Capturing (externally) the memory consumption of a given Callback

Question

The Problem

Lets say I have this function:

function hog($i = 1) // uses $i * 0.5 MiB, returns $i * 0.25 MiB
{
    $s = str_repeat(\'a\', $i * 1024 *          


        

Answer 1

I was digging in the PHP manual and I found the memtrack extension, not perfect but it's something.

---

EDIT: I had heard about it, but never actually tried it before. Turns out XHProf is all I needed:

$flags = array
(
    XHPROF_FLAGS_CPU,
    XHPROF_FLAGS_MEMORY,
    XHPROF_FLAGS_NO_BUILTINS,
);

$options = array
(
    'ignored_functions' => array
    (
        'call_user_func',
        'call_user_func_array',
        'xhprof_disable',
    ),
);

function hog($i = 1) // uses $i * 0.5 MiB, returns $i * 0.25 MiB
{
    $s = str_repeat('a', $i * 1024 * 512); return substr($s, $i * 1024 * 256);
}

---

Test #1:

xhprof_enable(array_sum($flags), $options);

hog(4);

$profile = xhprof_disable();

print_r($profile);

Output:

    [main()==>hog] => Array
        (
            [ct] => 1
            [wt] => 54784
            [mu] => 384
            [pmu] => 3142356
        )

    [main()] => Array
        (
            [ct] => 1
            [wt] => 55075
            [mu] => 832
            [pmu] => 3142356
        )

mu is memory usage, pmu is peak memory usage, 3142356 / 1024 / 1024 / 0.5 = 4 = $i.

---

Test #2 (without XHPROF_FLAGS_NO_BUILTINS):

    [hog==>str_repeat] => Array
        (
            [ct] => 1
            [wt] => 21890
            [cpu] => 4000
            [mu] => 2097612
            [pmu] => 2094200
        )

    [hog==>substr] => Array
        (
            [ct] => 1
            [wt] => 17202
            [cpu] => 4000
            [mu] => 1048992
            [pmu] => 1048932
        )

    [main()==>hog] => Array
        (
            [ct] => 1
            [wt] => 45978
            [cpu] => 8000
            [mu] => 1588
            [pmu] => 3143448
        )

    [main()] => Array
        (
            [ct] => 1
            [wt] => 46284
            [cpu] => 8000
            [mu] => 2132
            [pmu] => 3143448
        )

Whoohoo! Thanks Facebook!

---

From the XHProf docs:

It is worth clarifying that that XHProf doesn't strictly track each allocation/free operation. Rather it uses a more simplistic scheme. It tracks the increase/decrease in the amount of memory allocated to PHP between each function's entry and exit. It also tracks increase/decrease in the amount of peak memory allocated to PHP for each function.