memory_get_usage

Alex Aulbach (2011-03-22 01:14:20)

Note, that the official IEC-prefix for kilobyte, megabyte and so on are KiB, MiB, TiB and so on.
See http://en.wikipedia.org/wiki/Tebibyte
At first glance this may sound like "What the hell? Everybody knows, that we mean 1024 not 1000 and the difference is not too big, so what?". But in about 10 years, the size of harddisks (and files on them) reaches the petabyte-limit and then the difference between PB and PiB is magnificent.
Better to get used to it now. :)

John Lim (2010-11-30 02:45:36)

It is claimed that this function calls the PHP memory garbage collector by some of the commenters.
A quick check of the source code (PHP 5.2.9) shows that this function does not do any garbage collection.
From var.c:
ZEND_API size_t zend_memory_usage(int real_usage TSRMLS_DC)
{
if (real_usage) {
return AG(mm_heap)->real_size;
} else {
#if MEMORY_LIMIT
return AG(mm_heap)->size;
#else
return AG(mm_heap)->real_size;
#endif
}
}
And from zend_alloc.c
/* {{{ proto int memory_get_usage([real_usage])
Returns the allocated by PHP memory */
PHP_FUNCTION(memory_get_usage) {
zend_bool real_usage = 0;
if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "|b", &real_usage) == FAILURE) {
RETURN_FALSE;
}

RETURN_LONG(zend_memory_usage(real_usage TSRMLS_CC));
}
/* }}} */

lorin dot weilenmann at gmail dot com (2010-11-26 01:37:55)

I can confirm that this function triggers a garbage collection. I have a script that exceeded 128MB of memory at some point and ended with a fatal error. I was confused, because the script dealt with some large files initially, but the memory load from that point on should have been marginal, and the error occurred at the very end.
Those large files were dealt in a dedicated function and i even used unset() on the variable holding the file after the file was written to disk inside that function. So the memory should have been cleared twice, first after the unset() call, and second once the function ended.
To debug the memory usage, I called memory_get_usage(true) at some points and echo-ed the memory allocation. Just by adding a few echos here and there in the script, the memory usage never exceeded 1MB overhead (on top of the current file size) and the memory error disappeared.

xelozz -at- gmail.com (2010-02-18 02:34:53)

To get the memory usage in KB or MB

<?php
function convert($size)
 {
    $unit=array('b','kb','mb','gb','tb','pb');
    return @round($size/pow(1024,($i=floor(log($size,1024)))),2).' '.$unit[$i];
 }

echo convert(memory_get_usage(true)); // 123 kb
?>

mario (2009-11-16 09:11:32)

not sure how this works internally but I have observed sort of side effects here: calling this function apparently triggers PHP's "garbage collector" -- and frees some memory. I managed to "fix" some savagely coded mess of a web application solely by calling this function just before the code that would usually throw out-of-memory errors. the php version there was 5.2.10

jeff dot peck at snet dot net (2009-08-19 09:22:19)

To get the memory usage in KB or MB

<?php
    function echo_memory_usage() {
        $mem_usage = memory_get_usage(true);
        
        if ($mem_usage < 1024)
            echo $mem_usage." bytes";
        elseif ($mem_usage < 1048576)
            echo round($mem_usage/1024,2)." kilobytes";
        else
            echo round($mem_usage/1048576,2)." megabytes";
            
        echo "<br/>";
    }
?>

miteigi nemoto (miteigi at yandex dot ru) (2008-11-18 20:19:05)

Decision a memory_get_usage problem for windows system

Tested OS: Windows XP
Server: Apache

PHP must be loaded as CGI to get correctly memory usage by Process ID ( getmypid() ) and with cmd-tools like tasklist.exe

PHP as CGI have your own PID instead constant Apache PID and you get a true memory size independed form Apache memory usage.

