On 03/06/2007 12:34 AM, Brian Moon wrote:
Ok, I am no C coder and I don't claim to be very smart about low level
parts of PHP. But, IMO, this is bug.
http://bugs.php.net/bug.php?id=36924
I have created a test script that shows the insanity of this bug:
<?php
$str = "This is a medium length string";
$start = memory_get_usage();
for($x=1;$x<=100;$x++){
echo $str.": (3.5): ".time()."\n";
}
$first_growth = number_format(memory_get_usage() - $start);
$start = memory_get_usage();
for($x=1;$x<=100;$x++){
echo "$str: (3.5): ".time()."\n";
}
$growth = number_format(memory_get_usage() - $start);
echo "first growth: $first_growth\nsecond growth: $growth\n";
?>
Number of iterations | First growth | Second growth | Peak usage
100 480 bytes ~5Kb ~73Kb
100 000 556 bytes ~32Kb ~100Kb
1 000 000 556 bytes ~32Kb ~100Kb
Tested with PHP 5.2.1 and 5.2.2-dev on Linux (with --disable-debug).
Now, you turn that into a script that is going to loop millions of
times, building strings to build data and run for hours. The next thing
you know, your cron job is using 450MB of memory and you try to figure
out what YOU did wrong. Hours later you find this little jewel waiting
for you and realize you did not do anything wrong. You just used the
language.
Yup, the language stole ~32Kb of your memory and used it to speedup the
allocation of small chunks.
Everyone ignored my last email about memory waste and large arrays. I
can only assume that you will ignore this one too.
I am starting to see why Stefan became so bitter.
I have always tried to squash the "myth" that putting variables inside
strings in PHP was bad, but now, I think I will flip on that.
I tested as far back as PHP 4.3.9 and as new as 5.2.1.
--
Wbr,
Antony Dovgal
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