PHP Meminfo is a very simple PHP extension that gives you insight on the current content of the memory in PHP.
It's main goal is to understand memory leaks, but can be useful as well to get information on the behaviour of your application by looking at what data it produces in memory.
The main source of inspiration for this tool is the Java jmap tool with the -histo option (see man jmap)
For now, PHP Meminfo provides a list of live objects in memory with their class and handle.
- compiled and tested on PHP 5.4.4 (Debian 7)
MemInfo can be compiled outside PHP itself.
You will need the phpize command. It can be installed on a Debian based system by: apt-get install php5-dev
Once you have this command, follow this steps:
From the root of the extension directory:
phpize
./configure --enable-meminfo
make
cp modules/meminfo.so /path/to/your/extensions/folder
Add the following line to your php.ini or to a custom file inside /etc/php5/conf.d/ for Debian based system.
extension=meminfo.so
Restart your webserver.
Check the PHP Info output and look for the MemInfo data. If you can find it, installation has been successful.
To see the PHP Info output, just create a page calling the phpinfo(); function, a load it from your browser, or call php -i from command line.
All meminfo functions take a stream handle as a parameter. It allows you to specify a file (if needed with a variable name identified to your context), as well as uses standard output with the php://stdout stream.
Display size in byte of main data structs size in PHP. Will mainly differ between 32bits et 64bits environments.
meminfo_structs_size(fopen('php://stdout','w'));
It can be useful to understand difference in memory usage between two platforms.
Example Output on 64bits environment:
Structs size on this platform:
Class (zend_class_entry): 568 bytes.
Object (zend_object): 32 bytes.
Variable (zval): 24 bytes.
Variable value (zvalue_value): 16 bytes.
##List of currently active objects Provides a list of live objects with their class and their handle, as well as the total number of active objects and the total number of allocated object buckets.
meminfo_objects_list(fopen('php://stdout','w'));
For example:
Objects list:
- Class MyClassB, handle 2
- Class MyClassC, handle 5
- Class MyClassC, handle 6
- Class MyClassC, handle 7
Total object buckets: 7. Current objects: 4.
Note: It's a good idea to call the gc_collect_cycles() function before executing meminfo_objects_list(), as it will collect dead objects that has not been reclaimed by the ref counter due to circular references. See http://www.php.net/manual/en/features.gc.php for more details.
The examples/ directory at the root of the repository contains more detailed examples.
php examples/objects_list.php
Some simple shell one-liners can help you aggregate data from the dumped objects list to get a better grasp at what's happening:
-
Ordered list of number of objects per class
cat objects_list.meminfo | grep - | cut -d "," -f 1 | sort | uniq -c | sort -n
-
Top 5 of the most present class by objects number
cat objects_list.meminfo | grep - | cut -d "," -f 1 | sort | uniq -c | sort -nr | head -n 5
PHP Meminfo can be used in production, as it does not have any impact on performances outside of the call to the meminfo functions.
Nevertheless, production environment is not where you debug ;)
-
XDebug (http://www.xdebug.net) With the trace feature and the memory delta option (tool see XDebug documentation), you can trace function memory usage. You can use the provided script to get an aggregated view (TODO link)
-
PHP Memprof (https://github.com/arnaud-lb/php-memory-profiler) Provides aggregated data about memory usage by functions. Far less resource intensive than a full trace from XDebug.
Thanks to Derick Rethans on his inspiritionnal work on the essential XDebug. See http://www.xdebug.org/