Configure in httpd.conf of Apache:

1. Comment the line like this:
LoadModule php4_module "/usr/local/php/sapi/php4apache.dll"
or
LoadModule php5_module "/usr/local/php5/php5apache.dll"

2. Add this and edit your path to php:
<Directory "z:/usr/local/php">
  Options ExecCGI
</Directory>
ScriptAlias "/__php_dir__/" "z:/usr/local/php/"
Action application/x-httpd-php "/__php_dir__/php.exe"

3. Restart Apache

Use this PHP-code:

<?php
/**
* A memory_get_usage() for Windows System, wich compiled without --enable-memory-limit 
* PHP must be loaded as CGI
* Greetings form miteigi nemoto
* @return string
*/
function memory_get_usage_by_tasklist()
{
    $output = array();
    exec( 'tasklist ', $output );
    foreach ($output as $value)
    {
        $ex=explode(" ",$value);
        $count_ex=count($ex);
        if (eregi(" ".getmypid()." Console",$value))
        {
            $memory_size=$ex[$count_ex-2]." Kb";
            return $memory_size;
        }
    }
}
echo memory_get_usage_by_tasklist();
?>

joe at schmoe dot com (2006-12-23 00:44:41)

the various memory_get_usage replacements here don't seem to work on Mac OS X 10.4(Intel)

I got it to work like this...

<?php
function memory_get_usage()
{
     $pid = getmypid(); 
     exec("ps -o rss -p $pid", $output);
     return $output[1] *1024;
}
?>

e dot a dot schultz at gmail dot com (2006-04-08 16:41:44)

This is a function that should work for both Windows XP/2003 and most distrabutions of UNIX and Mac OS X. 

<?php
if( !function_exists('memory_get_usage') )
{
    function memory_get_usage()
    {
        //If its Windows
        //Tested on Win XP Pro SP2. Should work on Win 2003 Server too
        //Doesn't work for 2000
        //If you need it to work for 2000 look at http://us2.php.net/manual/en/function.memory-get-usage.php#54642
        if ( substr(PHP_OS,0,3) == 'WIN') 
        {
               if ( substr( PHP_OS, 0, 3 ) == 'WIN' )
                {
                    $output = array();
                    exec( 'tasklist /FI "PID eq ' . getmypid() . '" /FO LIST', $output );
        
                    return preg_replace( '/[\D]/', '', $output[5] ) * 1024;
                }
        }else
        {
            //We now assume the OS is UNIX
            //Tested on Mac OS X 10.4.6 and Linux Red Hat Enterprise 4
            //This should work on most UNIX systems
            $pid = getmypid();
            exec("ps -eo%mem,rss,pid | grep $pid", $output);
            $output = explode("  ", $output[0]);
            //rss is given in 1024 byte units
            return $output[1] * 1024;
        }
    }
}
?>

grey - greywyvern - com (2005-08-17 12:37:37)

If nothing else in the user notes below works for you, you can get a very (VERY) rough estimate of PHP memory usage by outputting the $GLOBALS array, stripping it of indentation whitespace, and counting the characters in the resulting string.  This method has a very high overhead (to be expected), but works on all operating systems, regardless of whether or not they have the --enable-memory-limit config option set.  I find that the syntax overhead of the print_r() statement roughly accounts for the PHP runtime base memory usage.

The code below is set up to work on all arrays, not just the $GLOBALS array.  Keep in mind that outside data referenced by resource IDs, such as database results and open file data, is not included in this total.

<?php

function array_size($arr) {
  ob_start();
  print_r($arr);
  $mem = ob_get_contents();
  ob_end_clean();
  $mem = preg_replace("/\n +/", "", $mem);
  $mem = strlen($mem);
  return $mem;
}

$memEstimate = array_size($GLOBALS);

?>

Use only if being off to either side by at least 20% is acceptible for your purposes.

vesa dot kivisto at nepton dot fi (2005-07-14 06:02:47)

[EDIT by danbrown AT php DOT net: This function will only extend Windows versions of PHP where the server has the required third-party software.]

