Apache Memory consumption with MOD PHP?

[dcabbar]

I am running apache with mod_php, and have been trying to find out how much memory apache consumes. For this, wrote a very little script, which allocates 100 meg of string, and sleeps 240 seconds. Then, I hit this script from 5 browsers concurrently. And, measured memory consumption with free and top before running the test, during the test (during this 240 second sleep -- after about 60 seconds), and after tests are finished (php script exit)

This test should have allocated 450-500 megs in total, but for some reason, I can only see about 100 megs when I use free. And, top shows about 110 megs...

Am I doing something wrong here? Why can't I see this 500 megs and/or how can I see it?

Thanks.

free RESULTS 
  total used free shared buffers cached 
BEFORE RUNNING THE TESTS: 
Mem: 1035436 989896 45540  0 89892 780480 
Swap: 2056300 295640 1760660 
DURING THE TESTS (AFTER MEMORY ALLOCATION, PHP STILL IS IN SLEEP): 
Mem: 1035436 1021228 14208  0 90692 721304 
Swap: 2056300 297080 1759220 
AFTER TESTS ARE COMPLETED (PHP SCRIPT IS FINISHED) 
Mem: 1035436 895352 140084  0 87944 686372 
Swap: 2056300 297312 1758988 
top -b -n 1 RESULTS: 
 PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND         
BEFORE RUNNING THE TESTS: 
28917 root 18 0 25584 9872 5928 S 0.0 1.0 0:00.09 httpd          
28919 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28920 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28921 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28922 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28923 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28924 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28925 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28926 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
DURING THE TESTS (AFTER MEMORY ALLOCATION, PHP STILL IS IN SLEEP): 
28917 root 18 0 25584 9872 5928 S 0.0 1.0 0:00.09 httpd          
28919 apache 18 0 110m 91m 2248 S 0.0 9.1 0:00.29 httpd          
28920 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28921 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28922 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28923 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28924 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28925 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28926 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd  
AFTER TESTS ARE COMPLETED (PHP SCRIPT IS FINISHED) 
28917 root 18 0 25584 9872 5928 S 0.0 1.0 0:00.09 httpd          
28919 apache 18 0 25672 6376 2356 S 0.0 0.6 0:00.31 httpd          
28920 apache 18 0 25672 6376 2356 S 0.0 0.6 0:00.32 httpd          
28921 apache 18 0 25672 6376 2356 S 0.0 0.6 0:00.33 httpd          
28922 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28923 apache 17 0 25672 6376 2356 S 0.0 0.6 0:00.32 httpd          
28924 apache 18 0 25672 6376 2356 S 0.0 0.6 0:00.27 httpd          
28925 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd          
28926 apache 25 0 25584 4972 1004 S 0.0 0.5 0:00.00 httpd  
SCRIPT: 
ini_set("memory_limit","256m"); 
$aa = array(); 
$total = 0; 
for ($i = 0; $i < 9; $i++) { 
 $tc = chr(rand(65, 85)) . chr(rand(65, 85)) .chr(rand(65, 85)) .chr(rand(65, 85)) .chr(rand(65, 85)); 
 $aa[$i] = str_repeat($tc, 2000000); 
 $total += strlen($aa[$i]); 
} 
print "<h1>$total</h1>"; 
sleep(240);