What is causing Unable to allocate memory for pool in PHP

Question

I ve occasionally run up against a server s memory allocation limit  particularly with a bloated application like Wordpress  but never encountered  Unable to allocate memory for pool  and having trouble tracking down any information   Does anyone know what this means   I ve tried increasing the memory limit without success   I also haven t made any significant changes to the application  One day there was no problem  the next day I hit this error

User · Answer

This worked for our guys  running a slew of Wordpress sites on the same server     Changed memory settings in the  etc php d apc ini file  It was set to 64M  so we doubled it to 128M   apc shm size 128M

User · Answer

solution for me    apc ttl 0  apc shm size anything you want   edit start  warning    bokan indicated me that i should add a warning here    if you have a ttl of 0 this means the every cached item can be purged immediately  so if you have a small cache size like 2mb and a ttl of 0 this would render the apc useless  because the data in the cache gets always overwritten   lowering the ttl means only that the cache cannot become full  only with items which can t be replaced   so you have to choose a good balance between ttl and cache size   in my case i had a cache size of 1gb  so it was more than enough for me   edit end  had the same issue on centos 5 with php 5 2 17 and noticed that if the cache size is small and the ttl parameter is  high   like 7200  while having a lot of php files to cache  then the cache fills up quite fast and apc doesn t find anything which it can remove because all files in the cache still fit in the ttl   increasing the memory size is only a part solution  you still run in this error if you cache fills up and all files are within the ttl   so my solution was to set the ttl to 0  so apc fills up the cache an there is allways the possibility for apc to clear some memory for new data   hope that helps  edit  see also  http   pecl php net bugs bug php id 16966  download http   pecl php net get APC extract and run the apc php  there you have a nice diagram how your cache usage look like

User · Answer

Monitor your Cached Files Size  you can use apc php from apc pecl package  and increase apc shm size according to your needs   This solves the problem

User · Answer

Probably is APC related   For the people having this problem  please specify you  ini  settings  Specifically your apc mmap file mask setting   For file-backed mmap  it should be set to something like   apc mmap file mask  tmp apc XXXXXX   To mmap directly from  dev zero  use   apc mmap file mask  dev zero   For POSIX-compliant shared-memory-backed mmap  use   apc mmap file mask  apc shm XXXXXX

User · Answer

Looking at the internets there can be various of causes  In my case leaving everything default except     apc shm size   64M      cleared the countless warnings that I was getting earlier

User · Answer

on my system i had to insert apc shm size   64M into  usr local etc php ini  FreeBSD 9 1  then when i looked at apc php  which i copied from  usr local share doc APC apc php to  usr local www apache24 data  i found that the cache size had increased from the default of 32M to 64M and i was no longer getting a large cache full count  references  http   au1 php net manual en apc configuration php also read Bokan s comments  they were very helpful

User · Answer

Using a TTL of 0 means that APC will flush all the cache when it runs out of memory  The error don t appear anymore but it makes APC far less efficient  It s a no risk  no trouble   I don t want to do my job  decision  APC is not meant to be used that way  You should choose a TTL high enough so the most accessed pages won t expire  The best is to give enough memory so APC doesn t need to flush cache   Just read the manual to understand how ttl is used   http   www php net manual en apc configuration php ini apc ttl  The solution is to increase memory allocated to APC  Do this by increasing apc shm size   If APC is compiled to use Shared Segment Memory you will be limited by your operating system  Type this command to see your system limit for each segment    sysctl -a   grep -E  shmall shmmax    To alocate more memory you ll have to increase the number of segments with the parameter apc shm segments   If APC is using mmap memory then you have no limit  The amount of memory is still defined by the same option apc shm size    If there s not enough memory on the server  then use filters option to prevent less frequently accessed php files from being cached   But never use a TTL of 0   As c33s said  use apc php to check your config  Copy the file from apc package to a webfolder and point browser to it  You ll see what is really allocated and how it is used  The graphs must remain stable after hours  if they are completly changing at each refresh  then it means that your setup is wrong  APC is flushing everything   Allocate 20  more ram than what APC really use as a security margin  and check it on a regular basis   The default of allowing only 32MB is ridiculously low  PHP was designed when servers were 64MB and most scripts were using one php file per page  Nowadays solutions like Magento require more than 10k files   60Mb in APC   You should allow enough memory so most of php files are always cached  It s not a waste  it s more efficient to keep opcode in ram rather than having the corresponding raw php in file cache  Nowadays we can find dedicated servers with 24Gb of memory for as low as  80 month  so don t hesitate to allow several GB to APC  I put 2GB out of 24GB on a server hosting 5Magento stores and  40 wordpress website  APC uses 1 2GB  Count 64MB for Magento installation  40MB for a Wordpress with some plugins   Also  if you have developpment websites on the same server  Exclude them from cache

User · Answer

As Bokan has mentioned  you can up the memory if available  and he is right on how counter productive setting TTL to 0 is   NotE  This is how I fixed this error for my particular problem  Its a generic issue that can be caused by allot of things so only follow the below if you get the error and you think its caused by duplicate PHP files being loaded into APC   The issue I was having was when I released a new version of my PHP application  Ie replaced all my  php files with new ones APC would load both versions into cache   Because I didnt have enough memory for two versions of the php files APC would run out of memory   There is a option called apc stat to tell APC to check if a particular file has changed and if so replace it  this is typically ok for development because you are constantly making changes however on production its usually turned off as it was with in my case - http   www php net manual en apc configuration php ini apc stat  Turning apc stat on would fix this issue if you are ok with the performance hit   The solution I came up with for my problem is check if the the project version has changed and if so empty the cache and reload the page    define  PROJECT VERSION    0 28      if apc exists  MY APP VERSION           if apc fetch  MY APP VERSION      PROJECT VERSION           apc clear cache            apc store   MY APP VERSION   PROJECT VERSION           header  Location       http   empty   SERVER  HTTPS        s           SERVER  SERVER NAME     SERVER  REQUEST URI             exit            else      apc store   MY APP VERSION   PROJECT VERSION

User · Answer

Running the apc php script is key to understanding what your problem is  IMO  This helped us size our cache properly and for the moment  seems to have resolved the problem

User · Answer

I received the error  Unable to allocate memory for pool  after moving an OpenCart installation to a different server  I also tried raising the memory limit   The error stopped after I changed the permissions of the file in the error message to have write access by the user that apache runs as  apache  www-data  etc    Instead of modifying  etc group directly  or chmod-ing the files to 0777   I used usermod   usermod -a -G vhost-user-group apache-user   Then I had to restart apache for the change to take effect   apachectl restart   Or  sudo  etc init d httpd restart   Or whatever your system uses to restart apache   If the site is on shared hosting  maybe you must change the file permissions with an FTP program  or contact the hosting provider

User · Answer

For newbies like myself  these resources helped   Finding the apc ini file to make the changes recommended by c33s above  and setting recommended amounts  http   www untwistedvortex com optimizing-tuning-apc-alternate-php-cache   Understanding what apc ttl is  http   www php net manual en apc configuration php ini apc ttl  Understanding what apc shm size is  http   www php net manual en apc configuration php ini apc shm-size

User · Answer

To resolve this problem set value for apc shm size as integer  Locate your apc ini file  In my system apc ini file location  etc php5 conf d apc ini  and set  apc shm size   1000

[php] What is causing "Unable to allocate memory for pool" in PHP?

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