ID: 39736 User updated by: cnww at hfx dot andara dot com Reported By: cnww at hfx dot andara dot com -Status: Bogus +Status: Open Bug Type: Arrays related Operating System: Debian GNU/Linux PHP Version: 5.2.0 New Comment:
Yes, obviously the serialized string can be larger than the array in memory. The issue here is that when you get a sufficiently complex array the memory required to serialize suddenly balloons out to SEVERAL HUNDRED TIMES the size of the array. Just for the heck of it I created some more swap space and tried this again with a memory limit of 4GB (actually 4095MB, apparently PHP cannot handle 4096), this allowed the serialize() call to succeed. It eventually produced a 6.8MB output string (7,147,979 characters to be exact), and the PHP process' peak memory usage while creating this 6.8MB string was 1,540MB of RAM. So what is it doing with a ~7MB of data that requires over 1.5GB of RAM? I may be missing something, but at the moment I do not see any reason why the memory requirement for serialize() ought to be anything more than O(n) on the size of the input. I had a look at the source in var.c, but nothing jumps out at me as an obvious problem. My best guess based on the symptoms is that it's somehow copying the buffer and/or hash table when recursing through an array of arrays. If this really isn't a bug then I apologize for wasting your time. I'll polish my own serialize() function a bit and post it as a comment in the function reference for other people running into this problem. Previous Comments: ------------------------------------------------------------------------ [2006-12-04 21:26:09] [EMAIL PROTECTED] Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php serialize() representation of the data is quite a bit larger then it's representation in memory. So a 60mb array could easily take 120-180 megs as a serialized string. ------------------------------------------------------------------------ [2006-12-04 21:24:28] cnww at hfx dot andara dot com Description: ------------ When called on a tree implemented as a multi-dimensional array occupying something like 60MB of RAM serialize fails with an error like: Fatal error: Allowed memory size of 1073741824 bytes exhausted (tried to allocate 6282420 bytes) in /var/www/lib/metacache.php on line 105 So either the memory allocation system is busted or the serialization of ~60MB of data (actually the full text version is only 9.1MB) requires over 1GB of memory. Reproduce code: --------------- The line that is actually failing is: $meta_ser = serialize( &$metacache_buf ); For obvious reasons I have not posted the whole array here. I created an example program that reproduces the problem using an array of 242,919 strings made with var_export() from the directory listing of a Windows machine's D: drive. You can get the code from: http://arachne.k-pcltee.com/~cnww/serialbug.bz2 The example program seems to require around 52MB of RAM to create the array, so if you're using the default 8MB limit it will fail before it gets to the serialize() call. Any limit of 64MB or greater seems to result in it failing during serialize(). Expected result: ---------------- It should print "Exiting normally" Actual result: -------------- Fatal error: Allowed memory size of 1073741824 bytes exhausted (tried to allocate 6010844 bytes) in /tmp/serialbug.php on line 313030 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=39736&edit=1
