Edit report at https://bugs.php.net/bug.php?id=63380&edit=1
ID: 63380
Updated by: rricha...@php.net
Reported by: tstarl...@php.net
Summary: Allocation via libxml does not use PHP's per-request
allocator
Status: Assigned
Type: Bug
Package: XML related
Operating System: Linux
PHP Version: master-Git-2012-10-29 (Git)
-Assigned To: rrichards
+Assigned To: tstarling
Block user comment: N
Private report: N
New Comment:
There is a major problem with doing this and why I didn't end tying into the
PHP
memory allocator. Depending upon setup, it is extremely likely to be able to
hit
memory corruption and/or mix memory allocations between modules. i.e. using
mod_perl and mod_php will cause PHP to override the libxml memory handling
functions (which are global) and bleed into mod_perl (or any others that are
using libxml2) causing any number of results (crashes, security issues, etc..).
The only way to be able to do something like this would be to make it compile
time option which is disabled by default allowing those who know their
environment intimately can utilize this at their own risk, Don't know if you
want to write a patch for that or not. Otherwise I don't see any way this could
safely be added,
Previous Comments:
------------------------------------------------------------------------
[2012-10-29 21:55:03] tstarl...@php.net
https://github.com/php/php-src/pull/223
------------------------------------------------------------------------
[2012-10-29 03:25:17] tstarl...@php.net
Description:
------------
Allocation via libxml does not use PHP's per-request allocator. So any memory
used by libxml will not be accounted against memory_get_usage() or memory_limit.
At Wikimedia we use libxml DOM trees to store wikitext parse trees, because
they are more compact in memory than the equivalent pure-PHP data structures.
When these parse trees are cached, the memory requirements can become
excessive, and the memory is typically not returned to the system after request
termination. Using xmlMemSetup() to set hook functions which use PHP's
per-request allocation functions will allow us to more effectively monitor and
limit the use of libxml in production.
I've developed a patch and will submit it to GitHub as a pull request.
Test script:
---------------
$doc = new DOMDocument;
for ( $i = 0; $i < 1000000 ; $i++ ) {
$doc->appendChild($doc->createElement('foo'));
}
print memory_get_usage()."\n";
Expected result:
----------------
312331440 (with debug and ZTS)
Actual result:
--------------
694256
------------------------------------------------------------------------
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Edit this bug report at https://bugs.php.net/bug.php?id=63380&edit=1
