PHP Warning: Unknown: Unable to allocate memory for pool. in Unknown on line 0

It was shiny morning and at the time of taking tea at home. I opened my laptop and login into my server. Recently, I changed the apache MPM to worker mode. Running php-fpm and mod_fcgi to run the WordPress based blog.

After a few days of Worker apache implementation, I checked the php-fpm log directory and found some error that is

[root@mysites php-fpm]# tail www-error.log
[26-Jun-2014 13:39:34] PHP Warning: Unknown: Unable to allocate memory for pool. in Unknown on line 0
[26-Jun-2014 13:48:00] PHP Warning: Unknown: Unable to allocate memory for pool. in Unknown on line 0

To solve this issue, I optimize the php apc.

In CentOS/Red Hat and Scientific Linux, the absoute path of apc.php is /etc/php.d/apc.php

I optimizes mainly these 4 values –

apc.shm_size
apc.num_files_hint
apc.user_entries_hint
apc.ttl

Optimizing the PHP apc takes time, I need some monitoring and playing around with these above 4 values.

I am sharing my apc.ini file which is working for me.
Note: Detailed description on below given egrep command

[root@mysites php.d]# egrep -v '^;|^$' apc.ini
extension = apc.so
apc.enabled=1
apc.shm_segments=1
apc.shm_size=128M
apc.num_files_hint=20000
apc.user_entries_hint=20000
apc.ttl=7200
apc.use_request_time=1
apc.user_ttl=7200
apc.gc_ttl=3600
apc.cache_by_default=1
apc.filters
apc.mmap_file_mask=/tmp/apc.XXXXXX
apc.file_update_protection=2
apc.enable_cli=0
apc.max_file_size=20M
apc.stat=1
apc.stat_ctime=0
apc.canonicalize=0
apc.write_lock=1
apc.report_autofilter=0
apc.rfc1867=0
apc.rfc1867_prefix =upload_
apc.rfc1867_name=APC_UPLOAD_PROGRESS
apc.rfc1867_freq=0
apc.rfc1867_ttl=3600
apc.include_once_override=0
apc.lazy_classes=0
apc.lazy_functions=0
apc.coredump_unmap=0
apc.file_md5=0
apc.preload_path
[root@mysites php.d]# 

Restart the apache and php-fpm

service httpd restart

service php-fpm restart

Visual Dashboard of PHP APC status

The PHP apc comes with awesome dashboard.

Copy apc.php file into DocumentRoot of your website. Replace /var/www/html/website-name with your website DocumentRoot

cp /usr/share/php-pecl-apc/apc.php /var/www/html/website-name

Change the password of apc dashboard.
Here default username s apc.

Find the below given line in apc.php file which you have copied into website DocumentRoot. Change the password.

defaults('ADMIN_USERNAME','apc');                       // Admin Username
defaults('ADMIN_PASSWORD','password');          // Admin Password - CHANGE THIS TO ENABLE!!!

Restart Apache and php-fpm once again

service httpd restart
service php-fpm restart

The below given is the reference from my live server. Still I am monitoring and optimizing the PHP APC. Right now error is gone and I marked it as solved.

PHP APC Documentation