I was unable to get the previous examples working properly and created code which works at least for me. Enjoy!

<?php
// Please note that you'll need the pslist.exe utility from http://www.sysinternals.com/Utilities/PsTools.html
// This is because win/2000 itself does not provide a task list utility.
//
function getMemoryUsage() {

 // try to use PHP build in function
 if( function_exists('memory_get_usage') ) {
  return memory_get_usage();
 }

 // Try to get Windows memory usage via pslist command
 if ( substr(PHP_OS,0,3) == 'WIN') {
  
  $resultRow = 8;
  $resultRowItemStartPosition = 34;
  $resultRowItemLength = 8;
  
  $output = array();
  exec('pslist -m ' . getmypid() , $output);
    
  return trim(substr($output[$resultRow], $resultRowItemStartPosition, $resultRowItemLength)) . ' KB';
  
 }

 
 // No memory functionality available at all
 return '<b style="color: red;">no value</b>';
  
}
?>

guenter_doege at web dot de (2005-07-10 23:28:58)

The Win XP / 2003 workaround script will also work with windows 2000 with a few slight modifications.

Please note that you'll need the pslist.exe utility from http://www.sysinternals.com/Utilities/PsTools.html because win/2000 itself does not provide a task list utility.

<?php

function getMemUsage()
{
     
       if (function_exists('memory_get_usage'))
       {
           return memory_get_usage();
       }
       else if ( substr(PHP_OS,0,3) == 'WIN')
       {
           // Windows 2000 workaround

           $output = array(); 
           exec('pslist ' . getmypid() , $output); 
           return trim(substr($output[8],38,10));
       }
       else
       {
           return '<b style="color: red;">no value</b>';
       }
}
?>

MagicalTux at FF dot st (2005-05-25 00:08:10)

When you need to get the OS, do not use $_SERVER['OS'] or $_ENV['OS'], better use PHP_OS constant !
<?php
if (substr(PHP_OS,0,3)=='WIN') {
  // [...]
}
?>

You also have other values such as CYGWIN_NT-5.0, Linux, ... this is the best way to get system's os (anyone on linux can do an "export OS=windows")

webNOSPAMsjwans at hotmail dot com (2004-12-01 07:09:52)

A quick and dirty Windows XP / 2003 wordaround:

<?php 

function getMemUsage()
{
        
        if (function_exists('memory_get_usage'))
        {
            return memory_get_usage();
        }
        else if ( strpos( strtolower($_SERVER["OS"]), 'windows') !== false)
        {
            // Windows workaround
            $output = array();
            
            exec('tasklist /FI "PID eq ' . getmypid() . '" /FO LIST', $output);            
            return substr($output[5], strpos($output[5], ':') + 1);
        }
        else
        {
            return '<b style="color: red;">no value</b>';
        }
}

?>

randolphothegreat at yahoo dot com (2004-11-29 13:37:06)

[EDIT by danbrown AT php DOT net: This is intended by the author to only be used with PHP 4 < 4.3.2.]

I'd just like to point out that although sandeepc at myrealbox dot com's idea for displaying the current memory usage is a good one, it's perhaps a bad idea to pipe the entire process list through grep. A better performing method would be to select only the process we're interested in:

<?php
$pid = getmypid();
error_log('MEMORY USAGE (% KB PID ): ' . `ps --pid $pid --no-headers -o%mem,rss,pid`);
?>

True, it's not much of a performance boost, but every bit helps.

ad-rotator.com (2004-05-14 10:31:16)

The method sandeepc at myrealbox dot com posted yields larger memory usage, my guess is that it includes all the PHP interpreter/internal code and not just the script being run.
1) Use ps command
MEMORY USAGE (% KB PID ): 0.8 12588 25087 -> about 12MB
2) Use memory_get_usage()
int(6041952) -> about 6MB