PHP Unable to Allocate Memory – Solutions

apache-2.2linuxopenvz

On my way to the office this morning, every website on our shared VPS started giving the same error (several times, not the typical memory_limit error which is fatal):

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

The shared server is a 64-bit OpenVZ container running cPanel. There are only ~6 VPSes on the host– this is the largest one at only 4GB. The host itself has 24GB RAM. As the below graphs show, the memory usage on the host and VPS are both rather low. CPU Usage/Disk/Host all seem to be normal. RlimitMem was set to 583653034, yet the memory usage is about the same as it usually is.

Apache 2.2, PHP 5.2 (mod_php)

Restarting Apache has corrected the problem for now. However, I'd like to prevent it from happening again and I'm not sure what was limiting the memory. RlimitMem was set to 583653034, yet the memory usage is about the same as it usually is. There's seems to be plenty of memory: what caused this error?

VPS Memory Usage

shared vm memory usage, hovering around 50%

Host Memory Usage

host vm memory usage, used hovering at 20%, cached at 65% until 6AM, where it dropped to ~60%, buffered at ~10%

APC Information

 apc.ttl=0
 apc.shm_size=0
 apc.mmap_file_mask=(blank)

1 Segment(s) with 32.0 MBytes
(mmap memory, pthread mutex locking)

Best Answer

That is definitely the error you get when APC runs out of memory. When I (re)build servers, I often forget to increase this value to 128 M (suitable for my application) and that is the exact error you see.

Related Solutions

Linux – Memory usage of php-cgi processes is growing steadily

Try to lower down var_size. If we had value at 64MB, after a few hours it started to swap a lot, and after next few hours it was completely down. Try to keep original settings at 32M, maybe this should help you a lot - we had the same problem at our travel site Xcache is still a lot of buggy software :(

PHP – Unable to Remove Limit on Memory Usage for PHP Script

Background:

I just grabbed the current version of Piwik -- In version 1.5, line 969 appears as:

public function addRowsFromSerializedArray( $stringSerialized )
{
    $serialized = unserialize($stringSerialized);
    if($serialized === false)
    {
        throw new Exception("The unserialization has failed!");
    }
    $this->addRowsFromArray($serialized);
}

and is specifically $serialized = unserialize($stringSerialized);. The call to unserialize can be incredibly memory intensive. There is an excellent post here.

As you've noted, this clearly isn't a bug in your script and is a valid Out of Memory.

Suggestion: In the config file, as noted above in my comment:

/.../piwik/config/global.ini.php

I think you may need to increase one of these limits:

# during archiving, Piwik will limit the number of results recorded, for performance reasons
# maximum number of rows for any of the Referers tables (keywords, search engines, campaigns, etc.)
# this limit will also be applied to the Custom Variables names and values reports
datatable_archiving_maximum_rows_referers = 1000
# maximum number of rows for any of the Referers subtable (search engines by keyword, keyword by campaign, etc.)
datatable_archiving_maximum_rows_subtable_referers = 50

# maximum number of rows for any of the Actions tables (pages, downloads, outlinks)
datatable_archiving_maximum_rows_actions = 500
# maximum number of rows for pages in categories (sub pages, when clicking on the + for a page category)
# note: should not exceed the display limit in Piwik_Actions_Controller::ACTIONS_REPORT_ROWS_DISPLAY
#       because each subdirectory doesn't have paging at the bottom, so all data should be displayed if possible.
datatable_archiving_maximum_rows_subtable_actions = 100

# maximum number of rows for other tables (Providers, User settings configurations)
datatable_archiving_maximum_rows_standard = 500

where I changed the semi-colons to # signs just to make sf's autocolor readable.

You might also try adding:

CMD_TO_CHECK_SETTINGS="$PHP_BIN -i > /tmp/piwik-php-env.out"
$CMD_TO_CHECK_SETTINGS

to archive.sh to determine if there are other settings afoot which override the php.ini file.

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