 root      20   0 15276 1496  952 R  1.0  0.0  15:05.99 top

1936 apache    20   0 1684m 1.4g  10m S  0.7  2.2 192:37.37 php-fpm

19109 apache    20   0  463m  44m 5808 S  0.7  0.1   0:18.66 httpd

24782 apache    20   0  465m  46m 5720 S  0.7  0.1   0:12.01 httpd

1848 apache    20   0 1579m 1.3g  10m S  0.3  2.1 183:02.13 php-fpm

2718 root      20   0 1074m  12m 2536 S  0.3  0.0   7:32.85 fail2ban-server

15221 apache    20   0  475m  49m 9508 S  0.3  0.1   0:22.24 httpd

16764 apache    20   0  476m  49m 9456 S  0.3  0.1   0:21.82 httpd

17757 apache    20   0  461m  42m 5784 S  0.3  0.1   0:18.26 httpd

19108 apache    20   0  463m  44m 5848 S  0.3  0.1   0:20.80 httpd

19155 apache    20   0  463m  44m 5756 S  0.3  0.1   0:17.15 httpd

24791 apache    20   0  462m  43m 5764 S  0.3  0.1   0:14.87 httpd

24794 apache    20   0  464m  45m 5780 S  0.3  0.1   0:15.07 httpd

29668 apache    20   0  459m  40m 5888 S  0.3  0.1   0:34.05 httpd

29794 apache    20   0  463m  44m 5868 S  0.3  0.1   0:35.23 httpd

31184 apache    20   0  936m 688m 9572 S  0.3  1.1 103:33.80 php-fpm

31212 apache    20   0  908m 660m 9860 S  0.3  1.0 101:27.74 php-fpm

Any idea, suggestion would be greatly appreciated! --