PHP memory profiler extension
C M4
Latest commit ad6d84b May 25, 2016 @arnaud-lb Update README.md

README.md

php-memprof

php-memprof profiles memory usage of PHP scripts, and especially can tell which function has allocated every single byte of memory currently allocated.

This is different from measuring the memory usage before and after a function call:

<?php

// script 1

function a() {
    $data = file_get_contents("huge-file");
}

a();

$profile = memprof_dump_array();

In script 1, a before/after approach would designate file_get_contents() as huge memory consumer, while the memory it allocates is actually freed quickly after it returns. When dumping the memory usage after a() returns, the memprof approach would show that file_get_contents() is a small memory consumer since the memory it allocated has been freed at the time memprof_dump_array() is called.

<?php

// script 2

function a() {
    global $cache;
    $cache = file_get_contents("huge-file");
}

a();

$profile = memprof_dump_array();

In script 2, the allocated memory remains allocated after file_get_contents() and a() return, and when memprof_dump_array() is called. This time a() and file_get_contents() are shown as huge memory consumers.

How it works

See INTERNALS.md

Dependencies

  • Judy Library (e.g. libjudy-dev or judy package)
  • C Library with malloc hooks (optional; allows to track persistent allocations too)

Install

Using PECL

pecl install memprof

Manually

Download the source and run the following commands in the source directory:

phpize
./configure
make
make install

Loading the extension

The extension can be loaded on the command line, just for one script:

php -dextension=memprof.so script.php

Or permanently, in php.ini:

extension=memprof.so

Usage

Memprof can be enabled during script execution by calling memprof_enable().

Then the memory usage can be dumped by calling one of the memprof_dump_ functions. Both tell which functions allocated all the currently allocated memory.

Example:

<?php

if (function_exists('memprof_enable')) {
    memprof_enable();
}

do_some_work();

if (function_exists('memprof_enable')) {
    memprof_dump_callgrind(fopen("/tmp/callgrind.out", "w"));
}

memprof_enabled()

Returns whether memprof is enabled.

memprof_enable()

Enables memprof and start tracking memory allocations. Note: any memory allocation made before this call is ignored.

memprof_disable()

Disables memprof and forget previous allocations.

memprof_dump_callgrind(resource $stream)

The memprof_dump_callgrind function dumps the current memory usage to a stream in callgrind format. The file can then be read with tools such as KCacheGrind or QCacheGrind.

<?php
memprof_dump_callgrind(fopen("output", "w"));

Here is a KcacheGrind screenshot:

KCacheGrind screenshot

memprof_dump_pprof(resource $stream)

The memprof_dump_pprof function dumps the current memory usage to a stream in pprof format.

<?php
memprof_dump_pprof(fopen("profile.heap", "w"));

The file can be visualized using google-perftools's pprof tool.

Display annotated call-graph in web browser or in gv:

$ pprof --web profile.heap
$ # or:
$ pprof --gv profile.heap

pprof call-graph screenshot

Output one line per function, sorted by own memory usage:

$ pprof --text profile.heap

memprof_dump_array()

<?php
$dump = memprof_dump_array();

The dump exposes the following information:

  • Inclusive and exclusive memory usage of functions (counting only the memory that has is still in use when memprof_dump_array is called)
  • Inclusive and exclusive blocks count of functions (number of allocated; counting only the blocks that are still in use when memprof_dump_array is called)
  • The data is presented in call stacks. This way, if a function is called from multiple places, it is possible to see which call path caused it to leak the most memory

Example output:

Array
(
  [memory_size] => 11578
  [blocks_count] => 236
  [memory_size_inclusive] => 10497691
  [blocks_count_inclusive] => 244
  [calls] => 1
  [called_functions] => Array
    (
      [main] => Array
        (
          [memory_size] => 288
          [blocks_count] => 3
          [memory_size_inclusive] => 10486113
          [blocks_count_inclusive] => 8
          [calls] => 1
          [called_functions] => Array
            (
              [a] => Array
                (
                  [memory_size] => 4
                  [blocks_count] => 1
                  [memory_size_inclusive] => 10485825
                  [blocks_count_inclusive] => 5
                  [calls] => 1
                  [called_functions] => Array
                    (
                      [b] => Array
                        (
                          [memory_size] => 10485821
                          [blocks_count] => 4
                          [memory_size_inclusive] => 10485821
                          [blocks_count_inclusive] => 4
                          [calls] => 1
                          [called_functions] => Array
                            (
                              [str_repeat] => Array
                                (
                                  [memory_size] => 0
                                  [blocks_count] => 0
                                  [memory_size_inclusive] => 0
                                  [blocks_count_inclusive] => 0
                                  [calls] => 1
                                  [called_functions] => Array
                                    (
                                    )
                                )
                            )
                        )
                    )
                )
              [memprof_dump_array] => Array
                (
                  [memory_size] => 0
                  [blocks_count] => 0
                  [memory_size_inclusive] => 0
                  [blocks_count_inclusive] => 0
                  [calls] => 1
                  [called_functions] => Array
                    (
                    )
                )
            )
        )
    )
)

PHP 7

php-memory-profiler does not support PHP 7 yet

Todo

  • PHP 7 support
  • Support for tracking persistent (non-zend-alloc) allocations when libc doesn't have malloc hooks