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@Danack
Last active July 12, 2019 22:33
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An example of how creating cycles in variables leads to
Without manually calling gc_collect_cycles()
============================================
Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 139264 bytes) in - on line 27
GC Statistics
-------------
Runs: 0
Collected: 0
Root buffer length: 254
Root buffer peak: 260
Possible Remove from Marked
Root Buffered buffer grey
-------- -------- ----------- ------
ZVAL 261 260 6 0
ZOBJ 0 0 0 0
Manually calling gc_collect_cycles()
====================================
Max memory that should be 'live' is 5120 kB
used: 358688 | allocated: 524288 | peak: 786432
GC Statistics
-------------
Runs: 1000
Collected: 2000
Root buffer length: 0
Root buffer peak: 5
Possible Remove from Marked
Root Buffered buffer grey
-------- -------- ----------- ------
ZVAL 1007 1007 6 2002
ZOBJ 0 0 0 0
<?php
$performGC = false;
if ($performGC) {
echo "GC collection will be done - app should not crash.\n";
}
else {
echo "GC collection won't be done - app should crash.\n";
}
$dataSizeInKB = 128;
//Change this line if you tweak the parameters above.
ini_set('memory_limit', "64M");
for ($y=0 ; $y<$dataSizeInKB ; $y++) {
for ($x=0 ; $x<32 ; $x++) { //1kB
$memData .= md5(time() + (($y * 32) + $x));
}
}
file_put_contents("memdata.txt", $memData);
// This function creates a cyclic variable loop
function useSomeMemory($x) {
$data = [];
$data[$x] = file_get_contents("memdata.txt");
$data[$x + 1] = &$data;
};
for($x=0 ; $x<1000 ; $x++) {
useSomeMemory($x);
if ($performGC == true) {
gc_collect_cycles();
}
}
printf("\nused: %10d | allocated: %10d | peak: %10d\n",
memory_get_usage(),
memory_get_usage(true),
memory_get_peak_usage(true)
);
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